[{"ID":392,"Name":"Shishaldin 1999/9","Description":"   From Neal and others (2004): \"Following anomalous, post-eruption seismicity of late December 1999, a series of seismic events caused by small explosions were identified on January 15, 2000. No associated plumes or thermal anomalies appeared on satellite images. Re-analysis of seismic data for the previous several months revealed that similar small 'explosion' seismic signals had been occurring intermittently since September 1999, several months after the end of the main phase of the 1999 eruptive activity (Nye and others, 2002). The January events were low-level and difficult to discern during the frequently inclement weather when background noise was high. The explosions prompted AVO to mention the change in the weekly update, however, the level of concern color code remained GREEN (table 4.) On January 28 and 29, vigorous steam plumes were observed rising up to about 3,000 ft (1,000 m) over Shishaldin. By early February, the frequency and amplitude of the overall seismicity, including the explosion events, had increased (up to 200 per day) and were accompanied by reports of vigorous steam plumes. The activity was interpreted to be small phreatic explosions within the cone's deep central crater. Noting that a similar pattern had developed in February 1999 prior to the onset of strombolian eruptive activity, AVO upgraded the color code to YELLOW on February 3. Fortuitously, the number of seismic events abruptly decreased the next day.  The color code was lowered to GREEN on February 18. A small steam plume was observed in satellite images on February 22 that extended 15-20 km (9-12 mi) east of the volcano, and small, low-frequency seismic events continued through the spring.\r\n   \"Satellite analysis detected a few weak thermal anomalies in the summit crater through the spring and summer of 2000. On occasion, steam plumes extended up to 15 km (9 mi) from the summit.  In early May, a significant increase in the number of small, low-frequency earthquakes was recorded, however no attendant change in thermal character or visual observations was noted, and\r\nseismicity declined by the end of summer. AVO mentioned both the seismicity and thermal anomalies in weekly updates for a period of one month, but remained at Level of Concern Color Code GREEN for the remainder of the year.\"","StartYear":1999,"StartMonth":9,"StartDay":25,"StartTime":null,"StartQualifier":10,"StartQualifierUnit":"Days","EndYear":2000,"EndMonth":2,"EndDay":4,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":"","Volcano":"Shishaldin","ParentVolcano":"Shishaldin","VolcanoID":"ak252","ParentVolcanoID":"ak252"},{"ID":156,"Name":"Makushin 2000/7","Description":"   From McGimsey and others (2004): \"On February 22, 2001, pilot Joe Polanco reported smelling sulfur and seeing steam issuing from the summit area of Makushin as he flew by.  Over the next several months, as tremor from the eruption of Cleveland volcano, 230 km (~145 mi) to the west was being recorded on the Makushin network, AVO seismologists began to suspect that some of the seismicity was actually being generated at Makushin.  By May, 2001, it was determined that a real increase in seismic activity beneath Makushin had begun in July, 2000, and on June 1, 2001, AVO included Makushin in the Weekly Update.  Earthquakes ranging in magnitude from 0 to 1.5 were occurring at a depth of between 0 and 8 km.  AVO continued to closely monitor the activity, which became intermittent by mid-summer and slowly faded back down to background levels through the fall months.\"","StartYear":2000,"StartMonth":7,"StartDay":null,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":"","EndYear":2001,"EndMonth":6,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":"","Volcano":"Makushin","ParentVolcano":"Makushin","VolcanoID":"ak188","ParentVolcanoID":"ak188"},{"ID":520,"Name":"Pavlof 2001/1","Description":"   McGimsey and others (2004) summarize 2001 steaming and other activity at Pavlof as follows: \"Principal/Teacher, John Concilius, has a good view of Pavlof from his home in Nelson Lagoon. On January 20, 2001 he observed through binoculars steaming from multiple locations near the summit, but none actually at the top of the volcano. He reported that the steam was white and not discolored, and, that the snow near the summit was clean with no evidence of melting.\r\n   \"He concluded by stating that this was the most steaming he had seen at the volcano during the past several years and that other villagers considered the steaming to be unusual.AVO remote sensing specialist Dave Schneider analyzed Advanced Very High Resolution Radiometer (AVHRR) satellite images taken from January 18 to 22, 2001 and found no evidence of increased thermal activity at the volcano and no unusual seismicity was noted. No further reports of steaming were forthcoming. This may have been a meteorological phenomenon.While working in Cold Bay in early June, Martin LaFevers, Seismic Data Manager at UAFGI, observed and photographed the summit of Pavlof during a weather break; it appeared to be covered with ash. A local pilot reported seeing 'something other than steam' at the summit. Again, there was no indication of anomalous seismicity.\r\n   \"NWS observers in Cold Bay contacted AVO on the morning of November 7, 2001 to report a small steam plume originating from the south side of Pavlof; they also received several Pilot Weather Reports (PIREPS) describing the same observation. About a month later, on December 13, 2001, NWS personnel in Cold Bay reported steam issuing from a point about half-way down the south flank of the volcano. The plume rose to a height of about 6,000 ft (~1,830 m) before dissipating. A Pen Air pilot corroborated the report and added that the steaming was coming from a 'hill' on the southwest flank; this pilot added that he encountered a strong sulfur smell on a flight by the volcano that day. AVO detected no unusual seismicity or thermal anomalies. Based on conversations with the Pen Air pilot, AVO determined that the source of steaming was likely the fumarole field on nearby Mt. Hague, a late Pleistocene volcano with no historic activity.\"","StartYear":2001,"StartMonth":1,"StartDay":20,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2001,"EndMonth":12,"EndDay":13,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Pavlof","ParentVolcano":"Pavlof","VolcanoID":"ak210","ParentVolcanoID":"ak210"},{"ID":525,"Name":"Great Sitkin 2001/2","Description":"   McGimsey and others (2004) report anomalous seismicity at Great Sitkin during 2001: \"Beginning in early February, 2001, seismicity at Great Sitkin volcano began to increase. The activity came to an abrupt end by the end of the month. The next seven months was characterized by short-lived seismic swarms that ended as quickly as they began, most only a day or two in duration. The largest swarm (15 events) occurred on Saturday, August 18, 2001.\"","StartYear":2001,"StartMonth":2,"StartDay":null,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2001,"EndMonth":9,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Great Sitkin","ParentVolcano":"Great Sitkin","VolcanoID":"ak111","ParentVolcanoID":"ak111"},{"ID":303,"Name":"Cleveland 2001/2","Description":"   From Dean and others (2002): \"Mt. Cleveland erupted explosively on 19 February and on 11 and 19 March 2001.  \r\n   * * * \"The first indication to AVO of activity at Mt. Cleveland was the 19 February eruption.  However, after the eruption, AVO received reports indicating that precursory activity had taken place.  Most graphic was a photograph taken on 2 February by a pilot flying by the volcano showing a dark, lobate deposit on the snow-covered southwest flank and robust steaming from the summit crater.  During this same period, residents of Nikolski observed steaming at the summit and snowmelt on the flanks of the cone.\r\n   \"On 19 February, Mt. Cleveland erupted explosively at approximately 1430 UT.  Pilot reports indicate that the altitude of the plume increased with time from 7.5 km a few hours after the start of the eruption, and up to 12 km eight hours later.  The eruption cloud and a thermal anomaly were detected on AVHRR satellite data at 1655 UTC.  The plume was complex and extended in two directions, 40 km northwest and 60 km southeast of the volcano. \r\n   * * * \"By 21 February (0300 UT), 35 hours after the eruption, the ash cloud was over 1000 km long and extended from Cook Inlet, Alaska, to Chukotsk Peninsula, Russia.  Eventually this long, arcing cloud split into three segments that drifted north over the Arctic Ocean, over Fairbanks near the center of the state, and south into the Gulf of Alaska.\r\n   * * * \"Mt. Cleveland erupted again on 11 March.  This explosive eruption lasted 3 hours (1400 to 1700 UT) based on satellite observations, with an estimated cloud height of 8 km.\r\n   * * * \"The 19 March eruption lasted up to 6 hours (2330-0530 UT), with an estimated cloud height of up to 9 km according to the National Weather Service.\r\n   * * * \"Throughout March and April, elevated surface temperatures and low altitude ash clouds were periodically observed on satellite data.  Ground and air observers noticed minor ash clouds over the volcano during the same period.\r\n   * * * \"Despite the extensive area traversed by the February plume, ash fall was observed only at Nikolski over a period of approximately 5 hours on 19 February.  Residents reported that the ash fall occurred under a hazy sky and consisted of a very light dusting of fine-grained material.  School children in Nikolski were given paper masks to wear home and residents were advised to stay indoors.  No injuries or health impacts have been reported; one resident noted that breathing outside without a mask 'made you want to cough.'\r\n   \"A sample from Nikolski shows that the ash is composed of glass shards, crystals, and lithics.  * * *  The glass is dacitic and has a magmatic morphology rather than phreatomagmatic.\"\r\n   Smith (2005), estimates a total erupted volume of deposits (not including tephra) from January through late March 2001 as 1.12 x10^6 cubic meters (+/- 3.07x10^5 cubic meters).","StartYear":2001,"StartMonth":2,"StartDay":2,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":"","EndYear":2001,"EndMonth":4,"EndDay":15,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":"","Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":178,"Name":"Okmok 2001/5","Description":"   McGimsey and others (2004) report on an earthquake swarm detected May 11, 2001, at Okmok Volcano: \"At 8:00 ADT (16:00 UTC) on the morning of May 11, 2001, AVO seismologists detected on the Makushin seismic network a swarm of earthquakes occurring under Okmok volcano prompting AVO to release an Update at 17:00 ADT (01:00 UTC). The events were ML=2.0-3.6 - too small to be felt by nearby residents - and determined to be possibly of volcanic origin. Satellite observations revealed no volcanic activity nor thermal anomalies. On-going satellite-based deformation measurements (SAR interferometry) show that the center of the caldera has inflated 20 cm between the 1997 eruption and September 2000. In April, 2001, AVO scientists observed an area of snowmelt in the caldera; although possibly indicative of heat flux, the area corresponded to the thickest part of the 1997 lava flow, which may still be hot (Patrick and others, 2003). By May 15, 2001, the earthquake swarm had greatly diminished. Okmok was last mentioned in the May 25, 2001 AVO Weekly Update.\"","StartYear":2001,"StartMonth":5,"StartDay":11,"StartTime":"08:00:00","StartQualifier":null,"StartQualifierUnit":"","EndYear":2001,"EndMonth":5,"EndDay":15,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":"","Volcano":"Okmok","ParentVolcano":"Okmok","VolcanoID":"ak206","ParentVolcanoID":"ak206"},{"ID":523,"Name":"Shishaldin 2001/6","Description":"   Shishaldin Volcano experienced some seismic unrest and a possible steam plume during 2001.  McGimsey and others (2004) report: \"AVO detected that seismic activity began increasing at Shishaldin Volcano in early June, 2001 and continued through about the end of November, 2001. On April 26, 2001, a pilot reported a steam cloud rising to about 2,000 ft. (~600 m) above the summit. Although the Color Code status of the volcano was never raised above 'GREEN', and the restlessness was not reported in any of our weekly updates, AVO seismologists and remote sensing specialists maintained a close watch on the activity.\"","StartYear":2001,"StartMonth":6,"StartDay":null,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2001,"EndMonth":11,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Shishaldin","ParentVolcano":"Shishaldin","VolcanoID":"ak252","ParentVolcanoID":"ak252"},{"ID":521,"Name":"Hague, Mt 2001/11","Description":"   McGimsey and others (2004) report that \"NWS observers in Cold Bay contacted AVO on the morning of November 7, 2001 to report a small steam plume originating from the south side of Pavlof; they also received several Pilot Weather Reports (PIREPS) describing the same observation. About a month later, on December 13, 2001, NWS personnel in Cold Bay reported steam issuing from a point about half-way down the south flank of the volcano. The plume rose to a height of about 6,000 ft (~1,830 m) before dissipating. A Pen Air pilot corroborated the report and added that the steaming was coming from a 'hill' on the southwest flank; this pilot added that he encountered a strong sulfur smell on a flight by the volcano that day. AVO detected no unusual seismicity or thermal anomalies. Based on conversations with the Pen Air pilot, AVO determined that the source of steaming was likely the fumarole field on nearby Mt. Hague, a late Pleistocene volcano with no historic activity.\"","StartYear":2001,"StartMonth":11,"StartDay":7,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2001,"EndMonth":12,"EndDay":13,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Hague, Mt","ParentVolcano":"Emmons Lake Volcanic Center","VolcanoID":"ak113","ParentVolcanoID":"ak93"},{"ID":529,"Name":"Hague, Mt 2002/2","Description":"   From Neal and others (2005): \"On February 15, 2002, AVO received a pilot report of steaming from the vicinity of Pavlof Volcano on the Alaska Peninsula.  AVO determined that the pilot had most likely spotted a steam plume from the summit crater of Hague, a youthful volcanic cone about 7 km (4 mi) southwest of Pavlof Volcano on the Alaska Peninsula.  The pilot reported that snow had melted in a crater at the site of this steaming, but the 'activity was not significant.'  AVO had received a similar report in mid-December, 2001 (steam was reported emanating from a 'hill' southwest of Pavlof, rising to about 6,000 ft [1,830 m] and dissipating, accompanied by a strong sulfur smell; McGimsey and others, 2005).  The Pavlof seismic network showed nothing unusual in conjuction with any of the reports, and no anomalies were observed in satellite images.\r\n   \"'Steaming' reports for the vicinity of Hague on the Alaska Peninsual continued into the spring.  In early April, AVO received email from a teacher in King Cove (35 km [20 mi]) south-southwest of Hague) describing 'steam from a large crater offset on the southwest side of Pavlof.'  Based on the position of the reported activity, it appears likely that the source was also a crater at the summit of Hague.  This same observer got a better look from the air on April 18 and confirmed that the crater was still steaming and releasing notable amounts of sulfur-bearing gas.  On May 1, USFWS personnel in Cold Bay shared photographs of steaming from the vicinity of Hague and noted that this was the first such observation in at least three years.\r\n   \"In mid-April, AVO seismologist examined records from the adjacent Pavlof Volcano network and noted that a family of shallow long-period events had been recorded in the general vicinity of Hague (J. Caplan-Auerback, written comm., 2002).  A second swarm of similar events occurred in May.  While the significance of this seismicity remains unclear, its coincidence in time with reports of increased steaming from the Hague crater does suggest a transient increase in heat flux and resulting hydrothermal activity.\"","StartYear":2002,"StartMonth":2,"StartDay":15,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2002,"EndMonth":5,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Hague, Mt","ParentVolcano":"Emmons Lake Volcanic Center","VolcanoID":"ak113","ParentVolcanoID":"ak93"},{"ID":530,"Name":"Shishaldin 2002/5","Description":"   From Neal and others (2005): \"In mid-May 2002, AVO detected an increase in the number of shallow, low-frequency seismic events at Shishaldin.  In addition, a number of 2-3 minute-long tremor-like signals were recorded.  No correlative thermal anomalies or other observations of unusual activity were reported to AVO.  AVO mentioned the activity in its weekly update of May 17.  On May 24, AVO reported in its weekly update that the numbers of locatable low-frequency seismic events had decreased to background levels.  Based upon this observation and the lack of correlative satellite-detected thermal anomalies or ground observer reports of anomalous activity, AVO concluded that the seismicity was probably typical of ongoing phreatic activity in the central crater and did not reflected significant restlessness.  AVO made no further mention of Shishaldin in May or June weekly updates.\r\n   \"On August 16, AVO received notification of a pilot report of possible volcanic activity at Shishaldin via the NWS Alaska Aviation Weather Unit (AAWU).  The pilot report indicated: 'Shishaldin Volcano appears to be erupting.  Steam and dark clouds rising to 10,500 [feet] moving NW-SE'.  During a follow up phone call to the area, AVO learned that a NWS weather observer in Cold Bay, about 100 km (60 miles) east of the volcano, reported a steam plume above Shishaldin.  According to operational protocols, the AAWU issued an eruption SIGMET advising the aviation community of the possibility of airborne volcanic ash.\r\n   \"Upon receiving the pilot report, AVO examined seismic and satellite data and determined that Shishaldin was at a normal background state and had not erupted.  Further discussions with the NWS weather observer in Cold Bay indicated that the observed steam plume was not unlike those commmonly seen at Shishaldin.\"","StartYear":2002,"StartMonth":5,"StartDay":15,"StartTime":null,"StartQualifier":7,"StartQualifierUnit":"Days","EndYear":2002,"EndMonth":8,"EndDay":16,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Shishaldin","ParentVolcano":"Shishaldin","VolcanoID":"ak252","ParentVolcanoID":"ak252"},{"ID":60,"Name":"Great Sitkin 2002/5","Description":"   This entry is not an eruption, but is a description of unusual earthquake activity at Great Sitkin that may be associated with volcanic events.\r\n\r\n   From 06/02 (BGVN 27:06) : \"Abnormal tremor and earthquake swarms in May 2002\r\nOn 27 and 28 May the Alaska Volcano Observatory (AVO) detected anomalous seismicity at Great Sitkin, a volcano located 1,895 km SW of Anchorage, Alaska. On 27 May two periods of seismic tremor lasted for 20 and 55 minutes and on 28 May earthquake swarms began at 0306 and 1228. The earthquake swarms each began with a relatively large event (ML 2.2 and ML 4.3) followed by tens to hundreds of smaller aftershocks, most located 5-6 km SE of the crater at depths of 0-5 km. Both the tremor and earthquake swarms represent significant changes from background seismicity at Great Sitkin. However, aftershocks declined significantly overnight, and seismicity returned to background levels with a lack of recorded tremor since 27 May. Satellite imagery showed no signs of surface volcanic activity, and no reports of anomalous activity were received by AVO.\"","StartYear":2002,"StartMonth":5,"StartDay":27,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":"","EndYear":2002,"EndMonth":5,"EndDay":28,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":"","Volcano":"Great Sitkin","ParentVolcano":"Great Sitkin","VolcanoID":"ak111","ParentVolcanoID":"ak111"},{"ID":526,"Name":"Wrangell 2002/8","Description":"   From Neal and others (2005): \"On August 1, 2002, a spectacular, clear day in south-central Alaska, AVO received several calls reporting an eruption of Mount Wrangell. Callers reported a dark cloud drifting downwind from the general summit area and a dark deposit high on the snow-covered flank of the volcano.\r\n   \"AVO seismologists checked data from the Wrangell seismic network and, based on a lack of correlative seismicity, concluded that no eruption or explosion had occurred. AVO also consulted with Wrangell St. Elias National Park Geologist Danny Rosenkrantz, who suggested that high winds had lofted fine-grained material exposed in the area near the summit fumaroles. On August 4, an AVO geologist traveling in the area verifed that a diffuse, light gray stripe extended a short distance down the flank of the volcano, emanating from the western rim of the caldera. \r\n   \"Subsequently, AVO received a video from Copper Center resident Brad Henspeter who witnessed the event on August 1. The tape is just a few minutes long and shows the waning portion of the event at approximately 1:15 pm ADT. In a written accompaniment to the videotape, Henspeter added his own commentary and recollections of the most significant portion of activity. Notable excerpts from his words follow: ‘..ash was dark black . . and billowing . . . multiple billows (puffing) coming one after the next, nearly touching each other. The wind where we were standing was still, however at the top of the mountain the wind was directly from the east . . .the billows were not rising above the top of the mountain.' By the time he and his son returned to a good vantage point to film, about 10-12 minutes later, the billowing had stopped and the 'puffs' had 'turned a more grayish color.' \r\n   \"In the video, there are indeed discrete, light gray 'puffs' that moved downwind and retained their individual.integrity. There are no other weather clouds in the vicinity. A.light gray, relatively motionless and irregular-shaped cloud sits in the vicinity of the caldera rim. There is a good breeze at ground level (indicated by motion in the trees) but at altitude, clouds are not shearing rapidly. High on the snow-covered flank, a gray-colored swath extends from a high point that we identify as the west caldera rim near Mount Wrangell Crater. The end of the video footage shows two distinct dark areas on the rim that is normally snow-covered. Henspeter's son reported a similar but more vigorous event on August 2, 2002 at about the same time of the day, but AVO received no further inquiries or reports. \r\n   \"AVO concluded that no volcanic process of significance was involved and no formal information releases were issued. However, these observations remain enigmatic: lack of any seismicity would seem to preclude a phreatic or magmatic eruption and yet the pulsatory, 'puffing' nature of the dirty clouds is difficult to reconcile with a wind phenomenon.\"","StartYear":2002,"StartMonth":8,"StartDay":1,"StartTime":"13:00:00","StartQualifier":30,"StartQualifierUnit":"Minutes","EndYear":2002,"EndMonth":8,"EndDay":2,"EndTime":"13:00:00","EndQualifier":2,"EndQualifierUnit":"Hours","Volcano":"Wrangell","ParentVolcano":"Wrangell","VolcanoID":"ak326","ParentVolcanoID":"ak326"},{"ID":324,"Name":"Veniaminof 2002/9","Description":"   From Neal and others (2005): \"On the basis of several days of increasingly frequent, emergent seismic events on multiple stations of the new Veniaminof network (Dixon and others, 2002), AVO announced Level of Concern Color Code YELLOW on September 11, 2002.  Following established protocols, the Anchorage Volcanic Ash Advisory Center (VAAC) issued a one-time volcanic ash advisory [see fig. 4 in original text].\r\n   \"Over subsequent weeks, seismicity was characterized by periods of above-background activity alternating with quiet intervals.  Telephone calls to Perryville and other nearby communities[see fig. 5 in original text] turned up no unequivocal observations of unrest until September 24 when AVO received phone reports and digital photographs from the Perryville Native Council.  These images showed small, faint gray clouds rising just above the intracaldera cone that has been the source of all known historical eruptions at Veniaminof (Miller and others, 1998).  One observer described 'puffs' of mixed dark and white clouds approximately every 5 minutes. Another observer described the 'puffs' as solid white and emanating from the top of the cone.\r\n   \"Perryville residents next reported 'plumes of smoke' between 8 and 10 pm on October 1. Others reported 'rumbling' during the evening, however no clearly correlative signals were noted on seismograms.  One and one half minutes of video taken on October 2 or 3, about 2 pm, from the vantage of the Sandy River (~45 km [28 mi] west of the active cone) showed several small, dilute, gray-brown clouds rising about 300-600 ft above the intracaldera cone and drifting a short distance to the north. In the 1.5 minutes of tape, two distinct 'puffs', about 1 minute apart, rise from the cone and drift downwind.  The cone was not unusually snow free, however, a dark covering of ash was visible on the caldera ice field at the base of the cone and extending generally north.  On October 6, Sandy River Lodge [see fig. 5 in original text] reported black ash and 'smoke' rising 400-500 ft above the cone, explosions, and ground shaking.  \r\n   \"Cloud-free satellite images of the Veniaminof caldera revealed nothing unusual until October 2 when AVO acquired a Moderate Resolution Imaging Spectroradiometer (MODIS) image that captured a localized, gray deposit on the caldera ice field [see fig. 6 in original text].  The image shows a faint, fan-shaped deposit extending generally east from the cone to the caldera boundary and perhaps just beyond.  When viewed in light of reports from Perryville and the video from Sandy River, the dark fan likely represents ash fall from low-level phreatic activity on October 1.  No thermal anomalies were detected in satellite imagery throughout this period and no incandescence was reported.  A compilation of reports from residents and other observers through the end of the year is presented in table 3.  Seismicity and reports of discolored clouds over the intracaldera cone gradually declined through the fall.\r\n   \"A re-invigorated hydrothermal system beneath the intracaldera cone may account for these intermittent ejections of diffuse, ash-bearing clouds. It seems unlikely that this was prompted by a new magmatic intrusion at depth based on the lack of volcano-tectonic earthquakes. Increased hydrothermal activity may have been related to what was, according to some long time residents of the area, one of the rainiest autumns in memory. Although precipitation falling at the elevation  of the intracaldera cone would have been in the form of snow (C. Searcy, NOAA, oral.commun., 2003), precipitation in Cold Bay [see fig. 1 in original text] was approximately 80% above normal for the month of October, according to long term climate records maintained by NWS (National Oceanic and Atmospheric Administration: http://www.arh.noaa.gov/climate.php). King.Salmon, the other nearby long-term weather station, recorded approximately 45% and 60% more precipitation than normal in the months of September and October, respectively.\"\r\n   The 2002 activity continued into 2003.  From McGimsey and others (2005): \"On January 3, 2003, AVO belatedly received a report from the caretaker of a lodge located northwest of the volcano describing his observations from about mid-December, 2002, during clear weather, of distinct puffs of steam coming from the intracaldera cone. AVO upgraded the Level of Concern Color Code to YELLOW on Monday, January 6, 2003. Several weeks of poor weather conditions followed before clear views revealed that intermittent episodes of steam and diffuse ash emissions from the active cone continued [see fig. 15 in original text]. AVO seismologists detected the onset of small, volcano-tectonic earthquakes on Veniaminof seismic stations beginning on the morning of January 29, 2003 and a commensurate decline in amplitudes and numbers of low-frequency events (S. Moran, written communication). Elevated seismicity continued, and on March 11, a 4-hour period of continuous seismic tremor was observed followed by 17 hours of discrete seismic events and 3-4-minute-long tremor bursts. This culminated with another 4-hour period of continuous tremor on March 12, which was followed by a distinct decline in seismicity over the next several days. The last report of emissions from the active cone was from Mark Battaion in Perryville on March 23, 2003 [see fig. 16 in original text].\r\n   From Neal and others (2005): \"In the summer of 2003, AVO geologists visited the summit caldera of Veniaminof and examined the intracaldera cone for evidence of the 2002 activity (K. Wallace, written.commun., 2003).  Within 50 m (160 ft) of the east side of the cone, the ice surface was dusted with fine wind blown debris derived from the cone. A crevasse at the base of the cone revealed a prominent, 1-cm-thick (0.4 in), black, scoriaceous deposit 1 m (3 ft) beneath the surface [see fig. 7a, b, in original text]. Scoria fragments ranged from fine ash to medium lapilli (with a maximum diameter of 5 mm [0.2 in]). The base of the crevasse was not visible, however no other debris layers were recognized over a thickness of at least 10 m (33 ft) suggesting that this type of depositional event was not common (e.g. wind reworking of cone debris).  In hand sample, the tephra consists of abundant black iridescent, glassy scoria; hydrothermally altered scoria (with native sulfur and secondary minerals); and rare individual crystals.  Microscopic investigation showed all glass fragments to be devitrified.  Wallace and co-workers concluded that this deposit represented recycled cone material ejected during low-level phreatic explosions in October 2002.\r\n   \"In response to the 2002 unrest at Veniaminof, AVO staff conducted outreach to communities in the vicinity of the volcano and compiled contact phone lists of observers and others who would be helpful in tracking activity on our behalf.  We were in frequent telephone contact with people in Perryville, regional airlines, and our colleagues at U.S. Fish and Wildlife Service (USFWS) and the Alaska State Troopers who were often flying in the area.  At least one private lodge near the volcano contacted AVO for information on potential hazards.  AVO posted a 'Frequently-Asked-Questions' about Veniaminof on our web site, a first in the history of AVO.\r\n   \"Interestingly, the change in Level of Concern Color Code to YELLOW for Veniaminof occurred on September 11, 2002, during a time when the Department of Homeland Security had recently established a Threat Level of ORANGE.  It is therefore possible that reaction to our initial information release on September 11 may have been more pronounced than usual, and confusion over the two color designations may explain why some residents of the Peninsula thought AVO had declared an 'imminent' eruption.\r\n   \"From September 11 to November 18, 2002, AVO issued three special information release notices on the increased seismicity and its eventual decline at Veniaminof.  The volcano was mentioned in weekly updates from September 13 through November 22.  AVO reverted to color code GREEN on November 18.  During the time of heightened activity, the AVO seismology and remote sensing groups increased the frequency of analysis of Veniaminof seismicity and relevant satellite imagery.\"","StartYear":2002,"StartMonth":9,"StartDay":28,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":"","EndYear":2003,"EndMonth":3,"EndDay":23,"EndTime":null,"EndQualifier":1,"EndQualifierUnit":"Months","Volcano":"Veniaminof","ParentVolcano":"Veniaminof","VolcanoID":"ak301","ParentVolcanoID":"ak301"},{"ID":541,"Name":"Mageik 2003/2","Description":"   From McGimsey and others (2005): \"AVO received a PIREP of steaming in the Katmai area -- specifically at coordinates 58\u0026deg;16', 154\u0026deg;50' -- that was rising to an estimated 17,000 ft. ASL on February 15, 2003. The AAWU called to consult as to whether or not to issue a Significant Meteorological Information Statement (SIGMET). A check of the webicorders and spectrograms revealed no unusual seismicity at any of the Katmai Group volcanoes and no advisory was forthcoming. Based on the coordinates reported and the past reports of steaming, the most likely source was Mageik [see fig. 9 in original text]. Nearby Martin also typically issues a vigorous steam plume.\r\n   \"An observer in the town of Naknek (about 110 km [70 mi.] from Mageik) called on April 8, 2003 to report two 'significant' steam plumes coming from 2 mountains in the VTTS the previous evening. Having lived in the area for 40 years, he stated that he had never seen anything as large as these plumes, although he estimated the plumes to be about 3,000 ft above the mountaintops.  AVO staff checked the webicorders and spectrograms of the greater Katmai network and found nothing out of the ordinary. The observer was advised that he was likely seeing vigorous steam plumes emanating from Martin and Mageik, a common occurrence in the Katmai area.\"","StartYear":2003,"StartMonth":2,"StartDay":15,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2003,"EndMonth":4,"EndDay":8,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Mageik","ParentVolcano":"Mageik","VolcanoID":"ak187","ParentVolcanoID":"ak187"},{"ID":537,"Name":"Wrangell 2003/6","Description":"   From McGimsey and others (2005): \"Danny Rosenkrans, geologist for the Wrangell-St. Elias National Park and Preserve, contacted AVO on June 13, 2003 with photographs taken by a local resident on June 11, 2003 showing an unusual, towering, cloud over the summit area of Mt. Wrangell (fig. 4). Although the cloud might simply have been a common cumulus cloud fortuitously located at or near the summit, the lack of other cumulus clouds in the area over nearby Mts. Drum and Sanford suggest that instead, calm weather conditions permitted steam emissions from the known summit fumaroles to coalesce and form the plume-like cloud over Wrangell. AVO receives several reports per year from pilots and local residents who observe what they consider to be larger than normal steam clouds situated over the summit.\"\r\n   \"On September 18, 2003 the Center Weather Service Unit (CWSU) called at 12:50 pm ADT with a Pilot Weather Report (PIREP) of a '2,000-to 2,300-foot-high steam plume' over Mt. Wrangell. The pilot reported no ash or sulfur smell. AVO scientists checked satellite imagery and seismograms and found nothing unusual.\"","StartYear":2003,"StartMonth":6,"StartDay":11,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2003,"EndMonth":9,"EndDay":18,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Wrangell","ParentVolcano":"Wrangell","VolcanoID":"ak326","ParentVolcanoID":"ak326"},{"ID":531,"Name":"Shishaldin 2004/2","Description":"   From Neal and others (2005): \"Since its last eruption in 1999, the background level of seismic activity at this frequently active volcano has remained relatively high and consists of many small, discrete, volcano-tectonic earthquakes, small explosion signals, and short (2-6 min) periods of tremor-like signals. Typically, this activity is interpreted to reflect either hydrothermal or magmatic processes occurring high in the conduit and deep in the summit crater of Shishaldin (Caplan-Auerbach and Petersen, 2005). Reports of ash emission or other eruptive phenomena that may have been related to this seismicity were few. However, on February 17, a Peninsula Airlines pilot noted a hazy ash layer above Shishaldin (R. Hazen, written commun., 2004). On February 20, a pilot report reached AVO describing an ash cloud to 16,000-18,000 ft ASL (4.8-5.5 km) above Shishaldin [note: AVO also received an incorrect pilot observation of ash from Mt. Dutton on February 20; this was later corrected to be Shishaldin.]. AVO seismologists identified no correlative seismicity or anything unusual on associated satellite images. NWS issued a one-time SIGMET based on the pilot report per operational protocols. A similar report from a long-time Cold Bay resident arrived via email on February 26 stating that Shishaldin was emitting steam and ash to 2,000-3,000 ft (600-900 m) above the summit; seismic and satellite data indicated no eruptive activity.\r\n   \"In late April and early May of 2004, seismicity at Shishaldin intensified and volcanic tremor similar to that observed during the eruption in 1999 reappeared. A thermal anomaly over the summit was noted on May 3 in MODIS imagery. Airwaves detected by acoustic pressure sensors suggested a shallowing of the source of this tremor over time (Petersen and others, 2004). In response, AVO raised the Level of Concern Color Code to YELLOW on May 3. On May 16, a pilot reported an ash plume rising 1,000 feet above the summit. Satellite data showed a vigorous steam plume possibly containing a minor amount of ash. Volcanic tremor and small explosions recorded on a pressure sensor continued into the summer and satellite images continued to record an intermittent, weak thermal anomaly into mid-August (S. Smith, written commun., 2005). On July 24, an AVO field crew approached the volcano by helicopter and observed vigorous steaming from the summit crater and recent (?) ash on the upper slopes of the volcano [See figures 18-20 in original text].\r\n   \"Low-level volcanic tremor continued at Shishaldin with little variation from late summer through the end of the year. AVO received at least two additional pilot reports of 'smoke' and 'steam' from Shishaldin, both on September 24. After more than five months at Color Code YELLOW, AVO downgraded Shishaldin to GREEN on October 26 based on the lack of any confirmed ash emission or other eruptive activity. Unlike most other Alaskan volcanoes, Shishaldin appears to have a high level of background seismicity, at least during the period following an eruption sequence (Caplan-Auerbach and Petersen, 2005; Nye and others 2002).\"","StartYear":2004,"StartMonth":2,"StartDay":17,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2004,"EndMonth":5,"EndDay":17,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Shishaldin","ParentVolcano":"Shishaldin","VolcanoID":"ak252","ParentVolcanoID":"ak252"},{"ID":325,"Name":"Veniaminof 2004/2","Description":"   From Neal and others (2005): \"In mid-February, residents of Perryville, located 35 km (22 mi) south of Veniaminof, reported small ash clouds rising several hundred feet above the intracaldera cinder cone of the volcano. At other times, vigorous, ash-free steam plumes were reported. On February 19, AVO received a pilot report of a small black ash cloud rising approximately 300 ft (90 m) above the cone and fresh ash on the snowfield east of the cone [see fig. 13 in original text]. A satellite image from the same day showed a dark deposit within the Veniaminof summit caldera. Seismic activity coincident with these reports was insignificant and AVO considered these small explosions to be typical of background activity at Veniaminof where ground water within the active cone occasionally flashes to steam producing a small explosion. The volcano had last produced such activity over a several month-period in late 2002 and early 2003 (Neal and others, 2005; McGimsey and others, 2005). On February 23, AVO described this activity in a special Information Release but remained at Level of Concern Color Code GREEN. AVO received no reports of activity over the next two weeks. Satellite imagery did not indicate increased surface temperatures or further ash deposits and seismicity remained low. AVO ceased special mention of Veniaminof in its weekly updates on March 5.\r\n   \"In mid-April, seismicity beneath Veniaminof began to increase and several episodes of volcanic tremor and isolated volcano-tectonic earthquakes were recorded. Tremor pulses were several minutes in duration and the largest were recorded on most stations in the network. On April 19, residents of Perryville reported a steam emission from the intracaldera cone that had occurred on April 18, possibly containing a small amount of ash. This burst rose an estimated 2,000 ft (610 m) above the intracaldera cone. Based on this renewed activity and elevated seismicity,  AVO elevated the Level of Concern Color Code for Mount Veniaminof to YELLOW. NWS issued a VAA and the FAA issued a temporary flight restriction from the surface to 14,000 ft ASL (4,270 m) within a 10 nautical mile (18.5 km) radius of the center of the volcano.\r\n   \"Over the next few weeks, Perryville residents reported vigorous steam plumes (often described as mushroom-shaped clouds) over the intracaldera cone. AVO received few reports of small ash emissions until April 25 when, using a newly installed remote video camera, as many as 25 small steam and ash emissions were observed over an 8-hour period, most rising about 2,000 ft (610 m) above the active cone [see fig. 14 in original text].\r\n   \"Through the remainder of spring and into summer, passing pilots, Perryville residents, personnel at Wildman Lake Lodge, and the AVO internet camera continued to record occasional steam plumes and steam and ash bursts, at times reaching as much as 915 m (3,000 ft) above the intracaldera cone and drifting as far as 16-32 km (10-20 mi). Poor weather obscured views of the volcano on many days, however bursts of tremor recorded on the seismic network likely reflected the continuation of small ash emissions, or 'puffs'. On May 5, a pilot spotted ash to 610 m (2,000 ft) above the cone and drifting east-southeast; on May 18, a pilot reported ash up to 3,000 ft (915 m) above the cone and drifting 32 km (20 mi) downwind. On May 26, satellite images of the volcano showed ash deposits on the north and southeast caldera floor.\r\n   \"Aerial views on June 27 revealed that much of the caldera floor was covered by a thin, dark layer of ash. On July 10, an AVO crew flying inside the caldera on a clear, calm day witnessed one of these ash bursts and captured it on video. As the helicopter approached the cone, only a faint wisp of steam and volcanic gas emerged from the summit of the intracaldera cone that consists of a series of coalescing craters each several 10s to 100 m wide. Suddenly, two closely spaced (20-30 seconds apart) vigorous explosions of gray-tan ash emerged from one of the central craters. The discrete puffs were followed by at least 2.5 minutes of continuous roiling of ash from the crater. Ash rose several hundred m (700-1,000 ft) above the cone and drifted downwind; ballistics and incandescence are not visible in this video clip. On July 22, an AVO field crew within the Veniaminof caldera witnessed another typical ash burst rising a few hundred ms (less than 1,000 ft) above the summit of the cone (fig. 15). Fallout was largely confined to the area around the base of the cone.\r\n   \"AVO geologists visited the ice field by helicopter in late July and reported a discontinuous, 1- to 2-mm thick ash blanket. They observed no large bombs or ballistics beyond the base of the cone, suggesting that recent ash emissions had not been accompanied by energetic explosions of large rock fragments. Further, they reported no changes in the ice field that would indicate subglacial melting. Additional observations of the cone were made in early August and photographs capture ash-poor puffs rising from one of several summit craters on the cone [see figs. 16, 17 in original text]. On August 7, geologists recorded 6-10 puffs over the course of about 10 minutes of focused observation. They reached about 150 m (500 ft) above the summit of the cone in fairly calm wind conditions.\r\n   \"Steam and ash emissions and correlative tremor bursts continued sporadically through the summer of 2004 but with decreasing frequency and intensity. Cloudy weather precluded any visual observations for much of September and October, however seismic signals continued to record small tremor bursts similar to those correlated with confirmed ash emissions earlier in the year. At times, only weak steaming was visible above the intracaldera cone. The last ash emission with localized ash fall was noted on the web camera images in early September. The pilot of a small aircraft reported 'light to moderate smoke' from Veniaminof on September 13. On October 26, AVO lowered the level of concern color code to GREEN based on a decline in the level of activity and an accompanying decrease in seismicity.\r\n   \"In response to the 2004 unrest at Veniaminof, AVO staff conducted outreach to communities in the vicinity of the volcano and revised existing contact phone lists of observers and others in the area. To track and document activity, a web-camera system was installed in Perryville in April (with assistance from the Perryville School and Perryville Village Council, gratefully acknowledged.) These images along with other graphical and text information were made available to the public via the AVO web site. AVO issued seven special Information Releases on the activity at Veniaminof.\"","StartYear":2004,"StartMonth":2,"StartDay":19,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":"","EndYear":2004,"EndMonth":9,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Veniaminof","ParentVolcano":"Veniaminof","VolcanoID":"ak301","ParentVolcanoID":"ak301"},{"ID":546,"Name":"Spurr 2004/7","Description":"   For a complete report of the unrest at Spurr between 2004 and 2006, please see Coombs and others (2006), available online at \u003ca target=\"_blank\" href =\"http://pubs.usgs.gov/pp/pp1732/pp1732b/index.html\" \u003e http://pubs.usgs.gov/pp/pp1732/pp1732b/index.html\u003c/a\u003e.\r\n   From Neal and others (2005): \"In early July 2004, AVO seismologists noted an increase in volcano-tectonic and long-period earthquake activity beneath the summit of Mount Spurr Volcano (Power, 2004; Power and others, 2004). About the same time, AVO was contacted by a long-time Alaskan pilot who flew near the volcano on July 11 and saw a small steam plume from the approximate 5,500 foot level of the east side of Crater Peak. She also reported an unusual sulfur dioxide odor. Based on this pilot report and the increase in seismicity, AVO launched a fixed-wing observation flight on July 15. Clouds prevented a view of the summit of Spurr, but Crater Peak and the lower south and east flanks of the Spurr summit dome were clear. Crater Peak appeared unchanged from previous views following the 1992 eruption and nothing unusual was noted along any of the glacier margins or termini around Crater Peak. The east flank of the Spurr summit dome, however, was marked by as many as a dozen dark debris flow lobes that emanated primarily from point-sources within the glacial cover [see fig. 5 in original text] (McGimsey and others, 2004).\r\n   \"Increased daily counts of shallow (5-10 km or 3-6 mi below sea level) earthquake activity combined with observations of debris flows from the summit prompted concern about the possibility of volcanic unrest at Spurr. On Monday July 26, AVO elevated the Level of Concern Color Code to YELLOW. A second AVO overflight on August 2 revealed a circular depression in the Spurr summit ice cap, approximately 50-60 m (165-200 ft) in diameter and 25 m (82 ft) deep [see figs. 6A and B in original text]. The pit contained an ice-encrusted pond with small areas of open water that were distinctly blue-gray in color [see fig. 6C in original text]. This feature became known as the 'ice-cauldron' following usage of the term at ice-covered Icelandic volcanoes.\r\n   \"From early August though early December, the summit ice-cauldron gradually enlarged as blocks of ice ringing the depression sagged and then collapsed into the pit [see figs. 6A, B in original text]. Careful measurements from images taken on August 10 and October 30 indicate that the pit enlarged from about 65 x 95 m (210 x 310 ft) across to 130 x 130 m (430 ft x 430 ft) across in two months' time (M. Coombs, written commun., 2004). Overflights throughout the late summer and fall documented the changing size of the feature, continuing deformation and collapse of surrounding ice walls, and the variability of open water on the surface of the lake. The lake remained a dark battleship gray color, and circular ice-free zones perhaps 5-10 m (16 x 33 ft) across occurred near bedrock lake shoreline and at several points further from the shore [see fig. 6C in original text]. By early December, the areas of exposed bedrock near the bottom of the cauldron had grown and were occasionally observed steaming. Yellow-tinted snow, ice, and rock outcrops in the vicinity of the lake reflected sulfur deposition near the lake margin.\r\n   \"AVO staff conducted several airborne Forward Looking Infrared Radiometer (FLIR) measurements using both a hand held and helicopter-mounted camera and video system. FLIR data confirmed the presence of at least two prominent areas of warm bedrock -- with temperatures as high as ~39o C or 102o F -- on the margins of the lake [see fig. 7A in original text] and on the outer flanks of the summit dome. Lake surface temperatures as measured by FLIR ranged from -10o to 0o C (14o to 32o F) for areas of floating ice and snow debris as well as open water [see fig. 7B in original text].\r\n   \"AVO also gathered an extensive library of satellite imagery of the Spurr edifice and increased satellite analysis frequency using the standard AVO monitoring imagery (Geostationary Operational Environmental Satellites [GOES], Advanced Very High Resolution Radiometer [AVHRR]) and higher resolution imagery (Advanced Spaceborne Thermal Emission and Reflection Radiometer [ASTER], Moderate Resolution Imaging Spectroradiometer [MODIS]). ASTER imagery showed the first signs of a summit thermal anomaly in nighttime thermal infrared data on August 17, 2004; as the summit lake grew in size, the intensity of the ASTER thermal infrared anomaly increased (R. Wessels, oral commun., 2005).\r\n   \"Five fixed-wing gas measurement flights of the Mount Spurr plume were conducted between early August and the end of October. Emission-rate measurements of SO2, H2S, and CO2 gas were made during each of these flights following protocols developed by the USGS (Gerlach and others, 1997; Gerlach and others, 1999; McGee and others, 2001 -- see original paper for complete references). Preliminary results show that CO2 degassing from the summit of Mount Spurr increased from 600 tonnes/day (t/d) in August to 1,300 t/d in September and finally to 1,400 t/d in October. At Crater Peak, CO2 emission rates were 160 t/d, 1,000 t/d and 120 t/d for the same measurement periods. Very small amounts of H2S (=3 t/d) were consistently measured on all of the flights at both degassing locations while no SO2 was detected at all.\r\n   \"Crater Peak has consistently degassed a small amount of CO2 since 1994 that, except for an anomalously higher value in 1997, is typically \u003c200 t/d (Doukas, 1995; M. Doukas, pers. commun., 2004). Carbon dioxide degassing from the summit of Mount Spurr had previously not been detected, although airborne measurements directed specifically at the summit have been rare. The absence of SO2 throughout this period is likely caused by the extremely wet environment at this glacier-clad volcano, where abundant groundwater dissolves SO2 (Doukas and Gerlach, 1995). This scrubbing process would also be greatly enhanced by the presence of the lake at the summit, and the distinctive battleship gray color of this lake might be partly due to dissolved sulfur compounds. The low but positive values for H2S can reflect the release of H2S from a boiling hydrothermal system (Symonds and others, 2001 -- see original text for full citation). This is consistent with historical reports of pressurized fumaroles described by climbers in the summit region and the presence of diffuse boiling-point fumaroles on outcrops of bedrock on the east side of the Mount Spurr summit dome (Turner and Wescott, 1986; C.J. Nye written commun., 2004).\r\n   \"Seismicity at Mount Spurr remained consistently above the pre-July 2004 background level for the remainder of the year, although daily rates of seismicity varied considerably from several to several tens of volcano-tectonic (VT) events per day. The largest tally of identifiable earthquakes in one day was 80 on October 26. Particularly energetic swarms of VT earthquakes located within 20 km (12 mi) of Mount Spurr occurred on October 26 (6.6 earthquakes per hour), November 4 (5.8 earthquakes per hour), August 14 (2.6 earthquakes per hour), and August 21 (1.8 earthquakes per hour). Throughout the unrest in 2004, VT seismicity was concentrated within 5 km (3 mi) of the Mount Spurr summit, in stark contrast to the pre-1992 seismicity (Power, 2004; Power and others, 2004). Located long-period (LP) events occurred at an average depth of approximately 7 km (4 mi) and at variable rates, peaking in November. Deep earthquakes (\u003e 20 km or 12 mi) were located beneath and south of Crater Peak in the same area as the deep seismicity associated with the end of the 1992 eruption of Crater Peak.\r\n   \"Although no eruptive activity ensued in 2004, AVO did experience an eruption response drill. A pilot report of possible ash from Mount Spurr on August 12, followed by a public ash fall advisory issued by the NWS, prompted a daylong flurry of calls, inquiries, and media attention. AVO issued a special Information Release stating that no eruption had occurred. This event— certainly not the first or last of its kind in AVO history—underscored the level of public concern regarding the situation at Mount Spurr and likely reflected a fresh memory of ash fall in 1992. The drill also facilitated review and improvement of communication protocols between AVO and its partner in ash warnings, the National Weather Service.\r\n   \"How unusual is this drastic change in the summit morphology at Mount Spurr? To our knowledge, this is the first documented episode of significant geothermal heating and generation of a substantial lake at the summit, as well as the first known occurrence of watery debris flows from the summit. Historical reports and aerial photographs from the 1950s, 60's and 70's, however, document significant variability in the snow and ice cover at the Mount Spurr summit. During periods of lower-snow levels, a crater-like structure becomes visible. This feature was described in March and others (1997) as a ~200 to 300 m (650-1,000 ft) diameter feature open to the east-northeast. In this same 1957 aerial photograph, a steep-walled, snow and ice pit, 20-30 m (65-100 ft) wide, is located in the ice cap near the base of the north summit crater wall. No open water can be seen in the bottom of the pit, however, several dark patches occur and could possibly represent warm bedrock.\r\n   \"AVO interprets this 2004 period of elevated seismicity and heat flux, summit melting, debris flow generation, and magmatic gas emission from both Spurr and Crater Peak to be the result of new injection of magma to a shallow level beneath the Spurr edifice (Power, 2004; Power and others, 2004). Magmatic gas flux from both Crater Peak and Mount Spurr suggests an open connection to the surface from the zone of intrusion or magma storage along two conduits. An alternative interpretation invokes release of volatiles from the still-cooling intrusions from the 1992 eruption series (Power and others, 1998; 2002).\r\n   \"Mount Spurr remained at Level of Concern Color Code YELLOW through the end of the year. Nearly all information release statements, weekly summaries, and daily status reports emphasized that despite the departure from background activity at Spurr, there were no signs of imminent eruptive activity. As part of this response, AVO mounted a number of observation flights, gas measurement and FLIR imaging flights, increased the frequency of satellite analysis, and installed six new seismometers and 3 permanent, continuous GPS receivers to improve seismic monitoring and track deformation of the volcanic edifice. On October 8, AVO announced the public availability of Internet web camera images of Mount Spurr on the AVO web site (http://www.avo.alaska.edu).\r\n   \"AVO issued three Information Releases on Mount Spurr activity in 2004 in addition to summarizing the Spurr situation in standard weekly updates on all Alaskan volcanoes. A number of articles appeared in the Anchorage Daily News (Anchorage Daily News 2004). In response to the YELLOW Level of Concern Color Code declaration, NWS issued a one-time Volcanic Ash Advisory (VAAS) and the FAA issued a Notice to Airmen (NOTAM) on July 26. The NOTAM was cancelled on November 9 (NOTAM 4/2284; B. Brown, FAA, pers. commun., 2005).\"\r\n   From McGimsey and others (2007): \"During 2005, elevated seismicity continued beneath Mt. Spurr, and the summit ice-collapse pit enlarged - becoming a large cauldron - as heat was supplied to the summit area.  The lake changed in size, and the amount of ice debris on the lake varied.  Lake level declined in May, seemingly associated with the generation of a small debris flow on the upper southeast flank.  With the decline in water level, subaqueous fumaroles emerged and the area of hot, steaming wall rock increased.  Temperatures of the warm zones measured with Forward-Looking Infrared Radiometer (FLIR) increased somewhat over the year.  Emissions of CO2 and SO2 decreased.  The Level of Concern Color Code for Mount Spurr remained at Yellow for all of 2005 (see table 6 in original text).\"\r\n   Neal and others (2009) report that the\"Level of Concern Color Code for Mount Spurr at the beginning of 2006 was YELLOW due to continued above-background seismicity, magmatic degassing, and the presence of an open, warm lake within a 300-m-diameter (980 ft) rock- and ice-walled cauldron atop the summit cone. Following months of no significant change in activity, AVO downgraded the Level of Concern from YELLOW to GREEN on February 21 [2006]. The information release cited a steady decrease in shallow seismicity between April and June 2005, after which earthquake activity remained slightly elevated above background levels through the remainder of 2005 and into 2006. By May 2006, seismicity at Mount Spurr ahd returned to background levels and remained there with few exceptions through the end of 2006. Intermittent observations permitted sporadic documentation of ongoing changes in the summit area as the geothermal activity continued to disrupt the ice field around the summit cone [see table 5 in original text].\"","StartYear":2004,"StartMonth":7,"StartDay":null,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2006,"EndMonth":2,"EndDay":null,"EndTime":null,"EndQualifier":2,"EndQualifierUnit":"Months","Volcano":"Spurr","ParentVolcano":"Spurr","VolcanoID":"ak260","ParentVolcanoID":"ak260"},{"ID":593,"Name":"Aniakchak 2004/12","Description":"   From McGimsey and others (2007): \"Beginning in mid-December 2004 and continuing into January 2005, several series of 10-20 low-frequency seismic events showed up on the Aniakchak seismic network.  On January 11, 2005, returning form an observation flight over nearby Veniaminof Volcano AVO staff photographed a partially ice-free Surprise Lake wihtin the Aniakchak caldera (see fig. 29 in original text).  A thermal anomaly of unknown source was detected in satellite data on February 1-3, 2005. Subsequent analysis and discussion among AVO scientists regarding these phenomena concluded that nothing unusual was likely occurring, and no further activity was noted in succeeding months.\"","StartYear":2004,"StartMonth":12,"StartDay":15,"StartTime":null,"StartQualifier":14,"StartQualifierUnit":"Days","EndYear":2005,"EndMonth":2,"EndDay":3,"EndTime":null,"EndQualifier":1,"EndQualifierUnit":"Months","Volcano":"Aniakchak","ParentVolcano":"Aniakchak","VolcanoID":"ak14","ParentVolcanoID":"ak14"},{"ID":4849,"Name":"Akutan non-eruptive activity 2005","Description":"From Cameron and others, 2023: \"In 2018, Akutan Volcano continued its long-term reinflation, which AVO has recorded since the installation of a GPS network at the volcano in 2005. The deformation was slightly faster in 2018 compared to its long-term rate. DeGrandpre and others (2017) noted that inflation at Akutan Volcano is episodic and suggested a shallow magma reservoir resides 6-10 km [3.7-6.2 mi] beneath the volcano. Continued inflation of the volcano is consistent with an ongoing accumulation of magma at shallow levels. The Aviation Color Code and Volcano Alert Level for the volcano remained at GREEN and NORMAL throughout 2018.\"\r\n\r\nFrom Orr and others, 2023: \"In prior years, activity at Akutan Volcano was characterized by a pattern of long-term reinflation, first observed after AVO field crews installed a Global Positioning System (GPS) network on the volcano in 2005. In 2019, however, the volcano deviated from this long-term trend by showing no systematic deformation that could be confidently linked to a volcanic source.\"","StartYear":2005,"StartMonth":1,"StartDay":1,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":"Years","EndYear":2019,"EndMonth":7,"EndDay":1,"EndTime":null,"EndQualifier":6,"EndQualifierUnit":"Months","Volcano":"Akutan","ParentVolcano":"Akutan","VolcanoID":"ak6","ParentVolcanoID":"ak6"},{"ID":533,"Name":"Veniaminof 2005/1","Description":"   From McGimsey and others (2007): \"After almost 4 quiet months, on January 4, 2005, AVO received a pilot report of small bursts of ash from the active cone rising a few hundred meters and drifting east, producing a narrow spoke-like deposit on snow within the caldera (see figs. 31 and 32 in original text).  This activity seemingly correlated with a period of continuous tremor recorded on the local seismic network that day, and a weak thermal anomaly was detected in an AVHRR satellite image.  AVO upgraded the Level of Concern Color Code for Veniaminof from Green to Yellow. AVO seismologists noticed that weak seismic tremor had begun on January 1 and increased over the subsequent week to levels last observed in May-June 2004.  Steam and ash emissions continued from the next several days and residents of Perryville, located 35 km (22 mi) south of Veniaminof, reported incandescence; the caretaker a ta local hunting lodge located west-southwest of the volcano reported seeing intermittent bursts of steam and ash.  Beginning on January 8, a persistent thermal anomaly began appearing in satellite images.  Then, on January 10, following nearly 48 hours of minor but nearly continuous ash emissions - some bursts reaching to 13,000 ft (3,692 m) above sea level - AVO raised the Level of Concern from Yellow to Orange.  The maximum amplitude of the seismicity had by then slightly exceeded that observed during the previous phase of unrest, which ended in September 2004.  AVO launched an overflight on January 11.  The crew observed nearly continuous low-level ash and steam emission from the central cone and much of the caldera was thinly covered in ash (see fig. 33 in original text).\r\n   \"Seismic data, web camera views, and satellite images indicated that low-level ash emissions continued for the next 5 weeks.  The seismicity was characterized by low-amplitude tremor with occasional larger bursts.  Weather permitting, satellite views showed anomalous heat at the summit cone consistent with hot blocks and ash ejection from the vent.  The web camera showed intermittent ash clouds with the highest reaching almost to 13,000 ft (4,000 m) ASL.  Strombolian eruptive activity was visible to the residents of Perryville during the night of February 3.  Then during the week of February 25, seismicity decreased substantially and only minor emissions of steam were observed.  AVO reduced the Level of Concern from Orange to Yellow.  By the end of the following week, volcanic tremor had subsided and seismic activity was deemed to be at background levels and the Level of Concern was reduced from Yellow to Green (see table 6 in original text).\r\n   Excerpts from AVO's information releases during this Veniaminof eruption are available online at: \u003ca href=\"http://www.avo.alaska.edu/archives/veniaminof2005/\"\u003ehttp://www.avo.alaska.edu/archives/veniaminof2005/\u003c/a\u003e\r\n   The Smithsonian Institution's Global Volcanism Bulletin (v. 30, n. 2) summarizes the event as follows: \"AVO raised the Concern Color Code at Veniaminof from Green to Yellow on 4 January because around that time several small ash emissions from the volcano's intracaldera cone were observed on the web camera in Perryville. Ash emissions were visible starting around 0938, but may have been obscured by meteorological clouds in previous images. The discrete ash emissions were small, rose hundreds of meters above the cone, and dissipated as they drifted E. Minor ash fall was probably confined to the summit caldera. Very weak seismic tremor was recorded beginning on 1 January, and increased slightly over the next 2 days. These seismic signals were similar to those recorded during steam-and-ash emissions in April to October 2004. However, there were no indications from seismic data that events significantly larger than those observed around 4 January were imminent.\r\n   \"AVO raised the Concern Color Code at Veniaminof from Yellow to Orange on 10 January as ash emissions from the volcano's intracaldera cone reached heights of nearly 4 km during 8-10 January [see figure 11 in original online source].  Seismicity remained at elevated levels and satellite images showed a persistent thermal anomaly at the intracaldera cone. On 11 January, the Anchorage VAAC again reported emission of a thin ash cloud to ~ 3 km altitude visible on the Perryville web camera. On 12 January the Anchorage VAAC reported emission of a thin ash cloud, visible on the Perryville web camera, that rose to 3-4 km altitude, extended ENE, and dissipated within ~ 55 km of the volcano. On 14 January, a satellite image showed a thermal anomaly in the vicinity of the Veniaminof summit. Although the anomaly appeared less intense than when first detected on 8 January and volcanism seemed to have declined significantly since 12 January, activity still remained significantly higher than normal with occasional bursts of volcanic tremor.\r\n   \"During the rest of the month of January, seismic data, web camera views, and satellite images indicated that low-level ash emissions continued at Veniaminof. Seismicity was similar to levels observed during the previous week, consisting of low-amplitude volcanic tremor with occasional larger bursts. During clear weather, satellite imagery showed anomalous heat at the summit cone, consistent with hot blocks and ash being ejected from the active vent. In addition, the web camera showed intermittent ash plumes reaching as high as 3 km altitude. Occasional stronger bursts of seismic tremor during 20-21 January and around 28 January may have indicated plumes to higher levels, but not above 4 km altitude. Veniaminof remained at Concern Color Code Orange.\r\n   \"Activity during February 2005. On the evening of 3 February, Strombolian activity at Veniaminof was visible by residents of Perryville ~ 30 km from the volcano. Activity was also observed on web camera views and seen by satellite as an increase in radiated surface heat. An increase in seismicity suggested that Strombolian activity may have continued through 4 February while the volcano was obscured by clouds.\r\n   \"During 28 January to 4 February, seismicity at Veniaminof was similar to levels for the previous week, with low-amplitude tremor and occasional larger bursts. During clear weather, satellite imagery showed anomalous heat at the summit cone, consistent with hot blocks and ash being ejected from the active vent. The web camera showed intermittent ash plumes reaching as high as 3 km altitude. Veniaminof remained at Concern Color Code Orange.\r\n   \"Low-level Strombolian eruptive activity continued at Veniaminof during 4-11 February. On 9 February, an ash burst rose hundreds of meters above the intracaldera cone. Satellite images continued to show a thermal anomaly in the vicinity of the intracaldera cone, consistent with the presence of hot material at the vent. Seismicity remained above background levels at the volcano. On the morning of 10 February there was a distinct increase in the amplitude and frequency of earthquakes. The increase continued through 11 February. This activity was consistent with more energetic explosions from the active cone, but there were no indications that the bursts rose higher than 4 km altitude. Veniaminof remained at Concern Color Code Orange.\r\n   \"During 11-18 February, it was likely that low-level Strombolian eruptive activity continued at Veniaminof based on seismic data and satellite imagery. Cloudy conditions obscured web camera views of the volcano, and no ash emissions were observed above the cloud cover. Seismicity remained above background levels at Veniaminof. The character of the seismicity changed slightly during the report period, with frequent periods of continuous banded volcanic tremor occurring, but the amplitudes of earthquakes did not increase. This activity was consistent with explosions from the active cone; however, there was no indication that these bursts rose more than 4 km altitude. Veniaminof remained at Concern Color Code Orange.\r\n   \"Seismicity decreased substantially at Veniaminof during 18-25 February in comparison to previous weeks, leading AVO to decrease the Concern Color Code from Orange to Yellow. Periods of volcanic tremor diminished, and no discrete events associated with ash bursts had occurred for several days. Only minor steam emissions were seen. AVO received no reports of ash emissions from pilots or ground observers. AVO concluded that given the decline in seismicity, it appeared that the most recent episode of Strombolian eruptive activity at Veniaminof had ended.\r\n   \"Activity during March 2005. A further reduction in activity at Veniaminof during 25 February to 4 March led AVO to reduce the Concern Color Code from Yellow to Green, the lowest level. For more than a week seismic activity was at background levels, periods of volcanic tremor had ceased, and there were no discrete events associated with ash bursts. Only minor emissions of steam were observed on the web camera and satellite imagery. AVO received no reports of ash emissions from pilots or observers on the ground. They concluded that given the decline in seismicity it appeared that the most recent episode of eruptive activity had ended at Veniaminof.\"","StartYear":2005,"StartMonth":1,"StartDay":4,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2005,"EndMonth":2,"EndDay":25,"EndTime":null,"EndQualifier":7,"EndQualifierUnit":"Days","Volcano":"Veniaminof","ParentVolcano":"Veniaminof","VolcanoID":"ak301","ParentVolcanoID":"ak301"},{"ID":532,"Name":"Korovin 2005/2","Description":"   From McGimsey and others (2007): \"On the morning of February 24, 2005, AVO received a report from residents of Atka Village that Korovin had erupted the previous evening, producing a large steam and ash cloud.  February 23 was a clear day and local residents had noticed minor steaming from Korovin about noon (see fig. 40 in original text).  Then, about 7 p.m. HST (8 p.m. AST), they witnessed a dark plume over Korovin, rising several thousand feet high, drifting east, that had ash visibly falling out near the base, presumably confined to the flanks of Korovin (see fig. 41 in original text).  Several minutes later, three or four smaller, gray puffs occurred. Although they watched, no further activity ensued during the calm, clear, moonlit night.\r\n   \"Satellite data from about the time of the reported activity indicated the presence of a 1-2 pixel thermal anomaly and a small steam plume, possibly with localized minor ash.  Height of the steam plume was estimated to be about 10,000 ft (~3 km), corroborating the observer account.  AVO issued an Information Release on February 24 and raised the Level of Concern Color Code to Yellow.  With no further reports of continuing activity, nothing evident in subsequent satellite data, and no unusual seismicity from a seismic station in Atka Village, AVO reduced the Color Code from Yellow to UA in the March 4, 2005, Weekly Update (see table 6 in original text).  Evidence of similar activity has been identified in 2002 and 2004 satellite images and observed by field crews in 2004 (see fig. 42 in original text).\r\n   \"A PIREP of steam reaching several thousand feet above Korovin on March 19 was the next report of activity, and then in early May observational data indicated that the lake had drained in the south summit crater of Korovin and that incandescence was visible in the about 100-m (~325 ft) - wide pit.  The next several months were quiet.","StartYear":2005,"StartMonth":2,"StartDay":23,"StartTime":"19:00:00","StartQualifier":null,"StartQualifierUnit":null,"EndYear":2005,"EndMonth":5,"EndDay":7,"EndTime":null,"EndQualifier":14,"EndQualifierUnit":"Days","Volcano":"Korovin","ParentVolcano":"Atka volcanic complex","VolcanoID":"ak171","ParentVolcanoID":"ak17"},{"ID":601,"Name":"Martin 2005/2","Description":"   From McGimsey and others (2007): \"On February 26 [2005], AVO received from the Center Weather Service Unit (CWSU) several pilot reports of a steam cloud rising to 12,000 ft (3,360 m) from Katmai.  An inspection of the webicorders, spectrograms, and satellite logs revealed nothing unusual.  Because Katmai Volcano does not have active fumaroles, the reported activity was attributed to nearby Mounts Mageik or Martin, both of which have active fumaroles that frequently produce noticeable steam plumes.  Nonvolcanic meterological phenomena that commonly are mistaken for volcanic activity also are common in this area.\"","StartYear":2005,"StartMonth":2,"StartDay":26,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2005,"EndMonth":2,"EndDay":26,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Martin","ParentVolcano":"Martin","VolcanoID":"ak189","ParentVolcanoID":"ak189"},{"ID":602,"Name":"Mageik 2005/2","Description":"   From McGimsey and others (2007): \"On February 26 [2005], AVO received from the Center Weather Service Unit (CWSU) several pilot reports of a steam cloud rising to 12,000 ft (3,360 m) from Katmai.  An inspection of the webicorders, spectrograms, and satellite logs revealed nothing unusual.  Because Katmai Volcano does not have active fumaroles, the reported activity was attributed to nearby Mounts Mageik or Martin, both of which have active fumaroles that frequently produce noticeable steam plumes.  Nonvolcanic meterological phenomena that commonly are mistaken for volcanic activity also are common in this area.\"","StartYear":2005,"StartMonth":2,"StartDay":26,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2005,"EndMonth":2,"EndDay":26,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Mageik","ParentVolcano":"Mageik","VolcanoID":"ak187","ParentVolcanoID":"ak187"},{"ID":595,"Name":"Pavlof 2005/4","Description":"   In April and May, 2005, fumarolic activity at nearby Mount Hague was erroneously reported as plumes emanating from Pavlof.  See \u003ca href=\"http://www.avo.alaska.edu/volcanoes/volcact.php?volcname=Emmons%20Lake%20Volcanic%20Center\u0026eruptionid=594\u0026page=basics\"\u003ehttp://www.avo.alaska.edu/volcanoes/volcact.php?volcname=Emmons%20Lake%20Volcanic%20Center\u0026eruptionid=594\u0026page=basics\u003c/a\u003e for more information.","StartYear":2005,"StartMonth":4,"StartDay":16,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2005,"EndMonth":5,"EndDay":24,"EndTime":null,"EndQualifier":7,"EndQualifierUnit":"Days","Volcano":"Pavlof","ParentVolcano":"Pavlof","VolcanoID":"ak210","ParentVolcanoID":"ak210"},{"ID":594,"Name":"Hague, Mt 2005/4","Description":"   From McGimsey and others (2007): \"National Weather Service personnel in Cold Bay reported a steam plume emanating from the side of Pavlof on April 16, 2005.  Subsequent analysis of the photographs sent to AVO indicated that the steam cloud originated instead from adjacent Mount Hague (see fig. 35 in original text), possibly from the fumarolic field located on the south flank - instead of the crater lake - based on the plume position; however, no direct observations confirmed the source.  Seismicity was determined to be normal.\r\n   \"On May 23 and 24, 2005, observations of steam - this time possibly containing some ash - rising to as much as 3,000 ft (~900 m) above Pavlof were again reported to AVO, as well as to FAA and AAWU.  Photographs revealed that the plume originated instead from Mount Hague (see fig. 36 in original text).  Analysis of satellite images revealed no evidence of ash, and no unusual seismicity was recorded.  One of the two summit craters on Mount Hague contains vigorous fumaroles and has produced strong steam emissions in previous years (see table 7 in original text).  The activity was interpreted to result from normal fluctuation of the hydrothermal system at Mount Hague and was reported in the AVO Weekly Update on May 27, 2005.\"","StartYear":2005,"StartMonth":4,"StartDay":16,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2005,"EndMonth":5,"EndDay":24,"EndTime":null,"EndQualifier":7,"EndQualifierUnit":"Days","Volcano":"Hague, Mt","ParentVolcano":"Emmons Lake Volcanic Center","VolcanoID":"ak113","ParentVolcanoID":"ak93"},{"ID":536,"Name":"Cleveland 2005/4","Description":"   From McGimsey and others (2007): \"After several years of quiescence following an explosive eruption in 2001, AVO remote sensors observed a 3-pixel thermal anomaly at the summit of Cleveland on March 13, 2005 (see fig. 38 in original text).  On April 27, 2005, the FAA alerted AVO of a pilot report of eruptive activity - \"ash cloud * * * 15,000 to 18,000 ft high\" - in the vicinity of Cleveland (based on coordinates from the pilots).  Satellite images showed no evidence of activity.  AVO seismologists checked seismic data from the nearest stations (Nikolski, located 75 km [45 mi] east, and at Okmok Volcano, 150 km [93 mi} east of Cleveland), and found nothing unusual.  CWSU issued a one-time Urgent Pilot Report, and AAWU issued a one-time SIGMET.  Although time-series thermal data did not record any evidence of activity, short-lived minor explosive activity would not be considered unusual for Cleveland and could go undetected if it occurred during periods between acquisitions of satellite images or if concealed within the frequent cloud cover.\r\n   \"Following the detection of a 1-pixel thermal anomaly at the summit on June 28, evaluation of before and after satellite images suggested the presence of a lahar deposit on the northeast flank, inferring that minor activity persisted at Cleveland.  Then, on July 5, the entire upper flanks of the volcano were observed dusted with ash in a satellite image (see fig. 39 in original text).  AVO rasied the Level of Concern Color Code from Unassigned (UA) to Yellow in an Information Release on July 7, 2005 (see table 6 in original text).  The presence of ash, minor blocky avalanche-like deposits, and thermal anomalies was consistent with low-level Strombolian eruptive activity (D. Schneider, AVO logs). \r\n   \"Thereafter, although a thermal anomaly was observed on August 11, the activity appeared to wane.  AVO reduced the Color Code from Yellow back to UA on August 27.  But the volcano remained restless, and a summit thermal anomaly again was observed on August 31.  By mid-September, AVO was ready to test a new automated system that detects thermal anomalies and raises an alert.  On September 21, this new system successfully detected a thermal anomaly at the summit of Cleveland.  For the next few weeks, the volcano remained quiet.  Then, on the morning of October 7, AVO detected in satellite images a small drifting ash cloud located about 150 km (90 mi) east-southeast of Dutch Harbor.  On the basis of regional seismic data at Nikolski (75 km [45 mi] east of the volcano), and backtracking the ash cloud, AVO concluded that a small eruption had occurred at Cleveland at approximately 01:45 ADT (0945 UTC).  AVO and the NWS worked together to determine that the ash cloud was at an altitude of no more than 15,000 ft (4,600 m).  No ash fell in Nikolski.  AVO immediately raised the Color Code from UA to Orange and NWS issued a SIGMET indicating that the ash cloud was moving east.  The next day, October 8, ther was no sign of ash emission or a summit thermal anomaly, and on October 10 the Color Code was downgraded from Orange to Yellow.  The last thermal anomaly was seen on November 6, and steam plumes were occasionally visible in satellite data for the next several weeks.  Because there was no evidence of ash emissions on November 25, AVO reduced the Color Code for Cleveland from Yellow to UA.  As fate would have it, a few days later, evidence for minor eruptive activity was observed; however, the activity did not continue and the volcano remained quiet for the rest of the year.  AVO issued five special Information Releases about Cleveland activity between July 7 and November 25, 2005.\"\r\n    A chronology of this event is available at: \u003ca href=\"http://www.avo.alaska.edu/archives/Cleveland2005.php\"\u003ehttp://www.avo.alaska.edu/archives/Cleveland2005.php\u003c/a\u003e\r\n   From the Smithsonian Institution (2005): \"Mount Cleveland produced significant ash plumes during March 2001 (BGVN 26:04). Volcanic unrest continued through 4 May 2001, and signals consistent with volcanic seismicity were detected by an Alaska Volcano Observatory (AVO) seismic network 230 km E. By the end of May, neither eruptive activity nor thermal anomalies were observed. Until July 2005, no alert level was assigned, and AVO monitoring produced no reports on Cleveland.\r\n   \"Cleveland lacks a real-time seismic network. Accordingly, even during times of perceived quiet there is an absence of definitive information that activity level is at background. AVO's policy for volcanoes without seismic networks is to not get assigned a color code of Green.\r\n   \"Satellite imagery of Cleveland taken during 24 June to 1 July 2005 showed increased heat flow from the volcano and a possible debris flow. AVO stated that although observations were inhibited by cloudy weather, they indicated the possibility of increased volcanic activity. AVO did not assign a Concern Color Code to Cleveland due to the lack of seismic monitoring and limited satellite observations.\r\n   \"Satellite images during 1-8 July showed increased heat flow, thin ash deposits, and possible debris flows extending ~ 1 km down the flanks from the summit crater. AVO assigned a Concern Color Code of Yellow on 7 July. On 18 July satellite imagery showed steam emanating from Cleveland's summit and evidence of minor ash emissions. Meteorological clouds obscured Cleveland during the third week of July. During 22-29 July satellite images showed minor steaming from the summit, possible fresh localized ash deposits, and a weak thermal anomaly.\r\n   \"On 4 August satellite images showed a thermal anomaly. On 27 August AVO reduced the Concern Color Code at Cleveland from Yellow to \"Not Assigned\" because there had been no evidence of activity since a thermal feature was observed on satellite imagery from 11 August. A thermal feature was detected on several satellite images obtained on 31 August, and one on 19 September, but there was no evidence of eruptive activity.\r\n   \"On 7 October, AVO raised the Concern Color Code to Orange after detecting a small drifting volcanic ash cloud. The cloud was seen in satellite data at a spot ~ 150 km ESE of Dutch Harbor at 1700 UTC. Based on data from a regional seismometer at Nikolski, AVO concluded that the ash came from a small Cleveland eruption at approximately 0145. AVO, in consultation with the National Weather Service, estimated the top of the ash cloud to be no more than 4,600 m altitude. The ash cloud dissipated and was not detected via satellite after 1800 UTC. Three days passed during which there were no new observations of eruptive activity at Cleveland from satellite data, pilots, or ground-based observers. Accordingly, on 10 October the Concern Color Code was reduced to Yellow.\"","StartYear":2005,"StartMonth":4,"StartDay":27,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2005,"EndMonth":9,"EndDay":27,"EndTime":null,"EndQualifier":3,"EndQualifierUnit":"Months","Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":592,"Name":"Iliamna 2005/5","Description":"   From McGimsey and others (2007): \"On May 15, 2005, AVO seismologists noted a swarm of unusual seismic activity at Iliamna.  The events were emergent and prolonged (longest lasted 5-8 minutes), and were strongest at seismic station ILS, located on the south flank of South Twin (see fig. 14 in original text).  The activity began about 1250 UTC and tapered off at 1718 UTC.  Analysis revealed that the signals most likely were caused by a surficial process, such as a snow avalanche - a common occurrence on Iliamna - but this particular event lacked the usual precursory seismicity preceding other Iliamna snow and ice avalanches (J. Caplan-Auerbach and others, 2004; J. Caplan-Auerbach, written commun., 2005; Caplan-Auerbach and Huggel, 2007.)  Corroborating evidence arrived on the morning of May 17 when Lee Fink of Lake Clark National Park called AVO to offer his observations from an overflight of the area the previous day.  Fink reported seeing a large, fresh rock slide (not a snow or ice avalanche) southeast of Iliamna that began about the 6,500-ft level on the southeast flank of South Twin and ran down to about the 1,200-ft elevation (see fig. 15 in original text).  The lengthy ridge extending south of Iliamna that includes South and North Twins and a large unnamed massif has steep, exposed sections of bedrock that frequently generate rock falls, and occasionally large rockslides, such as occurred on May 15 at South Twin.\"","StartYear":2005,"StartMonth":5,"StartDay":15,"StartTime":"00:50:00","StartQualifier":null,"StartQualifierUnit":null,"EndYear":2005,"EndMonth":5,"EndDay":15,"EndTime":"17:18:00","EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Iliamna","ParentVolcano":"Iliamna","VolcanoID":"ak124","ParentVolcanoID":"ak124"},{"ID":598,"Name":"Kasatochi 2005/7","Description":"   From McGimsey and others (2007): \"In late July 2005, AVO was contacted by Vern Byrd of U.S. Fish and Wildlife Service (USFWS)/Homer who passed along a report from a USFWS field camp on Kasatochi Island, located about 50 km (~30 mi) east of Great Sitkin and about 100 km (~60 mi) west of Korovin Volcano.  On June 23, members of the field party viewed the lake and noticed nothing unusual.  Then, on July 27, the same field party peered into the summit crater from the rim and saw the lake 'simmering, not quite a roiling boil, concentrated in a few patchy areas, bubbling more violently in the western half of the lake, * * * lake appeared thin (sic), no steam observed at all.'  The bubbling areas were intermittent.  The observers did not feel vibrations or earthquakes or hear anything odd, nore did they detect unusual odors or water discoloration (the lake typically is turbid and turquoise in color).  Gulls landed unperturbed on the water surface.  The observers concluded that what they were seeing was a distinct change from the previous month and from conditions present during the past several years on the island.\r\n   \"Biologists visited the crater rim again on August 1 and reported no significant change from the activity reported on July 27.  They mentioned that the lake was perhaps 'simmering a little less with less area of the lake affected.'  A check of satellite imagery for any sign of thermal anomaly or other change during this time period came up negative, however, clear views of this frequently cloud-covered small island were few (ASTER, Landsat, R. Wessels, USGS/AVO, oral commun., 2005).\r\n   \"A USGS-contracted helicopter in Adak transported an AVO geologist and the USFWS field party chief Brie Drummond to Kasatochi on September 2 to investigate.  Winds were high and fog and clouds intermittently obscured the summit crater rim.  During one low pass over the lake, no signs of bubbling or upwelling were observed.  Two patches of brown scum 2-3 m (6.5-10 ft) across floated in the approximate area where bubbling was observed earlier in the summer (see fig. 44 in original text).  No signs of recent lake level disturbance or hydrothermal activity were noted.\"","StartYear":2005,"StartMonth":7,"StartDay":27,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2005,"EndMonth":9,"EndDay":null,"EndTime":null,"EndQualifier":28,"EndQualifierUnit":"Days","Volcano":"Kasatochi","ParentVolcano":"Kasatochi","VolcanoID":"ak146","ParentVolcanoID":"ak146"},{"ID":534,"Name":"Veniaminof 2005/9","Description":"   From McGimsey and others (2007): \"Veniaminof remained relatively quiet [since February, 2005] until early September when several minor bursts of ash were observed by Perryville residents and visible on the web camera (see fig. 34 in original text).  This and an increase in seismicity prompted AVO to elevate the Level of Concern from Green to Yellow on September 7.  The minor unrest continued only for a couple of weeks when seismicity once again decreased to background level and there were no observations of emissions.  AVO reduced the Level of Concern from Yellow to Green on September 28.\r\n  \"Then, on November 4, a low-level, minor ash emission visible in the webcam prompted AVO to raise the Level of Concern from Green to Yellow.  Slightly elevated seismicity persisted for the next few weeks but poor weather conditions precluded visual observations.  By mid-December, seismic levels were again down to background level, and on December 30, the Level of Concern was downgraded from Yellow to Green, the 8th Color Code change of the year for Veniaminof (see table 6 in original text).\"\r\n   From the Smithsonian Institution (2006, v. 31, n. 3): \"On 7 September 2005, the Alaska Volcano Observatory (AVO) noted several minor bursts of ash from the volcano during the afternoon. Ash bursts continued to occur through at least 9 September, with ash rising less than 3 km altitude, and with the ash confined to the caldera. Over the following 2 weeks, minor ash emission continued at a rate of 1-5 events per day based on interpretations of seismic data. AVO reported that it was likely that diffuse ash plumes rose to heights less than ~ 3 km and were confined to the summit caldera. Cloudy weather during 16-23 September prohibited web-camera and satellite observations of Veniaminof, but seismic data indicated diminishing activity. On 28 September seismicity had remained at background levels for over a week, and there was no evidence to suggest that minor ash explosions were continuing.\r\n   \"On 4 November 2005, a low-level minor ash emission occurred from the intracaldera cone beginning at 0929. Ash rose a few hundred meters above the cone, drifted E, and dissipated rapidly. Minor ashfall was probably confined to the summit caldera. During the previous 2 weeks, occasional steaming from the intracaldera cone was observed. Very weak seismic tremor and a few small discrete seismic events were recorded at the station closest to the active cone. However, AVO reported that there were no indications from seismic data that a significantly larger eruption was imminent.\"\r\n   Execerpts from AVO's weekly updates and information releases for this time period can be found at this website: \u003ca href=\"http://www.avo.alaska.edu/archives/Veniaminof_2005_09.php\"\u003ehttp://www.avo.alaska.edu/archives/Veniaminof_2005_09.php\u003c/a\u003e.","StartYear":2005,"StartMonth":9,"StartDay":7,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2005,"EndMonth":11,"EndDay":4,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Veniaminof","ParentVolcano":"Veniaminof","VolcanoID":"ak301","ParentVolcanoID":"ak301"},{"ID":597,"Name":"Korovin 2005/9","Description":"   From McGimsey and others (2008): \"On September 13, 2005, a long sequence of strong seismicity was recorded on the newly operational Korovin seismic network.  The sequence began with two small local events followed by about 30 minutes of weak tremor, and then about 20 weak local events.  Nothing unusual was detected on satellite images of the time period.\r\n   \"Although a network of seismic stations was installed on northern Atka Island during the summer of 2004, data were not accessible until early March 2005, and Korovin was not considered to be seismically monitored until late 2005 - announced in the December 2, 2005, Information Release - when a sufficient period of background seismicity had been recorded, and equipment/communications problems resolved (see table 1 in original text).  On December 2, Korovin, which previously had been listed as UA, was formally assigned Color Code Green.\"","StartYear":2005,"StartMonth":9,"StartDay":13,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2005,"EndMonth":9,"EndDay":13,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Korovin","ParentVolcano":"Atka volcanic complex","VolcanoID":"ak171","ParentVolcanoID":"ak17"},{"ID":599,"Name":"Tanaga 2005/10","Description":"   From McGimsey and others (2007): \"Earthquake activity at Tanaga increased abruptly on October 1, 2005.  Over the next several days, the number of located events ranged from 15 to 68 per day, in striking contrast to the typical one earthquake per month previously recorded since the seismic network was installed in 2003.  The earthquakes centered a few kilometers northeast of the summit of Tanaga at a depth of 10-20 km (~6-12 mi), and the largest event had a magnitude of 1.7.  AVO issued a special Information Release on October 5 to announce the activity.  The activity further escalated that day and again early on October 7 with located earthquakes of magnitude 0.5-1.9 shallowing to depths of 6-12 km (~4-7.5 mi) beneath Tanaga's summit.  This change in activity prompted AVO to raise the Level of Concern Color Code from Green to Yellow on October 7, 2005.  By the following week, the daily earthquake count had fallen slightly, and by the next week, earthquake activity had diminished further, but remained above background levels.  A several-minute-long period of unusual seismicity occurred on October 17 and may have been a landslide or small phreatic explosion, but no signs of activity were visible in satellite images.  Although the daily earthquake count continued to dwindle, nearly continuous, weak volcanic tremor was recorded on seismic stations closest to nearby Takawangha Volcano on October 24 (see fig. 47 in original text).  This was the first episode of tremor recorded at the Tanaga cluster since the seismic network was installed in 2003.  Weak tremor continued for the next several weeks, gradually declining.  Seismicity continued to decline further during November, and by the end of the month the likelihood of an eruption was considered significantly decreased.  In an Information Release issued on November 25, 2005, AVO reduced the Level of Concern Color Code from Yellow to Green.\"","StartYear":2005,"StartMonth":10,"StartDay":1,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2005,"EndMonth":11,"EndDay":null,"EndTime":null,"EndQualifier":14,"EndQualifierUnit":"Days","Volcano":"Tanaga","ParentVolcano":"Tanaga","VolcanoID":"ak280","ParentVolcanoID":"ak280"},{"ID":547,"Name":"Augustine 2005/12","Description":"   From Power and others (2006): The 2006 eruption of Augustine consisted of four phases defined by the character of unrest or eruptive activity, which are described below. These phases are the precursory (May 2005 to 11 January 2006), the explosive (11 to 28 January), the continuous (28 January to 2 February), and the effusive (2 February to late March).\r\n   \"The precursory phase began as a steady increase in microearthquakes beneath the volcano, ranging from one to two per day in May 2005 to 15 per day in mid-December [see Figure 3 in original text]. In July 2005, geodetic baselines began to lengthen, indicative of pressurization at sea level centered beneath the edifice (Cervelli and others, 2006). On 2 December 2005, seismometers began recording signals from small phreatic explosions; the largest signals occurred on 10, 12, and 15 December. An overflight on 12 December revealed vigorous steaming, a new vent on the summit's southeastern side, and a dusting of ash on the volcano's southern flanks. The ash was a mix of weathered and glassy particles; the latter appear to be remobilized 1986 tephra. An explosion on 15 December disabled the telemetery for the two highest seismic stations [see figure 2 in original text].\r\n   \"Augustine then entered an explosive phase, which lasted from 11-28 January 2006. A strong swarm of volcano-tectonic (VT) earthquakes began at 0030 UTC on 11 January, culminating in explosive eruptions at 1344 and 1412 UTC. These explosions produced ash plumes, reported by the U.S. National Weather Service (NWS) to have reached heights greater than nine kilometers above sea level (asl), which moved slowly to the north and northeast. Ash sampled on 12 January was primarily dense or weathered fragments, suggesting little juvenile magma. Over the next 36 hours, several sequences of small, regularly spaced VT earthquakes, many with identical waveforms, occurred at rates as high as three to four per minute. Similar earthquakes, referred to as clones or drumbeats, have been associated at other volcanoes with the emplacement of lava domes (Dzurisin and others, 2005).\r\n   \"Monitoring instruments also recorded six powerful explosions that occurred between 1324 UTC on 13 January and 0914 UTC on 14 January [see figure 3 in original text]. The first explosion destroyed the seismometer and CGPS high on the volcano's northeastern flank [see figure 2 in original text]. Plumes reached altitudes of 14 kilometers asl and deposited traces of ash on southern Kenai Peninsula communities. Ash from these eruptions was more heterogeneous and contained dense particles as well as fresh glass shards, indicating the eruption of new magma. Satellite imagery tracked these plumes as they moved eastward and disrupted commercial airline traffic to and from Alaska.\r\n   \"A 16 January overflight revealed a small, new lava dome at the summit. An explosive eruption at 1658 UTC on 17 January sent ash to 13 kilometers asl that moved westward. The eruption left a 20- to 30-meter-diameter crater in the new dome and produced ballistic fields on the volcano's western flanks. Data transmission from the west flank CGPS station stopped coincident with this explosion [see figure 2 in original text]. Additionally, the eruptions of 13-17 January generated pumiceous pyroclastic flows, snow avalanches, and lahars that moved down the volcano's flanks [see figure 2 in original text].\r\n   \"The volcano then entered a period of more continuous eruptive activity that began at 0534 UTC on 28 January and that lasted until 2 February. The phase began with four explosive eruptions that generated ash plumes to heights of nine kilometers asl [ see figure 3 in original text]. Ash moved southward and fell in trace amounts on Kodiak Island. These explosions generated substantial pumiceous pyroclastic, block, and ash flows that destroyed seismic and CGPS stations on the west and north flanks of the volcano [see figure 2 on original text]. Destruction of these seismometers compromised AVO's ability to assign reliable hypocentral depths to earthquakes.\r\n   \"Data from the remaining CGPS stations indicated that the volcano reversed its long inflationary trend (during which accumulating magma caused a swelling of the volcano's surface) and began a sharp deflation that continued until 10 February [see figure 3 in original text]. Modeling suggests the locus of deflation, which results from the removal of magma, was much deeper (~10 kilometers) than the precursory signal. On 29 January, the seismic network began to detect numerous block and ash flows - generated by small failures of the growing lava dome - cascading down the volcanos northern flanks [see figure 2 in original text].\r\n   \"Augustine then entered an effusive phase, which lasted through late March. From 2 February through 6 March, block and ash flow signals continued to dominate the seismic record. Geodetic data showed inflation from 10 February until 1 March, when the volcano again reversed and entered an 11-day period of deflation [see figure 3 in original text]. On 7 March, seismic activity again shifted to small, mostly identical repetitious earthquakes. These events increased in rate and size, forming a continuous signal early on 8 March that lasted until 14 March. They then began a slow decline and disappeared by 16 March. Lava extrusion at the summit increased markedly in association with these repetitive earthquakes, and two blocky lava flows moved down the north and northeastern flanks [see figures 1 and 2 in original text]. Observations indicate that the effusion of lava stopped in late March. The volcano entered a final period of inflation between 12 and 31 March. The estimated volume of effusively erupted material is currently 30 million cubic meters.\"\r\n\r\nMcGimsey and others (2011) report that throughout 2007, continued cooling from the 2005-2006 eruption, steam plumes, and anomalous seismicity were observed at Augustine.","StartYear":2005,"StartMonth":12,"StartDay":null,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2006,"EndMonth":3,"EndDay":31,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Augustine","ParentVolcano":"Augustine","VolcanoID":"ak20","ParentVolcanoID":"ak20"},{"ID":596,"Name":"Shishaldin 2005/12","Description":"   From McGimsey and others (2007): \"Following more than a year of relative quiescence, on December 22, 2005, a pilot reported a steam plume rising 3,000 ft above the summit of Shishaldin.  The FAA issued an Urgent Pilot Report.  Commensurate with this report, a few small explosions were recorded on the pressure sensor located on the north flank.  AVO seismologists also noted that the amplitudes of seismic events had increased since about mid-November.  Because no ash apparently was released and the activity did not continue, AVO did not issue a formal information release nor increase the level of concern color code.\"","StartYear":2005,"StartMonth":12,"StartDay":22,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2005,"EndMonth":12,"EndDay":22,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Shishaldin","ParentVolcano":"Shishaldin","VolcanoID":"ak252","ParentVolcanoID":"ak252"},{"ID":607,"Name":"Martin 2006/1","Description":"   From Neal and others (2009): \"On January 10, 2006, AVO raised the Level of Concern from GREEN to YELLOW after a sharp increase in earthquake activity beneath Mount Martin that had begun on January 8 (Dixon and others, 2007). Roughly 300 earthquakes were located in just over 2 days [see fig. 38 in original text], a significant increase over the long-term average rate of less than one event per day since the seismic network was installed in 1996. Satellite data did not indicate any obvious changes at the surface.\r\n   \"Elevated seismicity continued for about 2 weeks after which the rate of shallow volcano-tectonic earthquakes decreased to levels considered background for Mount Martin. On January 27, AVO downgraded the Level of Concern to GREEN. Throughout this seismic swarm, no surface manifestations of the increase in seismicity were noted in satellite imagery or by passing pilots. The cause of this swarm remains uncertain (John Power, USGS, oral commun., 2007).\"","StartYear":2006,"StartMonth":1,"StartDay":8,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2006,"EndMonth":1,"EndDay":22,"EndTime":null,"EndQualifier":2,"EndQualifierUnit":"Days","Volcano":"Martin","ParentVolcano":"Martin","VolcanoID":"ak189","ParentVolcanoID":"ak189"},{"ID":608,"Name":"Korovin 2006/1","Description":"From Neal and others (2009): \"Beginning on January 16, a brief (minutes-long) increase over this background level was noted. Additional bursts of tremor-like signals occurred on January 17-18, 21, and February 21-22, prompting AVO to raise the Level of Concern Color Code to YELLOW. Satellite imagery of the volcano showed nothing unusual, although clouds frequently obscured the region. AVO did not receive reports of activity from residents of Atka Village, despite periods of clear weather in late February.\r\nSeismicity stabilized and then decreased in early March, and AVO downgraded the Level of Concern Color Code to GREEN on March 8. Clear satellite looks and overflights by commercial pilots indicated no significant surface changes in the vicinity of Korovin. In the spring, there were several week-long outages where fewer than the minimum number of stations required to locate earthquakes were operational.\r\n   \"The number of earthquakes in the vicinity of Korovin began to increase again in July. Episodes of volcanic tremor were recorded again in September and October, increasing in number, strength, and duration into the fall. White plumes of water vapor reaching several hundred meters above the volcano were photographed from Atka on October 29 [see fig. 44 in original text], about coincident in time with a strong tremor burst about 5 minutes in duration captured on the Korovin network. The shallow lake in the main Korovin crater, present on September 12 according to satellite data, had disappeared by October 19, and remained absent through the end of the year. On November 5, the strongest earthquake swarm ever recorded by the AVO seismic network occurred. AVO decided to upgrade the level of concern for Korovin, based on this sustained increase in seismic activity and visual confirmation of increased fumarolic activity and disappearance of the lake. Utilizing the new warning scheme adopted by the United States Volcano Observatories in October, AVO declared Aviation Color Code YELLOW and Volcanic Activity Alert Level ADVISORY for Korovin on November 6.\r\n   \"Seismicity at Korovin remained above background through the year's end. Periodic strong, short-duration (tens of seconds to several minutes) signals recorded on the entire network may have been phreatic explosions or sudden hydrothermal boiling events. Similarly, several-minute-long, low-frequency tremor bursts at rates of several per hour occurred intermittently. ASTER satellite images from November 18 indicated an exposure of dark-gray ash on the eastern flank of Korovin's main crater [see fig. 45 in original text]; this ash was not present in a similarly clear image from November 21. Still, it is not known exactly when and by what process ash was emitted from Korovin; it also is possible that the ash visible in satellite imagery represents remobilization of older ash high on the cone, as may have been photographed during fieldwork in 2004 [see figs. 46 and 47 in original text]. Thermal bands in ASTER imagery showed warm areas in the Korovin crater, not a surprise given the known, ongoing fumarolic activity within the crater [see fig. 46 in original text].\r\n   \"In late November, AVO learned that the Korovin volcano area had undergone significant deformation during the second half of the year. InSAR results comparing data from July and October 2006 for Korovin indicated a very prominent, circular pattern of uplift of as much as 5 cm (2 in) centered about 5.5 km (3.4 mi) southwest of Korovin (see fig. 48 in original text; Z. Lu and P. Cervelli, USGS, written commun., 2006). This location generally is consistent with locations of earthquake swarms beginning in the summer. Two possible explanations for this uplift were considered: (1) a pressurizing and inflating hydrothermal system, plausible given the robust, disseminated hot springs around Korovin and neighboring Kliuchef volcanoes (Motyka and others, 1993) or (2) a rising magmatic intrusion and related deformation.\r\n   \"Residents of Atka continued to photograph particularly large, at times 'puffing' white-vapor plumes emanating from Korovin on December 11, 21, and 24 [see figs. 49 and 50 in original text]. At least one of these reports suggested the possibility of ash within the plume; the observer further clarified that he saw ash falling below the cloud after it attained some altitude. Ash on the ground was not verified. Satellite data did not detect any rise in ground temperature nor any ash in the atmosphere or on the ground through the end of 2006.\r\n   \"AVO tracked activity at Korovin using seismic and satellite data. Several times during the year, AVO staff contacted Atka residents by telephone or email to gather additional observations or clarify AVO reports. In February, AVO asked Peninsula Airways (Pen Air) pilots flying into Atka to pass along any pertinent observations. On February 22, Pen Air reported no sign of ash or anything unusual at the volcano.\"\r\n\r\nFrom McGimsey and others (2011): Korovin Volcano on Atka Island in the west-central Aleutians began 2007 in Aviation Color Code YELLOW and Volcano Alert Level ADVISORY following an upswing in activity during 2006 (Neal and others, 2008). A relatively high level of background seismicity has been prevalent since the AVO network was installed in 2004, and a higher level of seismicity that began in 2006 continued into the first half of 2007 [see figs. 45 and 46 in original text].\r\n   \"Reports of steam clouds on December 24, 2006, were followed on January 11, 2007, by a M3.5 earthquake at Korovin, which is considered quite large for volcano-generated seismicity. A swarm of likely associated events were recorded during the week; however, a M8.2 earthquake in the Kurile Islands on January 12 (AKST) also may have triggered seismicity at Korovin.\r\n   \"On January 23, a series of tremor bursts were recorded, and on January 24, AVO received photographs from an Atka Village resident of a steam column rising from Korovin's active crater [see fig. 47 in original text]. The observer reported similar steam columns rose up to about 1,000 ft (about 300 m) above the volcano every 15 to 80 minutes. Satellite images from the previous week indicated that the intermittent lake in Korovin's active crater was not present. Previously, in late September or early October 2006, the lake disappeared following a strong episode of steam emission. The lake had not re-appeared as of mid-January 2007.\r\n   \"The next report of activity at Korovin came on the afternoon of February 14 when NWS contacted AVO to pass on a PIREP from a U.S. Coast Guard C-130 of a steam plume extending 5,000-8,000 ft (about 1,500-2,400 m) over Korovin. A SIGMET was not issued.\r\n   \"A couple of weeks later, Atka Village residents Lynn and Kerry Moore sent photographs to AVO taken on March 3 of an ash deposit on the west flank of Korovin [see fig. 48 in original text]. Prior to taking the photographs, the Moores observed steam rising from the active, south summit vent. No anomalous activity was noted in AVO satellite reports for that day; however, a flurry of low frequency seismicity occurred that morning, comparable to seismicity of the last few months. Phreatic activity at Korovin produced similar ash deposits in 2004 and 2006 (Neal and others, 2008).\r\n   \"Episodes of tremor occurred over several days in May, June, and August, and a thermal anomaly was detected in satellite images in early August. Steam plumes were observed by residents in Atka Village in late July [see fig. 49 in original text]. The satellite-based Ozone Monitoring Instrument (OMI) detected a small SO2 cloud located about 300 km (186 mi)north of Cleveland volcano on August 5, 2007, that likely originated at Korovin based on wind dispersal models. An aerial photograph taken that day shows a steam plume wafting from the crater (fig. 50). On August 19, a flurry of 33 detected seismic events located 4 km (2.5 mi) southeast of Kliuchef was detected [see figures 50 and 52 for location of Kliuchef, 6.5 km (4 mi) south of Korovin]. This was followed on August 20 by a small emission of SO2 from Korovin that was detected by OMI [see fig. 51 in original text].\r\n   \"Inflation beneath the northern part of Atka Island that began in June 2006 and totaled 9-10 cm (3.5-3.9 in.) of uplift, had begun to taper off in 2007 (Zhong Lu and Peter Cervelli, USGS, written commun., 2007). An InSar interferogram acquired July 1, 2007, shows a distinct but weakened anomaly still centered on the west flank of Kliuchef volcano [see figs. 52 and 53 in original text]. Seismicity over the same period appears to have tracked the uplift (P. Cervelli, USGS, written commun., 2007); compare the area of uplift with the located seismicity in figure 53.\r\n   \"The decreasing trends of seismicity and uplift prompted AVO to begin considering a status change for the volcano, which had been at Aviation Color Code YELLOW and Volcano Alert Level ADVISORY since November 6, 2006. On September 7, 2007, the Aviation Color Code/Volcano Alert Level was downgraded to GREEN/NORMAL. Although circuit problems plagued the Atka Island network on several occasions, activity at Korovin was uneventful for the remainder of 2007.\r\n   \"AVO tracked activity at Korovin using seismic and satellite data, and occasional pilot reports. Several times during the year, AVO staff contacted Atka residents by telephone or email to gather additional observations or clarify AVO reports.\"","StartYear":2006,"StartMonth":1,"StartDay":16,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2007,"EndMonth":9,"EndDay":null,"EndTime":null,"EndQualifier":2,"EndQualifierUnit":"Months","Volcano":"Korovin","ParentVolcano":"Atka volcanic complex","VolcanoID":"ak171","ParentVolcanoID":"ak17"},{"ID":552,"Name":"Cleveland 2006/2","Description":"From Neal and others (2009): \"The first known explosive eruption [at Cleveland Volcano]  in 2006 occurred on February 6, and was detected in routine Advanced Very High Resolution Radiometer (AVHRR) satellite image analysis by anomaliesAVO staff. Satellite-derived temperatures indicated an initial cloud height of about 6-8 km (22,000-26,000 ft). The eruption appeared to be short lived and had ceased several hours before detection on satellite imagery, but AVO raised the Level of Concern Color Code to RED and NWS issued a SIGMET. The cloud was tracked for more than 400 km (250 mi) southeast of the volcano before it largely dissipated in satellite images. By day's end, with no further reports or images of ash production at Cleveland, AVO downgraded the Color Code to ORANGE. For the duration of condition RED, the FAA imposed a temporary flight restriction (TFR) from the surface to 50,000 ft within a 5 nautical mile radius of the volcano.\r\n   \"AVO downgraded Cleveland to Color Code YELLOW 5 days later on February 11. Cloud cover persisted during most of this interval, and AVO's information release on February 11 noted that undetected, low-level unrest could continue. No further indication of activity led AVO to further downgrade Cleveland to a Color Code of 'Not Assigned' on February 20. (AVO policy is that a volcano lacking seismic instrumentation cannot be known to be at background, and hence cannot be assigned a Color Code GREEN).\"\r\n\"On May 5, AVO reported a thermal anomaly and continuous plume of volcanic gas from Cleveland. The plume was visible over the course of 6 hours but traveled only 48 km (30 mi) southwest of the volcano and appeared to be at a relatively low altitude and devoid of ash. Cleveland remained 'Not Assigned.'\r\n   \"On May 23, an astronaut aboard the International Space Station (ISS) contacted ground control with a report of an eruption from a volcano in the Aleutians. Subsequent communication with AVO, including receipt of a photograph [see fig. 41 in original text, and \u003ca href=\"http://www.avo.alaska.edu/image.php?id=10064\"\u003ehttp://www.avo.alaska.edu/image.php?id=10064\u003c/a\u003e online] and a telephone call from the ISS, confirmed Cleveland as the source. The plume was ash rich and by the time it was detected in AVHRR imagery, it was a detached ash cloud about 130 km (80 mi) southwest of the volcano. Satellite cloud-temperature data indicated a cloud top of about 6,700 m (22,000 ft) ASL. AVO raised the Level of Concern Color Code for Cleveland to YELLOW, and subsequently downgraded to 'Not Assigned' on May 26 after no further activity was detected.\r\n\"On August 24, AVO received notice from NWS that a ship had reported an ash eruption from Cleveland volcano. Days later, AVO received video footage from the crew of this fishing vessel showing a definite ash plume reaching about 3 km (~10,000 ft) ASL [see fig. 42 in original text]. Importantly, neither a broadband regional network seismic station in Nikolski [see fig. 1 in original text; M. West, UAFGI, written commun., 2006) nor any time-correlative satellite imagery showed evidence of this eruption. On September 7, after reviewing video footage of the August 24 event and noting an intermittently present thermal anomaly at the volcano, AVO raised the Level of Concern Color Code to YELLOW.\r\n   \"AVO was alerted by NWS of another Cleveland eruption on October 28 after a pilot report to the Anchorage Air Traffic Control Center. The pilot of a jetliner indicated an initial cloud over the volcano reaching their flight level of 36,000 ft (11,000 m) ASL, and a drifting cloud moving east-northeast at a lower level of 30,000 ft (9,100 m) ASL. Satellite-derived cloud top temperature estimates placed the plume much lower. Utilizing the new warning scheme adopted by United States Volcano Observatories in October, AVO declared Aviation Color Code ORANGE and Volcanic Activity Alert Level WATCH for Cleveland about 2 hours after receipt of the pilot report, and reverted to YELLOW/ADVISORY on October 30 after no indications of further activity. On clear days under optimal satellite viewing conditions, a weak thermal anomaly was detected in the vicinity of the summit crater at Cleveland into November [see fig. 43 in original text].\r\n\"Ash explosions likely occurred more often at Cleveland than were detected in either satellite imagery or by pilots or other observers. An infrasonic signal received at the Geophyiscal Institute in Fairbanks on November 6 may have been produced by an explosion at Cleveland (or a nearby volcano); however, with no corroborating evidence, AVO took no action (S.R. McNutt, UAFGI, written commun., 2006).\"","StartYear":2006,"StartMonth":2,"StartDay":6,"StartTime":"15:00:00","StartQualifier":15,"StartQualifierUnit":"Minutes","EndYear":2006,"EndMonth":11,"EndDay":20,"EndTime":"17:00:00","EndQualifier":2,"EndQualifierUnit":"Hours","Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":569,"Name":"Veniaminof 2006/3","Description":"   From the Smithsonian Institution (2006, v. 31, n. 3): \"On the morning of 3 March 2006 ash again rose a few hundred meters above the intracaldera cone, drifted E, and dissipated rapidly. Ashfall was expected to be minor and confined to the summit caldera. Seismicity was again low and did not indicate that a significantly larger eruption was imminent. Over the week of 5-10 March, seismicity was low but slightly above background.\r\n   \"On the morning of 10 March, AVO received a report from a pilot of low-level ash emission from the intracaldera cone. Clear web-camera views on 9 March showed small diffuse plumes of ash extending a short distance from the intracaldera cone. The Anchorage Volcanic Ash Advisory Center (VAAC) reported a steam/ash plume noted on web-cam and satellite on 13 March 2006 at 0500Z (12 March 2006 at 2000 hours local), moving NNW at 9.2 km/hr and falling to the land surface. Web-cam images on 22 March showed a very diffuse steam-and-ash plume that was confined to the summit caldera, and on 24 March showed a steam-and-ash plume drifting from the summit cone at a height of less than 2.3 km. This level of activity was similar to that on 23 March, but higher than activity on 21 and 22 March, when a very diffuse steam-and-ash plume was confined to the summit caldera.\r\n   \"The flow of seismic data from Veniaminof stopped on the evening of 21 March 2006, and the problem was expected to continue until AVO staff could visit the site to repair the problem. Absent seismic data, the volcano could potentially still be monitored in other ways such as using web-camera and satellite images. Imagery was obscured by cloudy weather after 21 March. On 26 March 2006, a pilot reported a small ash plume rising above the volcano. Low-altitude ash emissions from Veniaminof were visible during 31 March to 7 April. On 6 April, a pilot reported an ash plume at a height of 3 km. AVO stated in its weekly report of 14 April 2006 that the seismicity at Veniaminof remained low but above background. Internet camera and satellite views had been obscured by cloudy weather, and AVO lacked new information about ash clouds or activity.\"\r\n   Continued activity was summarized by the Smithsonian Institution (2006, v. 31, n. 8): \"Intermittent, very small-volume steam and ash bursts from the intra-caldera cone have been typical of this volcano intermittently over the past few years, and this pattern continued. The previous report mentions several minor bursts of ash, particularly on 13 June 2006 and 7 September, and minor white plumes through mid-September. This report discusses the interval 8 April through 15 September. Seismicity during this interval was nearly always low, although it often rose above background.\r\n   \"Clouds obstructed visibility during 7-14 April. For the duration of April and June, activity remained low with few steam plumes containing minor amounts of ash. On 30 May a weak daytime thermal anomaly was recorded, possibly due to solar heating inside the dark intra-caldera cone. Intermittent clear weather on the week ending 9 June indicated weak steam plumes.\r\n   \"On 13 June an ash emission rose to a height estimated at ~ 600 m above the summit area, as reported by a passing aircraft. Transient plumes were seen on satellite imagery during the week ending 21 July.\r\n   \"During the week ending 28 July, an AVO field party flew over the summit and observed typical steaming from the intra-caldera cone with no signs of recent ash emissions. Satellite and web camera views during occasional clear periods showed no other signs of activity. Occasional satellite views during clear weather failed to disclose new ash emissions during 28 July through 15 September.\r\n   \"AVO noted a slight increase in seismicity starting 2 August but in the subsequent weeks it again returned to low levels. Available satellite and camera views continued to reveal occasional small white plumes through 15 September.\"\r\n  Steam plumes without ash emission continue to be observed at Veniaminof, as of this writing (March 21, 2007).  \r\n\r\nMcGimsey and others (2011) report that by January 2007, the intracaldera cinder and spatter cone was producing only minor, diffuse steam plumes that rose at most a few hundred meters above the vent. * * * Foloowing several weeks of cloudy weather, clear web camera views on the morning of February 16, 2007, revealed vigorous steaming from the intracaldera cone [see fig. 22 in original text]. Clouds and a short camera outage prevented observations for several days, and then on the morning of February 20, a clear view showed little to no steaming from the cone. Minor steaming was visible through February 24 when weather permitted, and by February 25, no signs of steam emissions were apparent in web camera images. Over the next couple of months, intermittent clear views of the volcano in either web camera images or in satellite images showed that occasionally minor steam plumes were issuing from the intracaldera cone. Seismicity had decreased to background levels several months prior, and the last ash-laden plume visible in web camera images was on November 2, 2006. The last thermal anomaly visible in satellite images was on July 5, 2006. Ground observers and pilots reported no unsual activity in recent months, and therefore on April 26, 2007, AVO lowered the Aviation Color Code/Volcano Alert Level to GREEN/NORMAL. Based on historic patterns of eruptive behavior, AVO anticipated continued steaming from the cone. Indeed, Veniaminof continued to steam intermittently throughout 2007.\"\r\n\r\nFor additional photographs and observations of this event, please see: Neal, C.A., McGimsey, R.G., Dixon, J.P., Manevich, Alexander, and Rybin, Alexander, 2009, 2006 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Scientific Investigations Report 2008-5214, 102 p., available at \u003ca href=\"http://pubs.usgs.gov/sir/2008/5214/\"\u003ehttp://pubs.usgs.gov/sir/2008/5214/\u003c/a\u003e.","StartYear":2006,"StartMonth":3,"StartDay":3,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2006,"EndMonth":11,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Veniaminof","ParentVolcano":"Veniaminof","VolcanoID":"ak301","ParentVolcanoID":"ak301"},{"ID":555,"Name":"Fourpeaked 2006/9","Description":"From Neal and others (2009): \"As fall arrived in Alaska, a phreatic eruption from a volcano not considered active in the Holocene surprised AVO and residents of south-central Alaska. Late on Sunday, September 17, AVO received several citizen telephone reports of a dark plume, fed by what appeared to be two sources, rising from the area near Cape Douglas in lower Cook Inlet. Satellite analysis indicated the source of the plumes to be roughly between closely spaced Douglas and Fourpeaked volcanoes. he drifting cloud produced by these rising plumes persisted throughout the night, reaching a minimum altitude of 20,000 ft (6,100 m based on radar data; Dave Schneider, USGS, written commun., 2006), but drifting only 20 km (12 mi) downwind in an unusually calm and clear atmosphere over south-central Alaska. \r\n   The next day, AVO issued an information release mentioning Douglas and Fourpeaked volcanoes, but stated that the exact nature and source of the plumes remained unclear. Neither volcano was monitored seismically, and data from the nearest stations at Katmai and Augustine initially showed nothing dramatic. Deteriorating weather conditions precluded visual observations, but an overflight was scheduled for the first clear window. On the afternoon of September 18, NWS relayed a pilot report of a strong sulfur odor 300 km (190 mi) northwest of Fourpeaked. This was an area likely to be impacted by drift of the September 17 cloud according to PUFF, a volcanic ash tracking model used by AVO (Searcy and others, 1998). Pilots in the Lake Iliamna area on the morning of September 18 also reported a strong sulfur odor, a locality also consistent with likely cloud drift on the 17th.\r\n    On September 20, AVO received NWS radar and other satellite data indicating particulate and sulfur-bearing properties in the cloud of September 17, confirming a volcanic source for the event. Based on this, AVO announced Level of Concern Color Code YELLOW for both Douglas and Fourpeaked volcanoes because the source was still uncertain. NEXRAD Doppler radar images from King Salmon showed a particulate cloud in the atmosphere from at least 12:00 p.m. to 9:45 p.m. ADT on September 17. The cloud appeared most energetic (dense) in the first 2 hours (Dave Schneider, USGS written commun., 2006). The bulk of the cloud remained over the point of origin for much of this time, reflecting very calm atmospheric conditions on that day. In addition, Ozone Monitoring Equipment onboard National Aeronautics and Space Administration's (NASA) Aura satellite indicated a pod of SO2 gas in the general vicinity of the eruption plume at 3:00 p.m. ADT. Subsequently, AVO received reports of a very fine-ash dusting at Nonvianuk Lake outlet (110 km or 70 mi west northwest of Fourpeaked) and near Homer (150 km or 90 mi northeast of Fourpeaked). The Nonvianuk report stated, 'We have a heavy sulfuric smell in the air and ash filling the air. The wind here is blowing from the ESE' No samples were retrievable from either location for analysis, but the Nonvianuk report is consistent with PUFF trajectories for a cloud reaching about 20,000 ft (6,100 m) on the afternoon of September 17. Interestingly, multi-spectral satellite images showed no ash signature in the plume on September 17, but AVO analysts did note a thermal anomaly in the vicinity of Fourpeaked (J. Dehn, University of Alaska Fairbanks Geophysical Institute (UAFGI), written commun., 2006). Following the initial event on September 17th, no further particulate clouds were imaged by radar or other means. \r\n   An AVO overflight on September 20 confirmed Fourpeaked as the source of volcanic activity. Despite cloud cover of the actual summit, observers in a fixed-wing aircraft circled several distinct vapor clouds rising through the cloud deck above Fourpeaked. Visible patches of discolored snow and ice, especially north and west of the Fourpeaked summit, suggested ash fallout. An AVO helicopter crew later on the same day photographed a lobate, dark debris-flow tongue that had emerged from glacial ice about 3,000 ft (900 m) below the cloud-covered Fourpeaked summit; patchy areas of grey ash on the glacial ice around the summit and to the northeast also were noted. Clouds and fuel limitations prevented any further exploration of the area. \r\n   Aerial inspection of the Fourpeaked area on September 23 finally revealed the source of the September 17 plume and continuing fumarolic emissions. Water vapor and volcanic gas billowed from a dramatic, linear series of pits or vents extending about 1,250 m (4,100 ft) across the heavily crevassed and disrupted glacial-ice cover on the north side of the summit region. Multiple sources of vapor from these vents explain the apparent double plume seen in the photograph of September 17. A light dusting of dark material surrounded some of the open pits and several elongate dark stripes leading down slope from at least one vent probably represented remobilized fragmental ejecta mixed with melted ice and snow (or plume condensate). A subtle series of snow-mantled rills leading down slope in the same area indicated several episodes of surface debris or water flow. Stormy weather between September 17-23, produced new snowfall indicating that the ejecta collars and small debris flows observed on September 23 had occurred after the initial event.\r\n   AVO scientists visited the area by helicopter on September 24 and 25. The vent area consisted of as many as nine discrete craters or pits, and between three and five were venting steam and volcanic gas at any one time. The vents occurred along a line trending north from the summit basin, inferred to be a glacial cirque, obliquely down-slope across a northwest trending, ice-covered ridge. The bottoms of non-steaming pits were covered with blocks of debris-mantled ice. The upper craters within the Fourpeaked summit cirque had coalesced creating a heavily disrupted ice zone. Most craters were surrounded by fine (?) debris collars that did not extend very far from their rims; there was no evidence of additional, significant ash emission since September 17. FLIR imaging of the pits indicated elevated temperatures as high as 75C (167F); however, these values are minimums due to steam obscuration. A strong sulfur odor was noted downwind of the vents as far as 50 km (30 mi).\r\n   The glacial outburst associated with the September 17 event originated from beneath a chaotic ice jumble on the unnamed north-trending glacier at an elevation of about 5,000 ft. This flood apparently scoured a steep-walled canyon more than 100 m (330 ft) deep in places. Blocks of ice up to 5 m (16 ft) or more across had been rafted in a mixture of water and fine-grained to cobble-boulder sized, heterolithologic volcanic debris at least 6 km (4 mi) down slope, where material spilled off the front of the glacier ice and traveled an unknown distance into the Douglas River drainage. Levees of ice, sediment, and rock clasts as much as 10-15 m (33-50 ft) high marked the margins of the deposit. Where traced into the Douglas River drainage about 3-4 km (2-2.5 mi) from the glacier snout, the deposit was thin (about 2 cm or 0.8 in) and fine grained with a maximum clast size of about 1 cm (0.4 in). The field crew flew the length of the Douglas River to Cook Inlet and noted evidence of a flooding event represented by recently emplaced fine-grained gray sediment on beaches and river banks. On the day of observation, there was no evidence of continuing discharge of meltwater or debris down this newly carved drainage system. \r\n   AVO scientists collected samples of the fine, gray ash-fall deposit from the September 17 event. Deposits were most impressive west of the vent area where they were estimated to be 1-2 mm (less than 0.1 in) thick. Other flanks of the volcano received a mere dusting (\u003c1 mm); based on these few observations and the outlier reports of extremely light ash fall noted at two distant locations, the fall deposit likely represents well under 1 million cubic m of material. Preliminary petrographic analyses indicate the tephra consists of hydrothermally altered volcanic rock and crystal fragments, notably pyrite, and other accessory minerals (J. Larsen, UAFGI, written commun., 2006).\r\n   AVO geologists in the field on September 24-25 also reported loud rumbling sounds associated with sudden bursts of water from the ice-bedrock contact at an elevation of approximately 4,000 ft on the northwest flank of Fourpeaked; these flows lasted several seconds and then disappeared. An overflight of the cliff below these outbursts did not reveal anything unusual, and any relationship between these periodic outbursts of water with the events of September 17 is uncertain. \r\n   AVO geologists made further ground-based observations of the deposits and features related to this unrest in mid-October. Close helicopter passes of the vent area on October 14 revealed that several of the original craters had coalesced and the rims of the sheer-walled pits had retreated, enlarging most by perhaps tens of meters. The pit rims were blanketed by fresh snow indicating no additional ash emission of significance since the explosion on September 17. However, intermittent, vigorous fumarolic activity capable of entraining a small amount of locally derived material may have continued and gone undetected between overflights. Field observers saw no sign of large ballistics littering the surface, so any ongoing phreatic emissions were not very energetic. Yellow-stained (most likely sulfur) snow surrounded the upper crater. \r\n   Deposits related to the outburst flood into the Douglas River were examined more closely and consisted of gray, soggy, water-saturated, sulfur-smelling silty material containing cobble-sized clasts of dense, altered, volcanic rock and pyrite (and possibly marcasite). Preliminary results from x-ray diffraction and x-ray fluorescence analyses of a non-pyritic material indicate that the volcanic rock composition primarily is dacite, and that the fine fraction also contains minor gypsum and minor smectite (K. Bull, ADGGS, written commun., 2007). Interestingly, near the snout of the glacier impacted by this outburst flood, AVO geologists noted multiple layers of similar, sulfurous, heterolithologic material exposed in the ice stratigraphy, and postulated that these may represent prior (possibly historical in age) debris-flow events captured in the ice. \r\n   Eight airborne gas measurements were obtained between September 23 and November 18, 2006. Sulfur dioxide output was steady and high for a non-erupting volcano ranging between 820-2,940 ton/d (Doukas and McGee, 2007). For the same period, CO2 flux was between 340-834 ton/d. In contrast to Augustine Volcano (McGee and others, 2006), H2S output from Fourpeaked remained quite high, between 70-140 ton/d, likely reflecting the dominance of a wet hydrothermal system at this ice-clad volcano. In addition to these onsite, airborne measurements, Ozone Mapping Instrument (OMI) sensors occasionally detected SO2 clouds in the area. Beginning in October, low sun angles prevented good results and AVO stopped receiving reports from the OMI satellite team at the University of Maryland (D. Schneider, USGS, oral commun., 2006).\r\n   Seismic activity as recorded on the three new stations installed following the event on September 17 remained relatively low through the end of the year, typically with only a few volcanic earthquakes captured on most days. These three stations augmented coverage by regional seismic station CCDN about 17 km (~11 mi) northeast of Fourpeaked. On October 3, a swarm consisting of tens to hundreds of very small, non-locatable earthquakes occurred in the vicinity of Fourpeaked. A second swarm on November 5-6 occurred within the new Fourpeaked subnet and 75 events were located. Seismicity remained elevated with occasional small swarms of activity (10 located events per day or less) through the end of the year. Small explosion signals also began to be recorded in the spring; these signals may have reflected transient increases in fumarolic emission.\r\n   Further analysis of Katmai area seismic stations during the time period of the eruption cloud and opening of vents in the ice revealed a small swarm of earthquakes between 11:48 a.m. and 3:50 p.m. ADT on September 17 (M. West, UAFGI, oral commun., 2006) coincident in time with the onset and development of the plume seen in radar images. The University of Alaska Fairbanks infrasound array also detected a signal at about 20:50 UTC on September 17, likely an explosion source, at a time and location consistent with the plume sighting (S.R. McNutt, UAFGI, oral commun., 2006). \r\n   AVO concluded that the unrest at Fourpeaked volcano most likely involved the presence of new magma at fairly shallow (less than a few kilometers) levels, accounting for the seismicity and degassing, and providing a heat and gas source for a phreatic explosion, vigorous phreatic emission of gas and fine particulates, and a glacial outburst of meltwater, glacial ice, and hydrothermally altered debris on September 17. \r\n   A shallow, degassing intrusion of fresh magma also would account for the ongoing gas emissions (K. McGee, USGS, oral commun., 2006). The lack of a seismic network at Fourpeaked precludes exact determination of the onset of seismicity that may have been associated with an intrusion. However, the swarm detected on the Katmai network on September 17 likely captured the most vigorous phase of the event, including the onset of phreatic eruption. \r\n   Through the remainder of 2006 and into 2007, a variably robust plume of vapor and volcanic gas discharged from the linear chain of pits in the ice. Overflights into mid-November documented minor changes in the pit morphologies, primarily related to coalescence and widening. No further ash emissions of significance were noted, although an increasingly visible coating of a yellow, likely sulfurous deposit stained snow and ice cover around the Fourpeaked summit.\" \r\n\r\nFor detailed observations and photographs of this event, pelase see: Neal, C.A., McGimsey, R.G., Dixon, J.P., Manevich, Alexander, and Rybin, Alexander, 2009, 2006 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: Summary of events and response of the Alaska Volcano Observatory: U.S. Geological Survey Scientific Investigations Report 2008-5214, 102 p., available at \u003ca href=\"http://pubs.usgs.gov/sir/2008/5214/\"\u003ehttp://pubs.usgs.gov/sir/2008/5214/\u003c/a\u003e .\r\n\r\nMcGimsey and others (2011) report that throughout the first half of 2007, seismicity, steaming, and gas emissions decreased at Fourpeaked following the 2006 eruption. McGimsey and others (2014) continue the chronology of this event: \"Steam and gas emissions were frequently observed in web camera images and during routine gas measurement flights through the first half of 2008, and were visible to an AVO field crew on Augustine Volcano in July 2008 (AVO internal log entries). Activity continued to decrease into, and through 2009.\r\n    \"Steam plumes were visible in the web camera on February 8, 2009, and during gas measurement flights on June 6, 2009, and November 2, 2009; during the November overflight, no gas was detected (M. Doukas, U.S. Geological Survey, written commun., 2012). As the phreatic activity diminished, the melt holes begam filling with snow and fumarolic activity was observed only from a single vent. \r\n   \"The seismic and infrasound networks, and the web cam, were serviced in the summer of 2008, and a year later, as the batteries drained, the instruments stopped recording data. On November 18, 2009, prompted by the network outage and inability to assess the level of seismic activity, AVO issued a Volcanic Activity Notice and an Information Release downgrading Fourpeaked from Aviation Color Code GREEN and Volcano Alert Level Normal to UNASSIGNED, thus removing it from the list of seismically monitored volcanoes.\"","StartYear":2006,"StartMonth":9,"StartDay":17,"StartTime":"12:00:00","StartQualifier":10,"StartQualifierUnit":"Minutes","EndYear":2006,"EndMonth":9,"EndDay":17,"EndTime":"21:45:00","EndQualifier":30,"EndQualifierUnit":"Minutes","Volcano":"Fourpeaked","ParentVolcano":"Fourpeaked","VolcanoID":"ak103","ParentVolcanoID":"ak103"},{"ID":642,"Name":"Akutan 2007/1","Description":"   From McGimsey and others (2011): Akutan is one of several Alaska volcanoes at which seismicity was triggered by the M8.2 earthquake generated in the Kurile Islands on January 13, 2007, 0423 UTC. Four of the seven largest triggered Akutan events, ranging in magnitude from 0.0 to 0.5 and depths from 0.86 to -2.17 km, were located (see fig. 36 in original text; John Power, AVO/USGS, written commun., 2010). The earthquake locations fall along the trend of intense seismicity and ground breakage that occurred in March 1996 at Akutan (Neal and others, 1997; Waythomas and others, 1998, fig. 10; Lu and others, 2005). The AVO Akutan seismic network was installed in the summer of 1996, and this was the first instance of observed triggered seismicity at Akutan; however, it was short-lived and did not result in any detectable surface disturbance.\r\n   \"In early October 2007, AVO remote sensors using GPS time series for Akutan detected signs of renewed inflation over the previous month of the west flank, the same area that inflated during the 1996 seismic crisis. A few days later, on October 8, the manager of the Trident seafood processing plant called to alert AVO of 'strong steaming' from a 'new' area in the Hot Springs Bay valley [see fig. 37 in original text]. Long-known thermal springs occur along the lower course of the stream draining the valley, and the photograph of figure 37 shows a steam column apparently rising from further up-valley of the springs area. This also is the area of maximum deflation following the 1996 seismic swarms. No unusual seismic activity was noted for the period of west-flank inflation or this steaming episode. This location for a steam plume was considered 'new' by local observers because the lower-valley thermal springs rarely emit a concentrated, vertically rising plume of steam and most reports of steaming arise from the prominent fumarole field located at the 1,500-ft-level of the eastern flank at the headwaters of Hot Springs Bay valley [see fig. 38 in original text].\"","StartYear":2007,"StartMonth":1,"StartDay":13,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2007,"EndMonth":10,"EndDay":null,"EndTime":null,"EndQualifier":1,"EndQualifierUnit":"Months","Volcano":"Akutan","ParentVolcano":"Akutan","VolcanoID":"ak6","ParentVolcanoID":"ak6"},{"ID":632,"Name":"Wrangell 2007/2","Description":"   From McGimsey and others, 2011: \"On January 13, 2007, at 0423 UTC (1923 AKST January 12), a M8.2 earthquake in the Kurile Islands likely triggered seismicity at several Alaska volcanoes including Wrangell, Katmai, and possibly Korovin, as the low frequency, large magnitude wavetrain rolled through these areas (Stephanie Prejean, AVO/USGS, written commun., 2007). There were no reports of anomalous steaming at Wrangell immediately following this event; however, on February 7, a fairly large local earthquake was recorded on the Wrangell network (Katrina Jacobs, AVO/UAFGI, written commun., 2007), that was followed 2 weeks later by reports of steaming from the summit. The report came from staff at Wrangell-St. Elias National Park and Preserve in Copper Center, and was presented during a local newscast (KTUU 5 p.m. report, February 20, 2007). This was the first report of Wrangell steaming in several years. \r\n   \"Local residents reported more episodes of steaming in March [see figs. 4 and 5 in original text]. On the evening of March 25, a strong sulfur odor was reported by a resident living about 50 air miles north of the summit of Wrangell, who also stated that this occurrence was rare in his 15 years living in the area. Earlier in the day, several multi-station seismic events were recorded on the Wrangell network (Katrina Jacobs, AVO/UAFGI, written commun., 2007). A few months later local residents sent AVO photographs taken on June 20 of steaming from Wrangell and a deposit of ash extending from the west crater several thousand feet down the southwest flank [see fig. 6 in original text]. This ash was likely redistributed from the summit craters by strong winds. No anomalous seismic activity was observed.\"","StartYear":2007,"StartMonth":2,"StartDay":7,"StartTime":null,"StartQualifier":1,"StartQualifierUnit":"Months","EndYear":2007,"EndMonth":6,"EndDay":20,"EndTime":null,"EndQualifier":3,"EndQualifierUnit":"Minutes","Volcano":"Wrangell","ParentVolcano":"Wrangell","VolcanoID":"ak326","ParentVolcanoID":"ak326"},{"ID":590,"Name":"Cleveland 2007/6","Description":"    Although intermittent thermal anomalies were sporadically observed in satellite images by AVO throughout 2007, on June 12, steam emissions caused a plume that extended 200 km from the volcano, and pilots reported the height as up to 12,000 feet (3650 m).  Significant thermal anomalies were observed in satellite images on June 17 and 26, and AVO geoscientist interpret these as being suggestive of low-level eruptive activity.  Weaker thermal anomalies were observed on July 3, 5, and 12.  \r\n   On July 20, 2007, an intense thermal anomaly and associated steam/gas plume were observed at Cleveland in satellite images, prompting AVO to raise the aviation color code from YELLOW to ORANGE, and the volcano alert level to WATCH.  AVO later received photographs of the event, showing small bursts of ash rising a few thousand feet above the summit.  Persistent thermal anomalies were observed in satellite data for the following week.  During the first week in August, they were intermittently visible, and then occasionally visible.  Photographs taken on July 27 show fresh volcanic ejecta on Cleveland.\r\n   On Sunday, August 12, a pilot reported that Cleveland was not steaming and showed no signs of activity.  During the following two weeks, occasional thermal anomalies were observed in satellite imagery, despite the mostly cloudy conditions\r\n   On Thursday, September 6, 2007, AVO lowered the aviation color code to YELLOW, and the volcano alert level to ADVISORY, due to the decreased intensity of the thermal anomalies.\r\n   On October 12, AVO reported that retrospective analysis of seismic data indicated an explosion at Cleveland on October 3, 2007.  A thermal anomaly was detected on October 7.  \r\n   On November 20, AVO observed a weak thermal anomaly near the summit of Cleveland.\r\n   On January 17, 2008, a minor ash emission was detected in satellite data.  AVO estimates that the cloud height was likely less than 10,000 ft (3048 m).  A weak thermal anomaly was observed at the summit in several satellite images following the ash event.\r\n   A weak thermal anomaly was again detected in satellite imagery on January 30.  Although Cleveland was often obscured by clouds in early February, a break in clouds on the night of February 7 permitted a brief satellite view of a diffuse, low-level (5000 ft or less) ash plume that extended up to about 12 km southeast of the volcano.  On February 8, aircraft pilots reported seeing a plume from Cleveland up to 20,000 ft.  Satellite data from AVO showed a diffuse ash cloud extending northwest from the volcano.\r\n\r\nOn March 4, 2008, a pilor reported minor ash to 5,000 feet above sea level in the vicinity of Cleveland, and a weak thermal anomaly was observed the following day. Thermal anomalies continued throughout March and April, and a small, low-altitude (less than 15,000 feet) discrete ash cloud was observed in satellite images from May 7, 2008.\r\n\r\nOn Monday, July 21, 2008, fishing boats reported an eruption occurred at Cleveland at approximately 12:00 AKDT. AVO raised the color code/alert level to ORANGE and Watch. The eruption continued, with a persistent ash emission from 10,000 to 20,000 feet above sea level. Also on July 21, a strong thermal anomaly was observed in satellite images, perhaps indicative of a lava flow. By August 6, the thermal anomalies had decreased in intensity, indicating that hot flows erupted onto the upper west, south, and southeast flanks had slowed. At that time, the last ash plume observation (satellite imagery) was July 29, although visibility is often limited. AVO lowered the color code/alert level to YELLOW and Advisory on August 6. \r\nDue to increasing thermal anomalies, AVO again raised the level of concern color code and alert level ot ORANGE and Watch on August 10, 2008. A small ash plume to 25,000 feet was observed on August 12. Eruptive activity declined, and the color code/alert level was lowered to YELLOW and Advisory on August 25.\r\n   A thermal anomaly was last noted on September 4, 2008, and AVO lowered the color code/alert level to Unassigned/Unassigned on October 9, 2008.\r\n\r\nFrom McGimsey and others (2011): \"Cleveland began 2007 in Aviation Color Code YELLOW and Volcano Alert Level ADVISORY following intermittent eruptive activity throughout 2006 (Neal and others, 2008b). Discussions in weekly AVO staff meetings, during January and early February 2007, on downgrading Cleveland to Aviation Color Code GREEN were interrupted by the detection of new thermal anomalies [see table 5 in original text]. Satellite data from February revealed evidence of recent activity involving ejection of bombs and debris on the upper flanks and generation of water-rich flows that travelled halfway to the coast. No ash emissions or ash fall deposits were observed. This level of activity -accompanied by persistent thermal anomalies - occurred throughout the spring and early summer. On July 20, an intense thermal anomaly (fig. 40) was accompanied by a steam and gas plume visible in satellite images [see fig. 41 in original text], and mariners in the area reported low-level ash emissions [see fig. 42 in original text]. Several small SO2 plumes were detected in Ozone Monitoring Instrument (OMI) satellite data (Dave Schneider, AVO/USGS, written commun., 2010). The ash and SO2 emissions signaled an increase in eruptive activity prompting AVO to raise the Aviation Color Code and Volcano Alert Level to ORANGE/WARNING.\r\n   \"Over the next 3 weeks, thermal anomalies were observed when weather conditions allowed for clear views, but no steam or ash emissions were observed. A pilot got a close view of the summit crater on July 27 and reported evidence of recently emplaced debris including blocks rimming the crater and sulfur deposition [see fig. 43 in original text].\r\n   \"A new Web camera aimed at Cleveland was installed in Nikolski, 75 km (45 mi) to the east, on August 6, but poor weather frequently precluded imaging the volcano. During the last 2 weeks of August, thermal anomalies decreased in size and intensity. The Aviation Color Code and Volcano Alert Levels were downgraded to YELLOW/WATCH on September 6 in response to the apparent waning of eruptive activity. Thermal anomalies continued to be observed, but with lower temperatures and intensities [see fig. 44 in original text].\r\n   \"Retrospective analysis of seismic data from stations located on Umnak Island, and distant pressure sensors [see table 5 in original text], suggested that an explosion occurred at Cleveland on October 3, 2007. No other evidence of this activity was forthcoming. Thermal anomalies continued to be seen through mid-November, visible during the few non-cloudy satellite views. During late November and through December, no thermal anomalies or activity were reported, and Cleveland ended 2007 in Aviation Color Code/Volcano Alert Level YELLOW/ADVISORY.\r\n   \"As in 2006, AVO tracked and responded to Cleveland activity in 2007 by relying heavily on remote sensing of the volcano and rapid response to reports received from pilots or other sources. Automatic PUFF runs of hypothetical ash trajectories appeared on the PUFF Website.\"\r\nFrom Neal and others (2011): \"Cleveland volcano on remote Chuginadak Island in the central Aleutians continued to produce infrequent but sudden explosions of ash in 2008 with a brief period of more vigorous activity in late July. Cleveland is unmonitored by ground-based seismic instrumentation. A web camera 73 km (45 mi) east in the community of Nikolski on Umnak Island is often obscured by weather. In an area of frequent thick cloud cover, satellite remote sensing is limited in application to reliably detect thermal anomalies and ash clouds resulting from volcanic explosions.\r\n   \"Cleveland volcano began 2008 at Aviation Color Code YELLOW and Volcano Alert Level ADVISORY. Daily satellite monitoring detected an ash cloud drifting north from Cleveland in imagery on January 17; the cloud rose less than about 3 km (10,000 ft) ASL and it was visible in satellite imagery for 2 hours before dissipating. A weak thermal anomaly (TA) persisted in the summit area following this event, visible to analysts in rare, clear satellite images over the next few weeks. Another low-level (below about 1.5 km or 5,000 ft ASL) ash cloud was visible in a satellite image on February 8. Later that day, two pilot reports of volcanic ash from Cleveland reaching altitudes of 20,000 ft (6,100 m) ASL, confirmed on satellite imagery, prompted AVO to elevate the volcano to ORANGE/WATCH. With the exception of a weak, possible TA several days later, no further activity was detected and Cleveland was returned to YELLOW/ADVISORY status on February 12.\r\n   \"Minor, short-lived ash explosions continued through the winter and were caught by the twice-daily routine satellite monitoring by AVO analysts or pilots on February 16, February 22, February 29, and March 4. Weak Tas seen in satellite imagery often followed these ash bursts; Tas continued to be spotted into the spring. ASTER satellite data in mid-April indicated intermittent low level activity producing ejecta and flowage deposits of very limited extent [fig. 28; imageid 14231].\r\n   \"In late April and early May, the TA at Cleveland became more persistent. On May 7, an ash cloud was detected in satellite imagery and AVO received a report from the F/V Raven Bay of a dusting of ash north of the community of Nikolski. Satellite imagery detected impact craters in snow near the summit of the volcano, consistent with an explosive event. A weak TA was detected on June 8.\r\n   \"No further reports of activity were received until July 21 when fishing vessels reported an explosive eruption of Cleveland about 12 p.m. Several mariners documented activity with photographs and video [figs. 29; imageid 15336, 30; imageid 15097 and 31; imageid 15373]. The ash cloud was described as moving generally northwest from the volcano but the cloud was not visible in satellite imagery, perhaps due to thick regional cloud cover. AVO declared ORANGE/WATCH based on these reports. Subsequently, pilots reported the Cleveland ash plume to be between 15,000 and 17,000 ft ASL and moving southeast from Cleveland. An AVO scientist aloft over Okmok in a USCG C-130 also observed the Cleveland ash cloud - distinctly darker than the regional meteorological clouds - approaching from the west.\r\n   \"On July 22, satellite imagery showed a greater than 50 km (31 mi) long plume of gas and water vapor with some ash drifting east and southeast at an altitude of between 3 and 6 km (10,000 and 20,000 ft). A strong and persistent TA may have reflected the presence of a lava flow in the summit crater and along the upper steep portion of the volcano. A fairly continuous, weak ash plume continued at least through July 25. On July 27, satellite images showed a possible ash cloud drifting southeast with a cloud top of less than 6 km (20,000 ft). The strong TA near the summit of the volcano decreased in intensity during the first week of August and on August 6, AVO downgraded Cleveland to YELLOW/ADVISORY.\r\n   \"On August 11, AVO reinstated ORANGE/WATCH because of the persistent TA interpreted to reflect effusion of lava from the summit crater. An August 12 satellite image showed a small ash cloud rising to about 25,000 ft (7,600 m) ASL and drifting southwest about 60 mi (100 km) before dissipating. Despite an intermittent thermal anomaly, AVO detected no further ash emissions and downgraded the volcano to YELLOW/ADVISORY on August 25 and to UNASSIGNED on October 9. (Note: in prior year reports, AVO has used the term 'Not Assigned' for this status).\r\n   \"The volcano was relatively quiet until October 28 when an ash cloud rising to about 15,000 ft (4,600 m) ASL and drifting east was spotted in satellite imagery. On October 29, another cloud was 100 mi (160 km) long and drifting northeast at 10,000 ft (3,050 m) with little or no ash observed. A strong TA over the summit of the volcano was noted on October 30, but given the low-level nature of the recent activity, AVO did not elevate the Color Code or Alert Level.\r\n   \"On December 24, after a persistent TA near the summit, AVO returned to YELLOW/ADVISORY based on the observation that ash emission events often follow a protracted and strong thermal signal. About 1 week later, on January 2, 2009, Cleveland produced a short-lived ash burst to an estimated 20,000 ft (6,000 m) ASL.\"\r\nOn December 23, 2008,  AVO noted a persistent thermal anomaly at Cleveland and raised the volcanic alert level and the aviation color code to Advisory/Yellow on December 24. Clouds obscured satellite views of Cleveland until December 28, when a clear view showed that the December 23 anomaly persisted. \r\nFrom McGimsey and others (2014): \"On January 2, 2009, a brief but explosive ash emission was detected in satellite images. The plume was visible in satellite images for several hours, rose to about 20,000 ft (6 km), and drifted east-southeast up to 240 km (150 mi) downwind dispersing harmlessly over the North Pacific. Flowage deposits draped the flanks with the two largest flows (about 100 m wide; 328 ft) extending down the northeastern and northwestern flanks for at least 2 km (1.2 mi). The eruption produced airwaves that registered on seismometers on adjacent Umnak and Unalaska Islands, as well as on a pressure sensor at Shishaldin Volcano on Unimak Island. Similar airwaves were observed from the November 3, 2008 eruption of Cleveland (M. Haney, AVO/USGS, written commun., 2009, AVO internal log entry). \r\n\"No further activity was noted until the end of January when satellite images showed evidence of recent eruptive activity visible around the summit of Cleveland. Retrspective analysis on January 23 of prior satellite data indicated that a short-lived, low-level ash emission may have occurred early on the morning of January 21.\"","StartYear":2007,"StartMonth":6,"StartDay":null,"StartTime":null,"StartQualifier":1,"StartQualifierUnit":"Months","EndYear":2009,"EndMonth":1,"EndDay":21,"EndTime":null,"EndQualifier":2,"EndQualifierUnit":"Days","Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":589,"Name":"Pavlof 2007/8","Description":"   From McGimsey and others, (2011): \"Pavlof, one of the most frequently active volcanoes in the Aleutian arc, abruptly erupted on August 14, 2007, following an 11-year repose [see fig. 25 in original text]. The 31-day Strombolian eruption was preceded by less than 1 day of increased seismicity detected on the AVO seismic network, and produced a spatter-fed lava flow, minor ash clouds, and lahars that extended down the south flank into the sea. The following account is drawn in part from Waythomas and others (2008).\r\n   \"The previous eruption of Pavlof Volcano was September 1996-January 1997 (Neal and others, 1997; McGimsey and Wallace, 1999). Minor activity (snowmelt, ash dustings, steam plumes, sulfur emissions) was noted in 1999 and 2001, and in 2005, steaming was observed at adjacent Hague volcano [see table 4b in original text]. Nothing unusual was observed during the summer of 2007 and the seismicity was at background levels through August 13. Abruptly on the morning of August 14, the 5-station seismic network on Pavlof began recording low-frequency earthquakes occurring at a rate of 2 to 7 events every 10 minutes, a pattern that had preceded eruptions in 1996, 1986, 1983, and 1981 (McNutt, 1987; McNutt, 1989; Roach and others, 2001). Although NWS observers in Cold Bay (37 mi southwest) with clear views of the volcano could see no anomalous steaming or other activity, and clear satellite views of the summit that morning also showed no signs of activity, the dramatic increase in seismicity prompted AVO to raise the Aviation Color Code/Volcano Alert Level to YELLOW/ADVISORY.\r\n   \"During the night, an intense thermal anomaly (TA) was visible in satellite images (Advanced Very High Resolution Radiometer-AVHRR), and seismic activity continued to increase in both number and duration of events per hour, clear signs that the unrest was escalating. On the morning of August 15, based on observations of the TA and increasing seismicity, AVO elevated the Aviation Color Code/Volcano Alert Level to ORANGE/WATCH and announced that an eruption was expected. With the upgrade in color code, AVO began 24-hour surveillance of the volcano. Later in the day, AVO received eyewitness accounts from mariners of incandescent blocks rolling down the eastern-southeastern flank of the volcano during the previous night, beginning around midnight. Pilots reported a thin, low-level ash plume extending a few kilometers southwest from the summit. After receiving these reports, AVO established that the volcano was in eruption. Aerial photographs taken on August 15 show lava fountaining from a vent located about 200 m (650 ft) below the summit [see fig. 26 in original text].\r\n   \"On August 16, strong seismic signals recorded at a single station (PVV), located 8.5 km (5.3 mi) southeast of the summit, heralded the passage of lahars down the south flank; more than 41 lahar events would be recorded by this station over the next 29 days. Satellite observations of a strong thermal anomaly (TA) [see fig. 27 in original text] and nighttime incandescence at the summit reported by local residents were indications of vigorous lava eruption at the summit vent [see fig. 28 in original text]. The seismic network recorded long periods of volcanic tremor with repetitive explosions that indicated nearly continuous Strombolian eruption. In addition to the generation of lahars, this activity produced low-level ash clouds (5-6 km ASL; 3.1-3.7 mi), and a spatter-fed lava flow that descended the southeastern flank. By August 18, AVO personnel in the field reported that vigorous eruption of lava at the summit continued. Using a Forward Looking Infrared (FLIR) camera, they determined that a 20- to 50-m-wide, 65- to 165 ft-wide) 600 °C (1,112 °F) lava flow extended 565 m (1,850 ft) from the vent down the southeast flank [see figs. 29 and 30 in original text]. Thermal data collected the next day indicated that the outer part of this flow was about 140 °C (284 °F) and had cooled considerably. The vent crater for the last eruption of Pavlof, in 1996, was located on the upper northwestern side of the summit. For this eruption, the active vent migrated to the upper southeastern side, about 200 m (650 ft) below the summit [see figs. 31-33 in original text].\r\n   \"Seismicity at Pavlof was elevated and steady throughout the remainder of August and then began waxing and waning for the first week of September. A strong TA was present in satellite images, even through clouds, during this time. During the second week of September, the seismicity began showing signs of a steady decrease [see fig. 34 in original text], and by September 13, seismicity decreased to low levels and only a minor steam plume was visible above the volcano. A TA was last seen on September 15, and AVO declared that the activity had reached a lull by September 17. An AVO field crew with clear views reported that all eruptive activity had ceased during their visit on September 19, and the Aviation Color Code /Volcano Alert Level was downgraded to YELLOW/ADVISORY on September 20. The next 2 weeks of low seismicity and no further signs of activity or unrest prompted AVO to declare the eruption over (ending on September 13), and the Color Code/Volcano Alert Level was downgraded to GREEN/NORMAL on October 5.\r\n   \"Ash, a blocky lava flow, and multiple lahars were generated by this eruption. Mixed ash and steam clouds produced during the most energetic eruptive period, mid-August to mid-September, reached altitudes of 5-6 km (about 20,000 ft) ASL. The plumes were diffuse, drifted primarily to the southeast over the North Pacific Ocean, and many could not be detected in satellite imagery. No ash reportedly fell on nearby communities and there were no significant impacts to aviation. AVO deployed a DRUM aerosol impactor (particle collector) in Sand Point, 90 km (56 mi) east of Pavlof, and collected fine ash (2.5-0.1 µm). Although no visible ash fallout was observed during aerosol sampling, these results demonstrate that volcanic ash was present in respirable size fractions downwind of the volcano even during periods of low ash emissions (Peter Rinkleff and Cathy Cahill, AVO/UAFGI, written commun., 2010).\r\n   \"Analyzed samples from the lava flow are basaltic andesite in composition (53% SiO2), which is similar to the products of previous Pavlof eruptions (McNutt and others, 1991; Neal and McGimsey, 1997). Lahars were produced by interaction of hot blocks and spatter from the lava flow with snow and ice on the southeastern flank. The lahars inundated an area over 2 km2 (0.78 mi2) and formed a debris fan that extended 3.6 km (2.2 mi) from the base of the volcano into Pavlof Bay [see fig. 35 in original text].\"","StartYear":2007,"StartMonth":8,"StartDay":15,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2007,"EndMonth":9,"EndDay":13,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Pavlof","ParentVolcano":"Pavlof","VolcanoID":"ak210","ParentVolcanoID":"ak210"},{"ID":652,"Name":"Aniakchak 2008/3","Description":"Seismometers at Aniakchak Volcano appeared to record anomalous seismicty at Aniakchak during the spring of 2008. Further analysis revealed that the signals were a product of icing on the seismometers, and not of volcanic origin.\r\nFrom Neal and others (2011): \"AVO seismic analysts noted a swarm of seismic events at Aniakchak during routine seismic checks of Alaskan volcanoes on March 8. The activity continued intermittently over the next week with events occurring as frequently as 5-10 per hour. Interpreting the significance of the signals was hampered by the fact that only a single station in the Aniakchak network, ANNW, was operating at the time. AVO increased seismic watch frequency for Aniakchak in response and contemplated organizing a winter-time field visit to restore more of the seismic network.\r\n   \"Subsequently, an evaluation of historical seismicity at Aniakchak during times of more complete network operation suggested that the anomalous signals were likely weather-related (Katrina Jacobs, AVO/UAFGI, written commun., 2008). Similar swarms had occurred on a number of occasions between 2005 and 2008, but none were typical multi-station volcanic events and all showed a strong correlation with time of day. Years of maintenance efforts at the Aniakchak network documented a strong vulnerability of sites to heavy icing that could have been responsible for the intermittent seismic signals. Based on this, an AVO field response was canceled.\"","StartYear":2008,"StartMonth":3,"StartDay":8,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2008,"EndMonth":3,"EndDay":14,"EndTime":null,"EndQualifier":2,"EndQualifierUnit":"Days","Volcano":"Aniakchak","ParentVolcano":"Aniakchak","VolcanoID":"ak14","ParentVolcanoID":"ak14"},{"ID":672,"Name":"Shishaldin 2008/6","Description":"From Neal and others (2011): \"On June 3, AVO received a pilot report of a steam plume rising about 2,000 ft (610 m) above the summit. On July 27, AVO was contacted by a mariner from the fishing vessel Castle Cape who reported Shishaldin 'puffing' on July 26 between about 8 p.m. and 12 a.m. local time. He described ash falling from the dissipating puffs. For all of these reports, there were no unequivocal correlative changes in seismicity, nor did any ash signal or thermal anomaly appear in satellite images. On July 29, AVO staff flying by Shishaldin from Dutch Harbor en route to Anchorage noted a faint wisp of vapor from the summit crater; there was a hint of dark discoloration high on the east flank, but views were quite distant. AVO received images of the volcano from a NOAA scientist on July 30 and several additional pilot reports of a steam plume from Shishaldin arrived on August 3. It is possible that this spike in reports reflected increased vigilance on the part of pilots and others traveling in the Aleutians in the wake of the highly explosive and continuing eruption of Okmok Volcano about 300 km (190 mi) west of Shishaldin. Shishaldin also is easily visible from the air on approach into Dutch Harbor.\r\n   \"AVO staff and colleagues from the Plate Boundary Observatory field team conducted instrument maintenance, installed 13 GPS stations, a broadband seismometer, 6 borehole tiltmeters, and a web camera, and relocated 4 seismic stations on Unimak Island from July 30 to August 22, 2008. They noted no obvious evidence of recent ash fall on the surface although they did observe some discoloration of the upper ice and snow cover, along with typical, weak fumarolic emission from the summit crater [figs. 10; imageid 15239, and 11; imageid 31882].\"","StartYear":2008,"StartMonth":6,"StartDay":3,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2008,"EndMonth":8,"EndDay":3,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Shishaldin","ParentVolcano":"Shishaldin","VolcanoID":"ak252","ParentVolcanoID":"ak252"},{"ID":604,"Name":"Ahmanilix 2008/7","Description":"From Neal and others (2011): \"Okmok Volcano, a 10-km (6.2-mi) diameter Holocene caldera system in the central Aleutians [fig. 14; imageid 13283], began a protracted explosive eruption on July 12. The opening explosions consumed a portion of intracaldera Cone D within the east-central sector of the caldera, reaming several new craters into the caldera floor. Eruptive activity began only a few hours after a subtle increase in the rate of earthquakes followed by a short swarm sequence, both noted only in retrospect. Over the next 5 weeks, several hundred million cubic meters of tephra and lahar deposits blanketed much of northeast Umnak Island. Within the caldera, nearly continuous hydrovolcanic explosions accumulated many tens of meters of wet, mostly fine-grained tephra. Explosive activity completely disrupted existing groundwater and standing water bodies within the caldera, formed new lakes, and constructed a new tephra cone about 100-200 m (330-660 ft) high. This eruption was the first dominantly phreatomagmatic volcanic event in the United States since the Ukinrek Maars eruption in 1977. The following summary is taken largely from Larsen and others (2009).\r\n   \"Other than the seismicity recognized in hindsight, AVO noted no clear signs of precursory unrest at Okmok prior to the eruption onset. In fact, during the 2 months prior to July 12, Okmok produced only three earthquakes and no tremor episodes (intermittent tremor episodes had been recorded since the seismic network was installed in 2003 and had continued into mid-2005; Reyes and McNutt, 2008). Campaign and continuous GPS data had recorded nearly continuous inflation from 1997 to 2005, quiescence between 2005 and 2007, and notable (but not unprecedented) inflation in early 2008. Pre-eruptive displacements measured by GPS and InSAR indicated inflation of a pressure source about 2.6-3.2 km (1.6-2.0 mi) below sea level and underneath the approximate center of the caldera (Lu and others, 2005; Fournier and others, 2009).\r\n   \"AVO was first notified of the eruption by the USCG who had been contacted by the caretaker of Bering Pacific Ranch at Fort Glenn [Fort Glenn is a former U.S. Army base that now houses a cattle ranch operation about 10 km (6.2 mi) southeast of the caldera rim]. The caretaker and his family reported wet volcanic ash falling as they were evacuating the island first by helicopter and later by boat. An immediate check of Okmok seismicity by the AVO duty scientist confirmed that an eruption was in progress. AVO issued a notice of the eruption declaring Aviation Color Code RED and Volcano Alert Level WARNING and commenced 24-hour operations to respond to the event.\r\n   \"In addition to 24-hour staffing of the operations room in Anchorage, AVO mounted two helicopter-supported field responses to the eruption. The first operated from Unalaska between July 29 and August 5 and the second was based at Fort Glenn over a week in mid-September about 3 weeks after the eruption had ended. AVO received photographs taken by Fort Glenn ranch caretaker Lonnie Kennedy on several occasions. These photographs along with images from commercial and USCG aircraft, satellite imagery, and mariner accounts provided critical visual documentation of the eruption through time.\r\n   \"The most energetic phase of the eruption occurred over the first 10 hours of activity on July 12. The first satellite images of the ash plume were geostationary operational environmental satellite (GOES) images starting at 20:00 UTC on July 12. By 22:12 UTC, the ash cloud extended east over much of Unalaska Island [fig. 15; imageid 14279]. Both geometric image analysis of GOES and comparison of cloud motion with the PUFF ash dispersion model indicated a maximum initial column height of approximately 16 km (52,000 ft) ASL. Photographs of the eruption column by crews of a USCG C-130 and an Alaska Airlines jet taken about 5-6 hours into the eruption show a vertical, gray, ash-rich column rising into meteorological cloud layers; the top of the eruption plume appeared white and was estimated visually to be 30,000-35,000 ft (9,100 m-10,700 m) ASL. The ground was obscured and the aircraft too distant to make out any detail at the base of the eruption column.\r\n   \"The opening explosions and heavy tephra fall destroyed or disabled several AVO seismometers and continuously recording GPS instruments, however the remaining network density was sufficient to track the eruption. From July 13 through the end of the month, seismicity varied but remained well below the intensity of the opening eruption sequence on July 12. Eruption columns and clouds seen in satellite imagery and by passing aircraft varied significantly in altitude although these changes were not often in phase with recorded seismic amplitude (Larsen and others, 2009; table 5 in Neal and others 2011). Characteristics of most eruption clouds implicated the continuous involvement of water in the eruption process. On July 13, a Moderate Resolution Imaging Spectroradiometer (MODIS) satellite image showed two plumes -- one dark and ash rich and the other light in color and inferred to be very rich in water vapor -- emanating from the eastern portion of the caldera floor. Between July 13 and 21, photographs from Alaska Airlines and aerial observations by AVO staff from a USCG plane showed a light-colored plume with a wide base and multiple potential sources of ash explosions [fig. 16; imageid 14436].\r\n   \"Evacuated Fort Glenn ranch caretaker Lonnie Kennedy returned to the island on July 23 and, over the next several days, photographed eruption impacts and continuing ash emission and ash fall in the vicinity of the caldera. Kennedy documented ongoing muddy water flow across the lowlands surrounding the ranch; lahars in several drainages north of the ranch had been sufficiently energetic to destroy pre-existing wooden bridges and culverts and cause severe bank erosion. Dramatic new deltas had formed at the mouths of a number of creeks draining the northeast and southeast flanks of Okmok [fig. 17; imageid 15446]. The exact timing of lahar activity during the first days of the Okmok eruption is uncertain. It is also not clear if lahar formation was due to rain-remobilization of tephra, syn-eruptive condensation of water vapor entrained in the eruption cloud (W. Scott, USGS, written commun., 2008), dewatering of wet tephra fall, melting of snowpack, or some combination of these or other processes. Overbank deposits and the presence of large boulders atop the surface of the 2008 lahar fan at the mouth of Crater Creek (Crater Creek drains the caldera northwestward into the Bering Sea) suggest temporarily high discharge rates possibly caused by a sudden release of water from the caldera early in the eruption.\r\n   \"Kennedy's aerial photographs of the caldera from August 1 show the upper Crater containing an active, braided channel of muddy water indicating some drainage from the caldera. The terrain immediately east of the caldera was thickly covered in light brown to gray tephra. Deep rills and dendritic drainage networks existed on most surfaces; at higher elevations, the pre-eruption snowpack was visible beneath the 2008 debris, and water flowed from the base of the snowpack in many places. A partially clear view into the caldera on August 1 showed ash and water-vapor-rich clouds boiling from at least two point sources on the northwest flank of Cone D and just to the west of Cone D [fig. 18; imageid 15666]. Dark collars of debris enclosed each locus of venting. The pre-eruption lake northeast of Cone D had been significantly modified: standing water covered a much smaller area and what had been the lake was now a surface of tephra and scattered ponds.\r\n   \"The first AVO crew on scene in late July was unable to land near the caldera due to active ash emission. They focused on documenting the extent and character of ash fall and lahar deposits outside the caldera, taking observations of the ongoing eruption, repairing a key data repeater site on Makushin Volcano on Unalaska Island, and collecting samples and eye-witness accounts. They obtained some close-up views into the caldera and also distant views of the eruption column from the Fort Glenn ranch. On August 2 and 3, the eruption column had increased in intensity, height, and ash content [figs. 19; imageid 14700 and 20; imageid 14718]. This change was coincident with an increase in amplitude of seismic tremor. AVO crew observations, photographs, and film footage during this time of heightened activity suggest a migration of the location of active venting on the caldera floor over the span of minutes. On overflights near the eruption site, the field crew observed a ground-hugging cloud of tan-colored ash covering the caldera floor and obscuring views of the immediate area. In glimpses of the caldera floor near the site of the pre-eruption lake near Cone D, they noted chaotic, disrupted terrain and channels of flowing water.\r\n   \"Due to the renewed intensity of the eruption, AVO elevated the Aviation Color Code and Volcano Alert Level again to RED/WARNING early on the morning of August 2 [see table 5 in original text], and the caretaker and family at the Fort Glenn ranch decided to evacuate for the second time. During the last days of July and the first days of August, prevailing winds shifted to be out of the northeast.\r\n   \"Subsequently, over the first 2 weeks of August, eruption intensity and cloud height generally decreased and ash emission ceased altogether by August 19. A USGS helicopter crew working in the Aleutians entered the caldera on August 13 during the waning phase of eruption and photographed a single active vent enclosed within a steep-sided tephra cone [figs. 21; imageid 15120 and 22; imageid 15119]. Dark ash boiled out of the tephra cone surrounded by a collar of white water vapor; winds were from the northwest sending the ash and water vapor cloud over the summit of Cone D and the caldera rim. A significant lake was now present near the site of the pre-eruption lake and the landscape was completely covered with dark gray ash. The surface north of Cone D was pocked with craters several meters to several tens of meters in diameter. A series of scallop-margined basins and coalesced craters, some hosting standing water, extended in a line west of Cone D.\r\n   \"On August 23, about 1 week after the end of the eruption, Lonnie Kennedy again photographed the eastern caldera from the air. Although Crater Creek was open and flowing just inside the caldera, a through-going surface connection between Crater Creek and the growing lakes had not been established. Wind re-suspended a tan-colored ash in the vicinity of the largest of the new vents.\r\n   \"AVO's week-long September expedition to Okmok gathered reconnaissance information about the eruption deposits and impacts, repaired some seismic and GPS instruments, and deployed additional GPS recording stations (some of which were retrieved in the summer of 2009 by the Plate Boundary Observatory field crew). Most tephra sections excavated within and outside the caldera exposed planar to slightly wavy-bedded, fine-grained fall and surge deposits. Northeast of the vent region where tephra accumulation was thickest, the basal unit from the July 12 opening phase was a coarse ash-lapilli fall deposit; individual clasts were coated with a very fine ash [fig. 23; imageid 31902]. Evidence of significant water interaction throughout the 2008 tephra sequence includes (1) very high porosity of individual beds reflecting post-emplacement de-watering; (2) plastering texture on perpendicular surfaces facing the vent; (3) abundant accretionary lapilli; (4) overall fine-grained nature of the deposit. Outside the caldera, excavated sections contained mostly fall deposits with thin and discontinuous aeolian horizons; no clear evidence for energetic, far-traveled, extra-caldera surges was noted.\r\n   \"Field observations in September combined with analysis of photographs and satellite images indicate that the eruption occurred from a series of vents that opened during the first 2 weeks of the eruption. These vents extended in a roughly linear zone about 2 km (1.2 mi) long across the caldera floor [figs. 24; imageid 15480 and 25; iin original text]. One crater formed next to, and eventually captured and drained, the pre-existing lake northeast of Cone D. A tephra cone ('New Cone') had been constructed atop the longest-lived 2008 vent [fig. 26; imageid 15476]. By mid-September, the explosion and collapse craters to the west of Cone D had filled with water and formed a new lake ('New Lake') about 0.6 km2 (0.2 mi2) in area [figs. 24; imageid 15480 and 25; in original text].\r\n   \"Eruptive products from the 2008 sequence are basaltic andesite in composition, slightly more silicic than the range of Okmok chemistry represented by other post-caldera (last about 2,000 years BP) eruptions (Larsen and others, 2009). The fine-grained nature of most 2008 tephra and the lack of an effusive phase pose a challenge to understanding changes in eruption chemistry with time. Coarse juvenile lapilli from the opening phase of the 2008 eruption were collected on the caldera rim just above the outlet of Crater Creek in a notch through the caldera wall informally called 'The Gates' [fig. 14; imageid 13283]; this location was near the main northeast axis of deposition. Clast types in the July 12 opening tephra range from dense to vesicular scoria and pumice, and crystal fragments (Mariah Tilman, AVO/UAFGI, written commun., 2008). Some dense clasts may represent accidental lithics incorporated during the opening explosions through the caldera floor and lava flows of Cone D. Larger frothy pumiceous clasts were found along the shoreline of one of the shallow lakes within the caldera; because they are not in place, they cannot be confidently assigned to the 2008 event, but they were fresh-looking, fragile, and most likely represent material erupted on July 12. These clasts are up to 5-10 cm (2-4 in.) across and are light to dark brown, vesicular, scoriaceous pumice with irregular, fractured chill rinds.\r\n   \"Following cessation of eruption in mid-August, seismicity remained relatively low with occasional bursts of higher amplitude tremor. AVO downgraded the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY on August 27 [see table in original text] after a week with no ash clouds discerned in satellite images. Occasional thermal anomalies were visible by satellite and are likely attributable to the still-warm vent area, fumaroles, and/or lakes within the caldera. By mid-November, after 3 months of steadily decreasing seismicity, AVO changed the Aviation Color Code to GREEN and Volcanic Alert Level to NORMAL. In the accompanying remarks, AVO indicated that despite the cessation of eruptive activity, hazardous conditions persisted. Unstable, muddy surfaces and slopes of new volcanic debris within the caldera could collapse at any time. New and rapidly changing lakes, ponds, and multiple steep-walled craters through the new tephra blanket would present a hazard to anyone visiting the caldera. Magmatic gases and areas of high temperature could persist around the new tephra cone. All drainages leading downslope from the rim of the caldera are susceptible to remobilization of ash and other loose debris during heavy rains and spring melt. The Crater Creek drainage on the north-northeast flank of Okmok was considered especially vulnerable to sudden flooding events if tephra dams within the caldera were to fail suddenly and release impounded water.\r\n   \"AVO maintained 24-hour staffing from July 12 through August 28. Over the course of the eruption, AVO issued 17 Volcanic Activity Notices and two Information Statements.\r\n   \"Eruption impacts were modest except for the significant disruption to the ranch caretaker family on Umnak Island who evacuated twice from the island including the first time under great duress during the most energetic phase at the start of the eruption. Primitive roads on the east and south flanks of the caldera were cut by lahars and water floods and rendered at least temporarily impassable. Ash accumulation suppressed grass growth that resulted in diminished over-winter feed for the livestock that roam the island. According to the Kennedy family, it is possible that an increased number of cattle perished in the winter of 2008-09 because of this (Susan Kennedy, written commun., 2009). The island also hosts a large number of caribou, although we are unaware of any systematic population counts to gauge the impacts of the eruption. Offshore Umnak Island, volcanic sediment delivered to the coastline built significant new lahar deltas and fishermen reported dramatic changes to bottom conditions in the weeks after the eruption (Lonnie Kennedy, oral commun., 2008) Several boats received minor to trace ash fall with no ill-effects reported other than a single collapsed air filter (Dustin Dickerson, oral commun., 2008). Out of concern for the effects of ash fall, the U.S.Coast Guard closed Umnak Pass for several days in the immediate aftermath of July 12.\r\n   \"Over the course of the eruption, trace amounts of ash fell on several occasions in Unalaska-Dutch Harbor 120 km (75 mi) northeast of the volcano. The airport closed briefly to allow for clean-up of the runway and taxi ways. Cannery workers and other residents were concerned about impacts of the ash fall, however slight, on their health, and AVO worked with local health care providers and cannery management, and with the Alaska Department of Environmental Conservation Air Quality Division to issue health related information. AVO and UAFGI staff installed a 3 stage DRUM impactor air sampler in Unalaska to sample volcanic particulate from the ash fall events (Peter Rinkleff, AVO/UAFGI, written commun., 2008). AVO staff also traveled to Unalaska in late July to meet with the local Director of Public Safety, the resident Department of Environmental Conservation employee, U.S. Coast Guard Station Chief, Native Health clinic supervisor, cannery management, contract weather observer, and airport supervisor and maintenance manager about their concerns and accounts of the eruption. AVO staff participated in local radio interviews, gave a public lecture on the eruption, and met with members of the community to gather eyewitness accounts and answer questions.\r\n   \"AVO received both ash and pumice samples from citizens in Unalaska. By July 24, some Unalaska residents reported pea to gravel sized light to dark brown pumice washing ashore on several beaches in Unalaska; based on the timing and physical characteristics of the clasts, it is possible that these represented marine transported pumice from the July 12 eruption onset. Whether pumice of this size fell at sea or was washed into the sea by lahars or other flowage processes on Umnak is unknown.\r\n   \"Flights across the North Pacific were impacted for a period of several days in mid-July as the July 12 eruption cloud drifted north and east over the Gulf of Alaska. During the week following the eruption, aircraft over the lower 48 States observed and photographed the remnant of the Okmok aerosol cloud as it transited across North America at elevations in excess of 30,000 ft (9,100 m) ASL. NWS maintained a nearly constant SIGMET for the area impacted by ongoing ash production during the event; SIGMET boundaries were modified over time on the basis of pilot reports of ash cloud drift as well as satellite images showing the cloud combined with forecast motion.\"","StartYear":2008,"StartMonth":7,"StartDay":12,"StartTime":"11:43:00","StartQualifier":null,"StartQualifierUnit":null,"EndYear":2008,"EndMonth":8,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Ahmanilix","ParentVolcano":"Okmok","VolcanoID":"ak347","ParentVolcanoID":"ak206"},{"ID":605,"Name":"Kasatochi 2008/8","Description":"  From Waythomas and others, 2008: \"Kasatochi Volcano, a small, 3 km diameter, 300 m high, island volcano in the central Aleutian Islands of Alaska (52.1693 degrees N latitude, 175.5113 degrees W longitude) erupted violently on August 7, 2008 after an intense period of precursory seismic activity. Kasatochi has received little study by volcanologists and has had no confirmed historical eruptions; it is not monitored with seismic instruments on Kasatochi Island.  The island is part of the Alaska Maritime National Wildlife Refuge and has been a long-term study site for the US Fish and Wildlife Service (USFWS), which has annually deployed scientists to the island to monitor seabirds for 13 years.  \r\n   \"The 2008 eruption occurred less than a week after USFWS personnel on the island began feeling small tremors. On August 4, the USFWS contacted the Alaska Volcano Observatory (AVO) to report these observations. At the time, the reports of earthquake activity were considered normal, as the area has frequent, and sometimes large, earthquakes and an early analysis suggested that the activity did not appear volcanic in origin. By early evening August 6, it became clear that a significant volcanic earthquake swarm was occurring in the vicinity of Kasatochi Island and that the scientists on the island could be endangered should they remain at their camp. At about 7 PM AKDT, AVO issued a formal Volcanic Activity Notice stating that Kasatochi volcano had become restless and raised the aviation color code and volcano alert level to yellow/advisory. AVO also recommended that the scientists on the island be evacuated as soon as possible.\r\n   \"Strong seismicity continued throughout the evening and into the next day. At about 10:30 AM AKDT August 7, a magnitude 5.8 earthquake occurred within a few km of Kasatochi. Soon after this earthquake, seismic instruments on nearby Great Sitkin Volcano began recording periods of strong volcanic tremor usually indicative of fluid (magma, gas, or both) motion and often associated with eruptive activity. AVO responded by raising the volcano-alert notification to orange/watch at 1:57 PM AKDT, indicating that an eruption was possible. Just after 2 PM AKDT, satellite images confirmed an eruption of Kasatochi was in progress and AVO issued a Volcanic Activity Notice announcing an aviation color code and alert level of red/warning. Thankfully, a local fishing boat had safely evacuated the two scientists less than 30 minutes prior to the opening blast.\r\n   \"The eruption was characterized by three distinct explosions that were detected by the seismic network on Great Sitkin Volcano, at approximately 2:01 PM, 5:50 PM, and 8:35 PM AKDT. The first two events produced relatively ash-poor, but gas-charged, eruption clouds that reached 45,000 - 50,000 feet above sea level and apparently no or very little local ash fall. The third event generated an ash- and gas-rich plume that also rose to 45,000 - 50,000 feet and produced several inches of ash and lapilli fall over the ocean and on islands southwest of Kasatochi, including minor amounts on Adak Island, the closest island with a year-round population, about 50 miles from the volcano. Boats in the vicinity of the volcano reported 4-5 inches of coarse grained ash fall, darkening skies, and lightning, likely caused by static electricity in the ash plume.  The third event was followed by about 17 hours of continuous ash emission as determined from satellite data. The cumulative volcanic cloud from Kasatochi (\u003ca href=\"http://www.avo.alaska.edu/image.php?id=15049\"\u003eFig. 1\u003c/a\u003e) contained a large amount of sulfur dioxide gas that was detected by the Ozone Monitoring Instrument on NASA's EOS-Aura satellite for more than a week after the eruption as the cloud circled the globe. The ash and gas cloud drifted east and interfered with air travel between Alaska and the conterminous US causing at least 40 flight cancellations and stranding many thousands of travelers. The cloud was visible for thousands of miles downwind and apparently was the cause of some brilliant sunsets over the Midwestern US. \r\n   \"AVO and USFWS scientists visited Kasatochi Island on August 22 and 23. Photographs of what they found can be seen on the AVO web site (www.avo.alaska.edu). The visit confirmed that a major eruption had occurred, and thick deposits of gray volcaniclastic debris and ash now covered the formerly lush volcanic island that was home to over a hundred thousand seabirds (\u003ca href=\"http://www.avo.alaska.edu/image.php?id=16101\"\u003eFig. 2\u003c/a\u003e, \u003ca href=\"http://www.avo.alaska.edu/image.php?id=16102\"\u003e Fig. 3\u003c/a\u003e). Pyroclastic-flow deposits exposed along the new coastline, now about 400 m further into the sea were noticeably warm when visited on August 22 and 23 (\u003ca href=\"http://www.avo.alaska.edu/image.php?id=15306\"\u003eFig. 4\u003c/a\u003e). These deposits recorded significant collapse of the vertical eruption column to produce hot avalanches of rock debris, gas, and ash. The pyroclastic flows also initiated a small tsunami that was recorded by tide gages at Atka, Adak and Amchitka. Attempts to locate the USFWS camp were unsuccessful and the ca. 75-year-old cabin was either swept from the island or buried beneath the new deposits. A few thousand chicks of nesting seabirds had not yet left their nesting burrows or crevices and were most likely entombed under the ash. Few signs of life remained on the former major seabird colony. The summit crater had enlarged in diameter by about 100 m and the crater floor was steaming profusely from a number of circular vents and warm areas on the crater floor. \r\n   \"The 2008 eruption of Kastochi was a significant test of AVO's ability to assess the reawakening of a seismically unmonitored and little-studied, remote volcano. Fortunately, the earthquake activity was strong enough to be recorded on existing seismic networks on nearby volcanoes and scientists on the island were able to communicate with local contacts to coordinate a rescue. These seismic networks were installed with funding from the Federal Aviation Administration to reduce the hazard to aviation from volcanic ash. In this case, the instrumentation was crucial in recognizing the signs of significant unrest and potential for major eruptive activity, saving the lives of two biologists and providing the aviation community with advance warning of a possible eruption. AVO and its partner agencies in DOI now have a unique opportunity to evaluate the response of Kasatochi's ecosystem to a major volcanic event and to address how the landscape evolves following significant physical, chemical, and biological changes. \"\r\nFor a record of AVO's Information Statements and Weekly Updates during the eruption, please see  \u003ca target=\"_blank\"  href=\"http://www.avo.alaska.edu/activity/Kasatochi.php\"\u003ehttp://www.avo.alaska.edu/activity/Kasatochi.php\u003c/a\u003e.\r\n  For an account of the biologist's evaucation from Kasatochi, please see Rozell, 2010.\r\n\r\nFrom Neal and others (2011): \"Analyzed 2008 juvenile pumice clasts are crystal-rich andesite with plagioclase, orthopyroxene, clinopyroxene, hornblende, and Ti-magnetite phenocrysts in a clear glass matrix that also contains elongate plagioclase, pyroxene, and amphibole microlites. Preliminary petrology and melt inclusion work suggests pre-eruption storage at depths of about 6.5-12.5 km (4-8 mi) and rapid ascent to the surface (Izbekov, 2008; Izbekov and others, 2009). Gabbroic inclusions in Kasatochi pumice contained amphibole up to 11 cm (4 in.) in length (P. Izbekov, AVO/UAFGI and C. Nye, AVO/ADGGS written commun., 2010).\r\n   \"Biological impacts of the eruption were significant in the short term; quantifying impacts to plant and animal inhabitants and the nearby ecosystem is the subject of an ongoing interdisciplinary research program (Buchheit and Ford, 2008). Aviation impacts also were severe. The ash and aerosol cloud drifted east during the week following the eruption interfering with air travel between Alaska and the conterminous U.S., causing at least 40 flight cancellations, and stranding many thousands of travelers. At least one commercial jet aircraft flew through what the flight crew reported as a thin volcanic cloud layer prompting an inspection and precautionary replacement of some equipment. A second aircraft over Canada also reported entering a sulfurous, yellowish-brown haze layer (Guffanti and others, 2010). In both cases, no in-flight malfunctions were noted and there was no discernible damage or verifiable volcanic ash contamination upon inspection.\r\n   \"The eruption cloud was visible for thousands of miles downwind and was the cause of some brilliant sunsets over the Midwestern U.S. The SO2 cloud from this eruption was detected by the Ozone Monitoring Instrument on NASA’s EOS-Aura satellite as it circled the globe. A small tsunami [35 cm (14 in.) in amplitude] associated with the eruption was recorded by a tide gage at Adak, however, no damage was reported.\"","StartYear":2008,"StartMonth":8,"StartDay":7,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2008,"EndMonth":8,"EndDay":12,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Kasatochi","ParentVolcano":"Kasatochi","VolcanoID":"ak146","ParentVolcanoID":"ak146"},{"ID":761,"Name":"Shishaldin 2009/1","Description":"From McGimsey and others (2014): \"Shishaldin Volcano is one of the most active volcanoes of the Aleutian arc. Minor unrest and eruptive activity have been documented for all but a couple of the past 20 years. In 2008, Shishaldin maintained the pattern of producing steam plumes, occasionally with minor phreatic ash emissions (Neal and others, 2011). Thermal anomalies (TA) were observed on September 5 and December 18, 2008. This activity increased in early 2009 with the occurrence of a significant 2-pixel thermal anomaly and a slight increase in seismicity on January 5. AVO issued a VAN the following day upgrading the Aviation Color Code/Volcano Alert Level to YELLOW/ADVISORY. That day, pilots and ground observers reported a constant steam plume rising about 1,000 ft (about 300 m) above the summit and trailing of 16-25 km (10-15 mi) to the southeast. Satellite views on January 8 showed a steam-filled crater and no ash on the snow-covered flanks, and a pilot's photograph taken January 11 shows a pulsing steam plume. A few days later, on January 13, AVO seismologists identified low-amplitude, minor tremor in the seismicity at Shishaldin, which continued for several weeks and then apparently faded out.\r\n\"On January 17, the on-island Shishaldin Web camera, which had been out of service since October 22, 2008, was made operational again, although images were not recorded until February 20. Over the next couple of weeks, thermal anomalies were few, seismicity remained low, and although the reports of steaming continued, steam emissions from Shishaldin are considered normal. The return to background conditions prompted AVO to downgrade the Color Code/Alert Level to GREEN/NORMAL on February 11, 2009. A February 28 Web camera image shows a modest steam plume rising from the summit. Image quality problems with the Web camera in March and April led to the camera being taken off-line on April 30.\r\n\"Over the next 7 weeks, occasional thermal anomalies were observed along with continuous low-level tremor, which was not considered unusual activity for Shishaldin. Then, on April 7, a PenAir pilot reported Shishaldin streaming more vigorously than in the previous 16 months of observing during his weekly flights by the volcano. A thermal anomaly was reported in satellite imagery that day as well. Activity continued during the next couple of weeks, and on April 20, thermal activity at the summit spiked with the recording of multiple thermal anomalies having saturated pixels, indicative of high ground temperatures (more than 300C; about 600F). This level of thermal activity was last observed at Shishaldin during the run-up to the 1999 eruption (J. Dehn, AVO UAFGI, 2009 internal log entry 31659). A pilot reported steaming on May 5, and an observer on a different flight that day reported also seeing dark colored, linear features on the northern side of the summit. These would later be interpreted to be minor streams of 'dirty' water; no significant deposits were produced.\r\n\"Throughout June, thermal anomalies were detected on about one-third of the days, with a particular strong anomaly noted on June 9; no unusual seismicity was detected. A clustering of thermal anomalies appeared to coincide with favorable vertical view angles. On the night of June 25, an ASTER thermal infrared satellite image showed a thermal anomaly and a 22-km-long (14 mi) steam plume extending east-northeast from Shishaldin. Clouds blanketed most of Unimak Island, but the top of Shishaldin was visible above the cloud deck. An observer in Cold Bay, Alaska, called on June 29 to report increased steaming at Shishaldin during the previous couple of days. During the first full week of July, thermal anomalies increased in strength, with a return of saturated pixels (high ground temperatures). Based on this trend, as well as the persistence of the thermal anomaly, AVO elevated the Color Code/Alert Level to\r\nYELLOW/ADVISORY on July 10, 2009. Neither seismicity nor deformation had changed appreciably, and satellite data showed no significant sulfur dioxide gas emissions.\r\n\"Airborne emissions were detected in the daily analysis of satellite imagery on July 13, which was a day of rare, cloud free conditions, and a pilot also reported a steam plume rising 2,000 ft (600 m) above Shishaldin and moving to the northwest. Then, on July 15, the Ozone Monitoring Instrument (OMI) satellite imagery appeared to show a small plume-like cloud rich in SO2 originating at Shishaldin; a PUFF simulation using current winds supported the emission source as being Shishaldin.\r\n\"During the remainder of July and the first half of August, weather permitting, views of Shishaldin showed steaming from the summit. Thermal anomalies were observed in satellite images, particularly in August. A Plate Boundary Observatory (PBO) crew working on Unimak Island replaced the AVO Web camera for Shishaldin, and it began recording images on August 10; the Web camera would go off-line again on October 11, 2009.\r\n\"Following the report of a thermal anomaly on August 16, no more anomalies were detected through the remainder of 2009 except for a weak thermal anomaly on November 2. In mid-September, seemingly anomalous air waves were detected on pressure-sensors located on Shishaldin (station SSLN_BDF), which could be indicative of minor explosions. Retrospective analysis of pressure-sensor data for the previous 2 months revealed that these air waves are common phenomenon and correlated to episodic gas bursts, as documented in 2003-04 (Petersen and McNutt, 2007).\r\n\"The persistent absence of thermal anomalies, decrease in steam emissions, and seismicity considered to be within background levels, prompted AVO to downgrade the Aviation Color Code/Volcano Alert Level for Shishaldin to GREEN/NORMAL on October 19, 2009. The volcano remained quiet for the remainder of 2009.\"","StartYear":2009,"StartMonth":1,"StartDay":5,"StartTime":null,"StartQualifier":1,"StartQualifierUnit":"Months","EndYear":2009,"EndMonth":8,"EndDay":16,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Shishaldin","ParentVolcano":"Shishaldin","VolcanoID":"ak252","ParentVolcanoID":"ak252"},{"ID":811,"Name":"Veniaminof 2009/1","Description":"From McGimsey and others (2014): \"On January 8, 2009, a pilot reported seeing a wispy, light-gray plume between 6,500 and 10,500 ft (1,980 and 3,200 m), and extending 28 km (15 mi) downwind from the volcano. A passenger in an aircraft took a photograph of the plume. The AVO/USGS web camera located at nearby Perryville also captured the plume that day. \r\n   \"AVO remote sensing experts interpreted the 'gray tone' attributed to the plume to be backscatter shadow from the plume rather than ash content. Similar steaming was recorded in web camera images most of the previous week and again during the week of March 17. The web camera became inoperative on March 17 due to relocation of the village office hosting the camera. The camera would not come back online until May 27, 2009.\r\n   \"In response to an increase in seismic activity across the entire network, AVO issued a VAN on May 7, 2009, elevating the Aviation Color Code/Volcanic Alert Level to YELLOW/ADVISORY. Because the web camera was inoperative, calls to local observers on May 9 produced reports of a 'steady stream of light steam, with occasional small puffs.' Low-level tremor was recorded the week of May 18, but the activity soon diminished, and with no further visual reports of activity, on May 26, 2009, AVO issued a VAN downgrading the volcano to GREEN/NORMAL. A few days later, on May 29, tremor returned and abruptly increased later in the day. The web camera was once again operating, but the view on this day was obscured by clouds. Nothing unusual was noted in satellite images. Tremor continued through May 30, 2009, but at a lower amplitude than previously recorded, and then diminished entirely. Thus, no change in status was forthcoming.\r\n   \"On June 23-24, 2009, a small swarm of low-frequency earthquakes was recorded at Veniaminof, the last of the calendar year as the network began deteriorating. On the morning of October 19, 2009, a U.S. Coast Guard flight crew flying over Bristol Bay reported 'steady smoke and ash' coming from the center of Veniaminof. Web camera images at the time showed a voluminous, low-level steam plume over the volcano, but no indication of ash.\r\n   \"On November 17, 2009, due to continued station outage, reducing the network to only a single station, AVO issued a VAN downgrading the volcano from Aviation Color Code/Volcano Alert Level GREEN/NORMAL to UNASSIGNED, and delisting it from the inventory of seismically monitored Alaska volcanoes. The volcano would remain at this status through the remainder of 2009.\"","StartYear":2009,"StartMonth":1,"StartDay":8,"StartTime":null,"StartQualifier":7,"StartQualifierUnit":"Days","EndYear":2009,"EndMonth":10,"EndDay":19,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Veniaminof","ParentVolcano":"Veniaminof","VolcanoID":"ak301","ParentVolcanoID":"ak301"},{"ID":801,"Name":"Aniakchak 2009/2","Description":"From McGimsey and others (2014): \"Following several episodes of anomalous seismicity in 2008 (Neal and others, 2011), deep, low-frequency seismic events continued to be recorded at Aniakchak Volcano through the first half of 2009 while the seismic network was still operating. On February 27 and 28, 12 low-frequency events were recorded that had magnitudes of ML 1.0-2.1 and hypocentral depths of about 15-28 km (9.3-17.4 mi), and another sequence of events occurred on March 4 with one locatable low frequency event about 7 km (4.4 mi) depth (Scott Stihler, U.S. Geological Survey, written commun., 2011). Another burst of low-frequency events occurred at Aniakchak on June 3, 2009.\r\n   \"By September 2009, chronic station outages and data interruption prompted AVO to include Aniakchak in the list of four volcanoes considered for downgrading to UNASSIGNED. On November 17, AVO issued a Volcanic Activity Notice and an Information Statement formally declaring that Aniakchak and three other volcanoes: Veniaminof, Fourpeaked, and Korovin were no longer seismically monitored due to seismic station outages, and thus were changed from volcano alert level NORMAL and Aviation Color Code GREEN to UNASSIGNED. Two seismic stations at Aniakchak became operational by December 8, 209, but would again go out in early 2010. The network would eventually become operational again during the summer of 2010.\"","StartYear":2009,"StartMonth":2,"StartDay":27,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2009,"EndMonth":6,"EndDay":3,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Aniakchak","ParentVolcano":"Aniakchak","VolcanoID":"ak14","ParentVolcanoID":"ak14"},{"ID":610,"Name":"Redoubt 2009/3","Description":"From Schaefer (ed), 2012: \"Redoubt Volcano, an ice-covered stratovolcano on the west side of Cook Inlet, erupted in March 2009 after several months of escalating unrest. The 2009 eruption of Redoubt Volcano shares many similarities with eruptions documented most recently at Redoubt in 1966-68 and 1989-90. In each case, the eruptive phase lasted several months, consisted of multiple ash-producing explosions, produced andesitic lava and tephra, removed significant amounts of ice from the summit crater and Drift glacier, generated lahars that inundated the Drift River valley, and culminated with the extrusion of a lava dome in the summit crater. Prior to the 2009 explosive phase of the eruption, precursory seismicity lasted approximately six months with the first weak tremor recorded on September 23, 2008. The first phreatic explosion was recorded on March 15, and the first magmatic explosion occurred seven days later, at 22:34 on March 22. The onset of magmatic explosions was preceded by a strong, shallow swarm of repetitive earthquakes that began about 04:00 on March 20, 2009, less than three days before an explosion. Nineteen major ash-producing explosions generated ash clouds that reached heights between 17,000 ft and 62,000 ft (5.2 and 18.9 km) ASL. During ash fall in Anchorage, the Ted Stevens International Airport was shut down for 20 hours, from ~17:00 on March 28 until 13:00 on March 29. On March 23 and April 4, lahars with flow depths to 10 m in the upper Drift River valley inundated parts of the Drift River Terminal (DRT). The explosive phase ended on April 4 with a dome collapse at 05:58. The April 4 ash cloud reached 50,000 ft (15.2 km) and moved swiftly to the southeast, depositing up to 2 mm of ash fall in Homer, Anchor Point, and Seldovia. At least two and possibly three lava domes grew and were destroyed by explosions prior to the final lava dome extrusion that began after the April 4 event. The final lava dome ceased growth by July 1, 2009, with an estimated volume of 72 Mm3.\"\r\n\r\nWallace and others (2012) calcuate a total Dense Rock Equivalent of about 0.02 cubic meters for tephra fall from the Redoubt 2009 eruption.","StartYear":2009,"StartMonth":3,"StartDay":15,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2009,"EndMonth":7,"EndDay":null,"EndTime":null,"EndQualifier":1,"EndQualifierUnit":"Months","Volcano":"Redoubt","ParentVolcano":"Redoubt","VolcanoID":"ak231","ParentVolcanoID":"ak231"},{"ID":791,"Name":"Sanford 2009/3","Description":"   From McGimsey and others (2014): \"On March 18 and 19, 2009, local Copper River Basin residents observed a large, unusual cloud emanating from the summit of Mount Sanford volcano (figs. 2-4). AVO was alerted on March 19 because the cloud had persisted for more than 24 hours and some residents were concerned that the cloud indicated volcanic activity. The cloud was reported to extend for more than 50 km (30 mi). The plume was visible March 19 on a webcam located at the High Frequency Active Auroral Research Program (HAARP) facility, 29 km (18 mi) north of Glennallen, Alaska, but the view was 'all clear' at Sanford from this camera on March 20. From the vantage point of most residents of the Copper River Basin, this cloud appeared to be a feature unique to Sanford; however, AVO remote sensing specialists examining satellite images of the region reported that this was one of several orographic clouds streaming off the higher mountain peaks in the area. AVO issued an Information Statement on March 20 to report and explain the observations.\"","StartYear":2009,"StartMonth":3,"StartDay":18,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2009,"EndMonth":3,"EndDay":19,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Sanford","ParentVolcano":"Sanford","VolcanoID":"ak242","ParentVolcanoID":"ak242"},{"ID":611,"Name":"Cleveland 2009/6","Description":"From McGimsey and others (2014): \"For the next three months [following the short-lived eruption in January, 2009], no significant activity was reported or observed at Cleveland, and on May 1, 2009, AVO downgraded the Aviation Color Code and Volcano Alert Level to UNASSIGNED. Then, on the morning of June 25, 2009, satellite imagery caught a small eruption occurring that sent an ash plume up to about 15,000 ft (about 4,600 m) and ballistics onto the upper flank snowfields. As with several previous eruptions, air waves generated by the event were registered on seismometers at nearby volcanoes (M. Haney, AVO/USGS, written commun., 2009, AVO internal logs). AVO promptly elevated the Color Code/Alert Level from UNASSIGNED to ORANGE. When observed, the plume was already detached and moving south over the North Pacific. Based on no further reports or evidence of activity over the next several days, AVO lowered the Color Code/Alert Level to YELLOW/ADVISORY on June 27. The volcano remained quiet for the next couple of weeks, and on July 15, the Color Code/Alert Level was downgraded to UNASSIGNED. No activity was observed or reported during the subsequent 2.5 months.\"","StartYear":2009,"StartMonth":6,"StartDay":25,"StartTime":"11:15:00","StartQualifier":2,"StartQualifierUnit":"Hours","EndYear":2009,"EndMonth":6,"EndDay":25,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":612,"Name":"Cleveland 2009/10","Description":"From McGimsey and others (2014): \"On October 2, 2009, another small eruption occurred at Cleveland. Satellite images from 08:11 and 08:25 UTC (00:11 and 00:25 am AKDT) on October 3, 2009, showed a detached ash cloud moving to the northeast away from the volcano. The HYSPLIT particle trajectory model calculated a 6-km-high (20,000 ft) plume originating at about 07:15-07:30 UTC on October 3 (11:15-11:30 pm AKDT). A strong ash signal was indicated from analysis of the satellite data. The cloud was 40 km long (25 mi), 12 km wide (7.5 mi), and 122 km (76 mi) from the volcano at 08:25 UTC (October 3). By 10:00 UTC (02:00 am AKDT on October 3), the cloud was 231 km (144 mi) from the volcano. In response to this activity, AVO upgraded the Aviation Color Code/Volcano Alert Level to ORANGE/WARNING at 02:29 am AKDT (10:29 UTC) on the morning of October 3, 2009.\r\n\"Activity decreased as abruptly as it had started, and on the afternoon of October 5, 2009, the Color Code/Alert Level was downgraded to YELLOW/WATCH. Clear satellite views, particularly on October 15 and 19, showed no further signs of activity, and on October 19, 2009, status of the volcano was downgraded to UNASSIGNED. Cleveland remained quiet almost until the end of 2009. A small, low-level ash plume was emitted on December 12, 2009, but there were no changes to the status for the remainder of 2009.\"","StartYear":2009,"StartMonth":10,"StartDay":2,"StartTime":"23:30:00","StartQualifier":null,"StartQualifierUnit":null,"EndYear":2009,"EndMonth":12,"EndDay":12,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":901,"Name":"Makushin 2010/2","Description":"From Neal and others (2014): \"Low level seismicity was recorded at Makushin Volcano throughout 2010. At about 7:00 p.m. Alaska Standard Time on February 17, a veteran pilot noted an unusual dark plume over the volcano during exceptionally clear conditions. Later, Guardian Flight paramedic Wayne Boots sent AVO images of strong fumarolic output at the Makushin summit from February 19. AVO reviewed seismic data and saw no change of any significance related to a possible plume. On February 24, a strong vapor plume was visible with satellite imagery but again, no change in seismicity was noted. On March 3, AVO satellite analysts reported slightly elevated temperatures in the vicinity of the summit craters; not an unusual observation for the fumarolically active summit of Makushin.\r\nSeismicity increased slightly with a small swarm on April 7 and again in May. AVO did not elevate the Aviation Color Code or Alert Level for Makushin for either of these slight departures from background.\"","StartYear":2010,"StartMonth":2,"StartDay":17,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2010,"EndMonth":5,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Makushin","ParentVolcano":"Makushin","VolcanoID":"ak188","ParentVolcanoID":"ak188"},{"ID":841,"Name":"Sanford 2010/3","Description":"From Neal and others (2014): \"On March 23, a consulting geologist working in the area reported seeing a 'good size plume' from Sanford on 2 night. A number of Copper River Valley residents shared photographs of Sanford from March 15 when a dramatic looking plume emated from the southern flank and summit of the volcano.\r\n\"A similar cloud was reported on October 20 by Pete Dalton, District Ranger for the National Park Service, stationed at the Gulkana Airport. According to Pete Dalton, the plume rose about 2000 to 3000 ft above the summit. AVO received multiple calls regarding the October 20 plume, which appeared to originate from several points on the near-vertical, rocky southern face of the volcano. A towering vapor cloud emanating from the steep rocky face of this volcano has been reported before (McGimsey and others, 1999) and may be related to rock and ice-fall activity, solar warming of the rock and ice face, or a combination of processes. No features related to volcanic heat sources have been documented on Mount Sanford; however, no comprehensive thermal survey has been done.\"","StartYear":2010,"StartMonth":3,"StartDay":15,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2010,"EndMonth":10,"EndDay":20,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Sanford","ParentVolcano":"Sanford","VolcanoID":"ak242","ParentVolcanoID":"ak242"},{"ID":621,"Name":"Cleveland 2010/5","Description":"From Neal and others (2014): \"A sudden and sustained increase in surface temperature in May prompted AVO to upgrade the Aviation Color Code and Volcano Alert Level from UNASSIGNED to YELLOW/ADVISORY on May 25 [2010]. After consistent thermal anomalies during the last week of May, AVO remote sensors detected a small ash plume on satellite imagery on May 30. The plume was traveling at an estimated altitude of 16,000 ft ASL and drifting south. \r\nASTER acquired a mostly clear view of Cleveland on June 1. Recent dark flowage deposits are visible on the eastern flank and tephra-fall deposits blanket a swath to the southwestern coastline. The summit crater was hidden by a white vapor cloud.\r\nFollowing the impulsive ash event on May 30, AVO ceased to detect consistently elevated surface temperatures and, without additional observations of activity, AVO returned the volcano to UNASSIGNED on June 11.","StartYear":2010,"StartMonth":5,"StartDay":30,"StartTime":"19:56:00","StartQualifier":null,"StartQualifierUnit":null,"EndYear":2010,"EndMonth":5,"EndDay":30,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":622,"Name":"Cleveland 2010/9","Description":"From Neal and others (2014): \"On 18 July, 2010, a magnitude 6.6 main-shock occurred 9 km (5.6 mi) northeast of the summit of Mount Cleveland. AVO field personnel on Umnak Island reported that buildings shook and fuel barrels rolled back and forth several inches (M. Kaufman, UAFGI/AVO, written commun., 2010). The earthquake also was felt in Unalaska/Dutch Harbor, although residents described the shaking as 'light' or 'weak'. \r\n\"This event triggered a subsequent earthquake cluster of more than 1,800 aftershocks greater than magnitude 2.5 and about 110 magnitude 4.0 or greater events. According to analysis by AEIC, a M 4.0 foreshock had occurred on July 17 at 14:44 UTC. Earthquakes during this time period were restricted to an approximately 25-km-wide (15-mi) area extending from eastern Chuginadak Island to the edge of the Aleutian platform about 60 km (37 mi) southeast. The largest aftershock of magnitude 6.0 occurred on July 18.\r\n\"AEIC analysis of fault plane solutions for the large events of this series determined that the larger earthquakes were located on north-northwest-trending normal faults. This was the largest event to occur in the region since the magnitude 6.5 earthquake on October 13, 2009. Similar sized earthquakes occurred in the same area on May 10, 2006, and December 26, 2007. AEIC located nearly 3,200 aftershocks through end of July, including about 60 aftershocks with magnitudes 4.0 or greater.\r\n\"The earthquake had no clear impact on Cleveland volcano; however, elevated surface temperatures reappeared at the summit throughout July and August. Based on this, AVO upgraded the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY on August 26. On August 26, 29, and 31, pilots from Alaska Airlines flying the Anchorage to Adak route reported no volcanic ash from Mount Cleveland. Thermal anomalies continued into September but did not intensify; on September 10, the Aviation Color Code and Alert Level were downgraded to UNASSIGNED.\r\n\"On September 12, the Anchorage VAAC reported a possible weak ash signal in satellite data. If this was an eruption cloud, the plume rose only a few thousand feet above the volcano's summit and disspated quickly. A one-time VAA was released but no SIGMET was issued. AVO upgraded the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY. Observations from a pilot in the area of Mount Cleveland reported that no ash was visible, at least below 2,900 ft. Clear satellite views continued to show elevated surface temperatures in the summit crater but no ash plumes.\r\n\"Clouds frequently prevented remote viewing of the volcano but during periods of clear conditions, thermal anomalies were noted intermittently through the end of the year. AVO maintained Cleveland at Aviation Color Code and Volcano Alert Level YELLOW/ADVISORY. There were no reports of ash or other activity except for an anomalous infrasound signal that was received on September 15 at 00:24 and 00:30 UTC (Steve McNutt, UAFGI/AVO, written commun., 2010) and may have represented a small explosion from the volcano.\"\r\nWeak thermal anomalies were visible on January 1, 11, and 16 [2011], and the weather remained cloudy for the remainder of the month.\r\nIn February, a weak thermal anomaly was observed on the first. On the 9th, a pilot overflew Cleveland and reported minor, repetetive steam emissions rising hundreds of feet above the summit. The snow on the flanks was pristine, with no indication of recent ash emissions. Steam emissions are common at Cleveland and do not indicate an increased level of unrest.\r\nIn March, a weak thermal anomaly was observed on March 2, 3, and 11. A cloud-free view of the volcano on March 23 showed no unusual activity. On March 31, 2011, AVO lowered the volcano alert to UNASSIGNED and the aviation color code to UNASSIGNED, on the basis of a lack of confirmed eruptive activity over the past several months.","StartYear":2010,"StartMonth":9,"StartDay":12,"StartTime":null,"StartQualifier":1,"StartQualifierUnit":"Days","EndYear":2011,"EndMonth":3,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":692,"Name":"Cleveland 2011/7","Description":"From McGimsey and others (2014): \"On July 20, AVO upgraded the Aviation Color Code/Volcano Alert Level from UNASSIGNED to YELLOW/ADVISORY after thermal anomalies were observed in satellite imagery during routine satellite monitoring on July 16-17. On August 2, the Aviation Color Code/Volcano Alert Level was upgraded to ORANGE/WATCH based on persistent thermal anomalies detected at the volcano's summit as well as satellite evidence of new lava in the summit crater on July 31.\r\n\"In 2011, Cleveland's summit crater was about 200-225 m (660-740 ft) wide at the rim; its depth varies through time with the impacts of eruptive activity, but can be as much as 80-100 m (260-330 ft). Extrusion of lava in the summit crater presumably began around the time of the onset of persistent thermal anomalies, during July 16-17; a new dome in late July 2011 was approximately 40 m (130 ft) across. Satellite images of the summit on August 3 showed the dome to be approximately 50 m (160 ft) across and no more than 20 m (65 ft) above the summit crater floor. The dome may have grown to 60 m (200 ft) across by August 6 implying an approximate lava volume of 115,000 cubic meters (150,420 cubic yards) or 7 percent of the crater's total volume of approximately 1,6 million cubic meters (2,1 million cubic yards). Satellite imagery showed no significant new tephra deposits indicating that activity from mid-July into early August was primarily extrusive. This was consistent with an August 9 WorldView-1 satellite image of Cleveland's summit showing steaming, light-colored alteration deep inside the summit crater around the new lava dome, and with oblique aerial photographs taken on August 8 by NOAA scientists. \r\n\"On August 10, AVO received a mariners report from the National Weather Service (NWS) Ocean Prediction Center of possible ash floating on the sea surface approximately 25 km (13,5 nmi) north-northwest of Cleveland. The same source reported the absence of any floating ash earlier in the day at about 30 km (16 nmi) north of the volcano. No ash clouds were detected in satellite data during the times of the these reports. Analysis of satellite data indicated that during August 6-13, the lava dome grew only slightly larger than detected in the previous image acquired August 6. Although it is possible that these accounts of drifting ash are valid, AVO was unable to confirm them.\r\n\"On August 30, AVO downgraded Cleveland's Aviation Color Code/Volcano Alert Level from ORANGE/WATCH to YELLOW/ADVISORY, based on the absence of distinct thermal signals at the summit. Satellite observations on September 6 indicated that the lava dome had grown to about 120 m (390 ft) in diameter and consistently elevated surface temperatures were again observed. As a result of these observations, AVO upgraded Cleveland to Aviation Color Code/Volcano Alert Level ORANGE/WATCH. By this time, the lava dome essentially filled the summit crater. \r\n\"TerraSAR-X satellite radar images from the German Remote Sensing Data Center (DFD) and the German Aerospace Center (DLR), acquired over Cleveland volcano from August to November 2011, provided an image time series showing the partial growth of the 2011 lava dome in the summit crater.\r\n\"The lava dome continued to grow through late September, expanding in diameter from approximately 120 m (390 ft) on September 6 to approximately 168 m (550 ft) by September 20, and reaching a height approximately 15-20 m (50-60 ft) below the crater rim by September 26. Additional growth of the lava dome past October 20 was minor.\r\n\"Extrusion of lava either slowed or ceased between October 1 and October 5. Satellite data from October 9 indicated that the central portion of the lava dome became slightly depressed, indicating minor deflation of th edome. Subsidence of the dome continued into late October.\r\n\"AVO downgraded Cleveland's Aviation Color Code/Volcano Alert Level from ORANGE/WATCH to YELLOW/ADVISORY on November 3 based on the absence of consistent thermal anomalies in satellite images and apparent cessation of lava effusion after October 9.\r\n\"On November 10, satellite images showed that a small secondary dome had emerged atop the center of the semi-deflated lava dome. The diameter of this new dome was approximately 15-20 m (50-65 ft) and it likely began to grown on or before November 2. The original dome remained unchanged in size.\r\n\"Lava within the summit crater remained mostly unchanged from November 10 to November 24. A satellite image from November 25 showed that the small secondary dome had subsided into a broad blocky, hummocky depression approximately 70 m (230 ft) in diameter and the overall dome had subsided approximately 30 - 35 m (100-115 ft) from its maximum elevation in early October. The dome continued to subside into early December, and by December 7, nearly the entire extrusive feature had collapsed into the conduit and its surface was approaching the pre-August crater-floor elevation.\r\n\"On December 29 at approximately 04:12:07 AKST (13:12:07 UTC), an explosion from Cleveland produced a small ash cloud that rose to approximately 3.5 km(11,500 ft) ASL. The ash cloud drifted to the east and over the southwestern tip of Umnak Island. The eruption triggered two operational ash alarms used by AVO. The first alarm was triggered at approximately 05:33 AKST (14:33 UTC) indicating likely ash signatures in NOAA's AVHRR satellite image n19.11363.1402. A NOAA-NESDIS ash cloud alarm was triggered at approximately 05:34 AKST (14:34 UTC) from the same AVHRR satellite image. Calculations based on the satellite data and local meterologic conditions indicated a maximum ash cloud height of 3.5 km (11,500 ft) ASL, with a mean effective ash particle radius of 5.06 microns (1,99 x 10^-4 in.), a total mass of 0.84 kt (925 tons), and a total area of 173 square km (66.8 square miles) (M. Pavolonis, written commun., December 29, 2011). \r\n\"In response to the ash cloud, AVO upgraded the Aviation Color Code/Volcano Alert Level from YELLOW/ADVISORY to ORANGE/WATCH at 07:55 ASKT (16:55 UTC) on December 29, 2011.\r\n\"Infrasound signals from the December 29 explosion were first detected on seismic stations and infrasound arrays deployed at Okmok volcano, located approximately 139 km (90 mi) northeast of Cleveland on Umnak Island. Infrasonic waves are sound waves that span a frequency range from below 20 Hz (the lower limit of human hearing) to 0.001 Hz. Infrasound signals are recorded at seismic stations by the infrasound airwaves coupling with the ground at seismic station(s) and mechanically vibrating the ground in which the seismometer sits. The recorded seismic signal is known as a ground-coupled airwave produced by a volcanic explosion or eruption. Based on the speed of sound in Earth's atmosphere and the distance between seismic station OKWE and the summit of Cleveland the origin time of the explosion was calculated at approximately 04:12:04 AKDT (13:12:07 UTC) (Matt Haney, David Fee, and Silvio de Angelis, UAFGI, written commun., December 29, 2011).\r\n\"AVO downgraded the Aviation Color Code/Volcano Alert Level for Cleveland volcano from ORANGE/WATCH to YELLOW/ADVISORY at 13:57 AKST (22:57 UTC) on December 29 following no additional reports of eruptive activity occurring at the volcano. Cleveland remained at Aviation Color Code/Volcano Alert Level YELLOW/ADVISORY throughout the remainder of 2011.\r\n\"A review of the infrasound data prior to the December 29 explosion revealed several small explosive eruptions from Cleveland volcano on December 25. The first occurred at approximately 03:13 AKST (12:13 UTC) and had an infrasound amplitude of approximately one-half the December 29 event. The second eruption occurred on December 25 at approximately 06:32 AKST (15:32 UTC).\r\n\"A small ash cloud was retrospectively detected in satellite imagery for the December 25 event. The eruption cloud was very minor, did not have a large ash signal at the image's collection time of 06:32 AKST (15:32 UTC), and was only weakly visible in a thermal infrared image. The cloud had dissipated by the time the next image was acquired at 06:46 AKST (15:46 UTC).\r\n\"Satellite data from December 26 displayed evidence of ejected blocks that had rolled down the upper northern and western flanks of the volcano, some as far as about 1.5 km (5,000 ft) from the crater's rim. There was no indication of fresh ash deposits on the volcano's upper northern and western flanks.\"\r\nFrom Herrick and others (2014): \"On January 30, a new lobe of lava about 40 m (130 ft) across was detected at the bottom of the summit crater. On January 31, the Aviation Color Code and Volcano Alert Level was upgraded to ORANGE/WATCH due to the presence of this small lava flow and the increased potential for explosive dome destruction.\r\n\"On February 3, satellite data showed no significant change within the summit crater. By February 7, the dome had grown to about 50 m (160 ft) across and 1 week later, 60 m (200 ft). On February 22, additional new lava had broken the surface of the dome producing a 20-m-diameter (66-ft) lobe atop the existing lava pad. Evidence of continued effusion was reported through the end of February and slightly elevated temperatures were reported during clear conditions.\r\n\"Three explosions occurred from the Cleveland summit crater in the first 2 weeks of March; the March 8 explosion produced a small ash cloud that dissipated quickly. Details of how much of the new lava dome was destroyed in each explosion are unknown, but by March 11, it was entirely removed. Cloudy conditions prevailed and ash emissions that may have been produced after March 8 went unnoticed. On March 23, the Aviation Color Code and Volcano Alert Level was downgraded to YELLOW/ADVISORY based on the lack of evidence of renewed lava effusion.\r\n\"On March 26, a new lava flow about 70 m (230 ft) across was detected within the crater. On March 28, the Aviation Color Code and Volcano Alert Level was upgraded to ORANGE/WATCH. By April 4, the dome was gone, likely removed in an explosion at about 09:12 UTC on April 4. Subsequent satellite images showed that large blocks, 15-20 m (50-65 ft) across, littered the crater floor. Four additional explosions occurred between April 7 and April 19 during a period of frequently elevated temperatures detected in satellite images. No unequivocal ash clouds were detected following each event; however, weather and satellite overpass timing could have played a role. The AVO Web camera was not functioning during this time.\r\n\"Elevated surface temperatures persisted through April and into May. By April 25, a new dome had appeared in the crater, only to be destroyed sometime before April 29. An ambiguous seismic event had been recorded by the Makushin network at 16:14 UTC on April 29. It may have been related to the dome’s demise, but this remains inconclusive (M. Haney, USGS/AVO, written commun., November 2013). On May 3, the third detected lava flow of 2012 was observed in the crater forming a dome about 25 m (82 ft) in diameter.\r\n\"Explosions occurred on May 4 and 5, but no ash cloud or strong thermal signal was noted for either event. Satellite observations on May 6 showed that the May 3 lava dome was gone, presumably destroyed during the May 4-5 explosions. After 3 weeks with no further explosions and only rare instances of elevated surface temperature, the Aviation Color Code and Volcano Alert Level was downgraded to YELLOW/ADVISORY on May 30. An AVO staff member flying near Cleveland noted white steam rising from the crater.\r\n\"Cleveland remained at YELLOW/ADVISORY despite the detection of another explosion by infrasound on June 4. Only minor tephra and possibly flowage deposits were noted on a June 9 satellite image. On June 19, an explosion produced an ash cloud seen by a pilot, and the cloud also was captured on the AVO Web camera and detected by infrasound. The pilot estimated the cloud height to be 35,000 ft (11 km) ASL. Following detection of the explosion and confirmation of a high ash cloud, AVO upgraded the Aviation Color Code and Volcano Alert Level to ORANGE/WATCH.\r\n\"Several more explosions occurred in late June, July, August, and November; all were detected either on infrasound networks or distant seismic stations. Three of these produced small ash clouds detected by satellite images and one by the AVO Web camera. Satellite observations of the volcano documented minor changes in the summit crater but no additional, intact lava flows were noted through the end of 2012.\"\r\nFrom Dixon and others (2015): \"Early in 2013, a faint white steam cloud emanating from the summit crater was occasionally seen in satellite images. On January 30, 2013, after more than a week of consistently elevated temperatures in AVHRR images, satellite observations indicated a new lava flow inside the summit crater (table 8 in original text). Extrusion began sometime after January 7, when clear satellite images showed no lava in the crater, and before the January 30 satellite image showing a new lava flow. The round dome-like feature was about 100 m across. Significantly elevated temperatures continued in satellite images, visible even in fairly cloudy conditions. By February 9, a second lava extrusion 25 m (82 ft) across was perched across the late January dome. After learning of the existence of new lava in the summit crater, AVO upgraded the Aviation Color Code and Volcano Alert Level on February 6 to ORANGE/WATCH. AVO downgraded to YELLOW/ADVISORY on March 8 after no further escalation of activity.\"","StartYear":2011,"StartMonth":7,"StartDay":16,"StartTime":null,"StartQualifier":7,"StartQualifierUnit":"Days","EndYear":2013,"EndMonth":1,"EndDay":null,"EndTime":null,"EndQualifier":1,"EndQualifierUnit":"Months","Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":693,"Name":"Kanaga 2012/2","Description":"From Herrick and others (2014): \"An increase in seismic activity at Kanaga was first noted on February 18 during a routine seismic check by AVO seismologist S. Stihler, who reported a tremor-like event (interpreted as a possible explosion) followed by smaller events over the next hour. A possible correlative airwave occurred on the Adak seismic station 40 km (25 mi) northeast of Kanaga about 2 minutes after the tremor event (M. Haney, USGS/AVO, written commun., 2012). Ten minutes after the tremor event, a faint ash signal in satellite images may have been a small ash cloud from Kanaga, drifting to the east at an altitude of about 6 km (19,700 ft) ASL. Based on these observations, AVO upgraded the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY. Additional analysis of the seismic signal, 'reduced displacements,' showed relatively small values, consistent with hydrothermal or possibly phreatic activity (S. McNutt, UAFGI, written commun., 2012).\r\n\"Adak resident M. Tillion contacted AVO by telephone on February 19 to share photographs and observations of Kanaga on the day after the possible explosion at about 12:26 Adak time or 10:26 UTC. From the White Alice site, west of the community of Adak, a resident noted an acrid odor that caused throat irritation. Kanaga volcano, 37 km (23 mi) northwest of Adak, was steaming strongly from the summit; M. Tillion thought that the plume may have contained some ash but further analysis suggests these were just shadowed clouds. There was, however, evidence of tephra or flowage deposits on the eastern flank extending down from the summit area.\r\n\"Cloudy conditions prevented any direct observations throughout much of February. Slightly elevated surface temperatures at the summit were noted in satellite images on February 21. On February 23, four bursts of tremor-like events were recorded on the Kanaga network. Satellite images from February 26 showed that the summit crater was clear with no evidence of ongoing eruptive activity. Seismicity remained low and on March 2, AVO downgraded the Aviation Color Code and Volcano Alert Level to GREEN/NORMAL, where it remained for the rest of the year.\r\n\"Retrospectively, the combination of satellite images, aerial photographs, and field inspection demonstrated that a brief explosive event from Kanaga's summit had indeed occurred, modifying the summit crater and producing a very small tephra fall deposit. A March 5 satellite radar image clearly showed a new open fissure along the southern rim of the summit crater. The feature was about 600 m (1,970 ft) in length and continued a short distance down the upper western flank of the volcano. In places, the fissure was 15 m (50 ft) wide and white clouds of vapor issued from several points along the fissure. An additional fumarolic cloud issued from the 15-m-diameter (50-ft), circular hole in the bottom of the crater. On March 9, nearly 3 weeks after the explosion signal, no ejecta or ash fall deposits were noted in satellite images, however, additional snowfall and reworking on the steep flanks likely would have obscured any primary deposits. Given the transient nature of the event, the limited tephra fall, and residual steaming fissure, AVO concluded that this event was a sudden phreatic explosion originating in the shallow, hydrothermally active summit region of Kanaga. The orientation and location of the feature has no clear relationship to the 1993-1995 eruptive vent complex that involved effusion of lava and ash from both the summit crater and a fissure system on the upper eastern flank of the volcano (Neal and others, 1995; Waythomas and others, 2002).\r\n\"Notable plumes of white vapor from Kanaga's summit were seen throughout the spring by ship and airborne observers as well as Adak residents. Ship-based observers on April 1 suggested that three distinct locations along the fissure were producing the most intense clouds. At least one satellite image on April 1 showed a possible plume from the summit. Bursts of seismicity were noted in mid- and late April. The seismic record was hampered by periods of noise and scattered data outages in late spring and early summer.\r\n\"An AVO crew working via helicopter on the Kanaga seismic network in mid-June was able to describe the fissure and apparently new ash on the northern and eastern flanks; they were unable to land and inspect the volcano's summit area, however, due to high winds. Steam was steadily rising from the summit fissure. On June 20, a faint sulfur odor was detected at the KINC seismic station located 2 km (1 mi) to the east of the volcano summit; our limited experience on the volcano makes it difficult to know how atypical this observation is from normal conditions. The team noted traces of what appeared to them to be recent ash on the northern flank down to an elevation of about 250 m (820 ft) ASL.\r\n\"Aerial photographs by Roger Clifford in both summer and fall provided excellent views of the summit fissure. Figure 29 shows a summer image of the nearly snow-free Kanaga cone; the fissure can be seen wrapping around and just outboard of the summit crater rim. The maximum opening across the fissure is about 15 m (50 ft) and white vapor issues from several point sources within the fissure. In November, Roger Clifford captured the western extent of the fissure where it crosses the summit and extends about 100 m (330 ft) down the western flank.\r\n\"Brief episodes of elevated seismicity occurred during the rest of the year at Kanaga. On June 27, unusual, emergent seismic events were detected on records from the northern seismic stations of the Kanaga network. Periods of tremor also were noted. The significance of this seismicity with respect to the summit fissure or ongoing activity at Kanaga is unknown.\r\n\"Satellite and seismic data from before February 18 was further analyzed to look for any changes prior to the explosion and opening of the summit fissure. A satellite image from January14, 2012, showed no structure in the area later cut by the fissure, although the southern rim was bare and lightly steaming. In October 2011, an unusual series of low frequency earthquakes had been noted, but any relationship of this to the 2012 activity remains unclear.\r\n\"In response to this event, AVO established automated PUFF runs to simulate ash cloud trajectories in the event of a magmatic eruption, increased the frequency of daily satellite checks, and attempted limited field verification of events in conjunction with seismic network maintenance.\"","StartYear":2012,"StartMonth":2,"StartDay":18,"StartTime":"06:23:00","StartQualifier":null,"StartQualifierUnit":null,"EndYear":2012,"EndMonth":2,"EndDay":18,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Kanaga","ParentVolcano":"Kanaga","VolcanoID":"ak144","ParentVolcanoID":"ak144"},{"ID":951,"Name":"Little Sitkin 2012/8","Description":"From Herrick and others (2014): \"Seismic activity at Little Sitkin began to increase on August 22. Although volcano-tectonic earthquakes accounted for most of the seismicity, some unusual signals also were observed, most notably monochromatic earthquakes. A series of 5 monochromatic earthquakes that had unusually low resonant frequencies (0.6 Hz) that occurred during August 24-28. These earthquakes occurred at depths depths between 10 and 20 km (6-12 mi) and were recorded on seismic stations as far away as 80 km (50 mi) on Amchitka and Semisopochnoi Islands. These signals at Little Sitkin appear similar to that seen at Izu-Oshima Volcano in Japan (Ukawa and Ohtake, 1987). Two brief episodes of tremor also were recorded during this time.\r\n\"On August 30, earthquake activity escalated dramatically, prompting AVO to upgrade the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY. AVO instituted a heightened seismic watch schedule to examine seismic data every 2 hours. An RSAM alarm was established for Little Sitkin to alert seismologists in the event of a sudden escalation in seismicity. Frequent earthquakes continued through August 31, then decreased during the first few days of September. Of the 110 earthquakes located during the first week of September, epicenters averaged 3.5 km (2.2 mi) from the summit. After a short flurry of earthquakes on September 13, seismicity decreased, but remained well above background. On September 24, AVO reduced the frequency of seismic data checks to once every 6 hours.\r\n\"Over the next 3 months, seismicity consisted of low-frequency tremor bursts with occasional brief swarms of VT events. Three notable flurries of seismicity occurred on October 13, 15, and 29. Another pulse of VT activity began on November 15 and continued through November 26. Six?hour seismic checks for Little Sitkin were discontinued on October 8.\r\n\"On January 9, 2013, after more than a month of relative quiet and continued decrease in overall seismicity, AVO downgraded the Aviation Color Code and Volcano Alert Level to GREEN/NORMAL. (Note that prior to the onset of seismicity and upgrade to YELLOW/ADVISORY in August, the volcano had been designated UNASSIGNED. Technically, it should have returned to UNASSIGNED, but this did not happen until March 29, 2013).\r\n\"Satellite images of the largest hot spring area west of the modern Little Sitkin cone showed that no significant change had occurred in the area since the last observations in late-October and early-September 2012. AVO received no reports from mariners or air crews of any changes at the surface; however, this part of the Aleutian Arc receives few visitors throughout the year and minor changes in activity could well go unnoticed.\r\n\"Subsequent analysis of InSAR results from images that span the time period of increased seismicity indicates 1-2 cm (0.4-0.8 in.) of inflation beneath the modern Little Sitkin cone. This result, along with the evolution of the seismic sequence in 2012, strongly suggests a magmatic intrusion as the source of observed seismicity and geodetic change (Haney and others, 2014).\"","StartYear":2012,"StartMonth":8,"StartDay":22,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2012,"EndMonth":11,"EndDay":26,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Little Sitkin","ParentVolcano":"Little Sitkin","VolcanoID":"ak182","ParentVolcanoID":"ak182"},{"ID":4311,"Name":"Geyser Bight 2013","Description":"From Dixon and others, 2017: \"The Geyser Bight Valley is a geothermal area (Nye and others, 1992; Motyka and others, 1993) southeast of Mount Recheshnoi (fig. 21 [original text]). In 2007, the seismograph network on neighboring Okmok Caldera recorded a short earthquake swarm in October. Following a 5-year period of quiescence, seismic activity increased in the Geyser Bight area in 2013 and continued through July 2015. The vast majority of the earthquakes located in 2015 were at shallow depths, less than 7 km (4 mi) with earthquake magnitudes between ML= 0.5 and ML=1.5. Seven earthquakes were larger than ML=2.0; the largest earthquake was a ML=3.0 event on June 30. Because this sequence of earthquakes occurred well away from a historically active volcano, no change in the alert status was made at any neighboring volcanoes.\"","StartYear":2013,"StartMonth":null,"StartDay":null,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2015,"EndMonth":7,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Recheshnoi","ParentVolcano":"Recheshnoi","VolcanoID":"ak229","ParentVolcanoID":"ak229"},{"ID":1091,"Name":"Okmok 2013/3","Description":"From Dixon and others (2015): \"No eruptive activity was reported at Okmok Volcano, but seismic and geodetic observations of note were made in 2013. Sporadic tremor episodes and three swarms of earthquakes caught the attention of duty personnel in 2013. Geodetic instruments within the Okmok caldera detected a mid-year pulse of inflation. The Aviation Color Code and Volcano Alert Level remained at GREEN/NORMAL throughout the year.\r\n   \"On March 7, a 36-hour long swarm of over 1,000 low-frequency earthquakes was recorded on seismograph station OKTU, a station on Mount Tulik just outside the caldera (fig. 37 in original text). These earthquakes were too small to be recorded on adjacent stations and could not be located. The earthquakes formed two groups of earthquakes with similar waveforms (or earthquake families) that began at the same time, with the first earthquake family continuing for the duration of the swarm and the second family lasting for about the first 6 hours (fig. 38 in original text). Family 2 (short-duration family) contained larger events than family 1. After the family 2 (short-duration family) events ceased, the events in family 1 became larger and more infrequent than events earlier in the same earthquake family. Towards the end of the swarm, the event interval became more erratic, and the swarm ended abruptly.\r\n   \"Beginning in May 2013, the geodetic network at Okmok detected a pulse of rapid inflation, one of the steepest rises at Okmok since the 2008 eruption (fig. 39 in original text). The spatial pattern of the deformation is similar to past inflation events at Okmok, and points to an inflation source beneath the center of the caldera. In a study of ambient noise correlations between the Okmok stations OKNC and OKCE, evidence was found of 0.2-percent decrease in seismic velocity during late August and September within the caldera, indicating a change in composition of the crust sampled by the ray paths (Matt Haney, USGS/AVO, written commun., 2013). The geodetic and seismic evidence suggests an infusion of fluid or gas and, although it is certain that this was a change, it is not clear whether this change was magmatic or hydrologic.\r\n   \"A swarm of earthquakes began at 01:55 UTC on September 28 (17:55 AKDT on September 27) southwest of Okmok and northeast of Mount Recheshnoi in an active geothermal area. A second swarm occurred at Geyser Bight on October 9, forming a continuous zone of seismicity that extends from Recheshnoi towards Okmok (fig. 40 in original text). Neither swarm has led to eruptive activity and has continued to occur into 2014.\"\r\nFrom Cameron and others, 2017: \"Okmok volcano continued to inflate during 2014-a \r\ngeneral trend that started no more than 3 weeks after the volcano’s 2008 eruption (Freymueller and Kaufman, 2010). More specifically, analyses of GPS and InSAR data from 2008 to present (2016) show evidence for two major pulses of post-eruptive inflation (Qu and others, 2015). Inflation of the volcano began at a rapid rate immediately after eruption and slowed with time, largely ceasing by mid-2013. A new pulse of rapid inflation began at that time, its rate slowly decreasing over time. Inflation continued through 2014, although at a much slower rate.\"","StartYear":2013,"StartMonth":3,"StartDay":7,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2014,"EndMonth":12,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Okmok","ParentVolcano":"Okmok","VolcanoID":"ak206","ParentVolcanoID":"ak206"},{"ID":1101,"Name":"Korovin 2013/3","Description":"From Dixon and others (2015): \"Starting on March 29, Korovin Volcano experienced a 2-week-long swarm of small earthquakes located 2-4 km (1.2-2.4 mi) northwest of the summit of Korovin. Earthquake activity peaked on April 10, with a rate of 10 earthquakes per hour, and the swarm ended by April 12 (fig. 45 in original text). Throughout 2013, AVO noted isolated tremor at Korovin. In comparison, this tremor released about one-third of the energy level of tremor associated with a 2006 period of unrest at Korovin. The Aviation Color Code and Volcano Alert Level remained UNASSIGNED/UNASSIGNED throughout the year.\"","StartYear":2013,"StartMonth":3,"StartDay":29,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2013,"EndMonth":4,"EndDay":12,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Korovin","ParentVolcano":"Atka volcanic complex","VolcanoID":"ak171","ParentVolcanoID":"ak17"},{"ID":1031,"Name":"Fourpeaked 2013/4","Description":"From Dixon and others(2015): \"A minor increase in seismicity at Fourpeaked Volcano in April and May prompted additional analysis of monitoring data by AVO. AVO also received a report in May of steaming near Mount Douglas and Fourpeaked. During 2013, the Aviation Color Code and Volcano Alert Level for Fourpeaked remained at GREEN/NORMAL.\r\n   \"A ML=4.5 earthquake occurred just west of Fourpeaked at 06:34 UTC (22:34 AKDT) on May 12. The Alaska Earthquake Information Center (AEIC) located this earthquake 15 km (9 mi) west of Fourpeaked and 25 km (16 mi) west-southwest of Mount Douglas at 15 km (9 mi) depth. This earthquake was immediately preceded by two foreshocks. A dozen small earthquakes occurred in this region in the 3 days before the ML=4.5. Another ML=4.5 earthquake occurred near Fourpeaked at 02:33 UTC (18:33 AKDT) on May 14, about 40 hours after the first earthquake. Comparison of the initial waveforms of the earthquake on seismograph station KABU suggests that both earthquakes had the same location and similar focal mechanisms. AVO analysts located 28 earthquakes in the 2 weeks following the second mainshock. It is unknown if this series of earthquakes are volcanic, but no observations of increased volcanic activity were received.\r\n   \"On May 19, a crew of Alaska Department of Fish and Game biologists reported steaming near Mount Douglas and Fourpeaked. AVO followed up on this report, noting that the lake at Mount Douglas froze over in previous years but did not freeze in 2013, which is likely the cause of the isolated report.\"","StartYear":2013,"StartMonth":4,"StartDay":null,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2013,"EndMonth":5,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Fourpeaked","ParentVolcano":"Fourpeaked","VolcanoID":"ak103","ParentVolcanoID":"ak103"},{"ID":713,"Name":"Cleveland 2013/5","Description":"From Dixon and others (2015): \"AVO continued to observe persistently elevated surface temperatures in satellite data (weather permitting) throughout the spring [of 2013]. At 12:59 UTC (04:49 AKDT) on May 4, the Okmok infrasound and seismic networks recorded an explosion from Cleveland. In response, AVO raised the Aviation Color Code and Volcano Alert Level to ORANGE/WATCH. A small ash cloud was first visible in satellite imagery at 13:48 UTC (06:48 AKDT). Over the next 3 hours, a small, detached cloud moved east and then southeast from the volcano and was last discernable about 200 km (125 mi) downwind. The explosion was followed by a period of infrasonic tremor interpreted as continuous low-level emissions (gas and [or] ash) from the vent. May 5 satellite images, including an unusual elevated temperature signal in AVHRR data, showed a small patch of ash at the Cleveland summit (fig. 41). Residents of Nikolski, 74 km (46 mi) away, reported a booming noise about 8:00 p.m. local time on the same day; however, no correlative explosion was detected with infrasound or other techniques.\r\n   \"On May 6, infrasound sensors and analysis of airwave signals detected three explosions from Cleveland (table 8 in original text). Satellite observations that day showed that the Cleveland summit crater filled nearly to the rim with tephra; the crater floor was marked by a 15 m (57 ft) diameter vent. New flowage deposits, including a lobe of lava (identified days later during reanalysis), extended down the upper northeastern, eastern, and southeastern flanks of the volcano. The lava flow lengthened over the next week, suggesting continued extrusion of lava from the summit vent. Details of the timing of lava extrusion with respect to explosions on May 6 remain unclear. Satellite images into June captured elevated temperatures in the summit area related to this activity (fig. 42 in original text).\r\n   \"Cleveland remained at Aviation Color Code and Volcano Alert Level ORANGE/WATCH until June 4, when AVO downgraded the status to YELLOW/ADVISORY. On July 26, analysis of a Landsat 8 image suggested new lava within the summit crater (fig. 43 in original text); it is possible extrusion of this lava occurred during a period of elevated temperatures and visible plume from the Cleveland summit during the prior week. AVO remained at YELLOW/ADVISORY and apparently this new lava never overtopped the crater rim, as it had in early May.\r\n   \"From early July through the end of 2013, AVO's infrasound and seismic networks detected a number of additional explosions and periods of infrasonic tremor at Cleveland (table 8 in original text). Most of these events did not have an accompanying ash signal in AVHRR satellite images, suggesting minor to no ash emissions during the events. It is entirely possible that very brief emissions of ash went unnoticed because of weather and gaps between satellite passes.\r\n   \"On December 28, a Cleveland explosion triggered the AVO infrasound alarms on both the Okmok and Akutan arrays at 21:29 UTC (12:29 AKST). Strongly elevated surface temperatures in the summit area appear in a satellite image 10 minutes prior to the explosion. Following a second explosion 2 days later, a small ash cloud was visible 73 km (45 mi) north of the volcano. Despite this activity, AVO remained at Aviation Color Code and Volcano Alert Level YELLOW/ADVISORY because these ash clouds were quite small, likely less than 20,000 ft ASL, and short-lived.\r\n   \"The 2013 activity at Cleveland is a continuation of the intermittent explosive and effusive activity that has occurred for much of the time since its last significant eruption in 2001 (Dean and others, 2004).\"\r\n   Cleveland began 2014 with three explosions generating minor ash plumes. Explosions were detected on December 28, December 30, and January 2. On January 2, citing increased explosions and minor ash plumes, AVO raised the Aviation Color Code and Alert Level to ORANGE/WATCH. Analysis of satellite, wind, and ash dispersion data indicates that the Dec 30 and Jan 2 plumes probably did not reach more than 15,000 ft above sea level. No new activity was observed after the January 2 explosion, and AVO lowered the Color Code/Alert Level to YELLOW/ADVISORY on January 10, 2014.\r\nOther than weakly elevated thermal anomalies in satellite imagery, no activity was observed at Cleveland until February 19, 2014 when a small steam plume was observed. On February 24, satellite data detected increased heat at Cleveland's summit. The following day, infrasound and lightning and alarms detected two small explosions at Cleveland Volcano at about 4:17 UTC February 25 (19:17 AKST February 24) and 10:35 UTC (1:35 AKST) February 25. Satellite data available several hours after these events occurred confirm that small ash clouds were generated by the explosions. The events were brief, and the estimated altitude of the drifting ash clouds was about 5 km (16,000 ft) asl. Satellite obsevations following the explosion show deposits of ash and large lava blocks on the upper flanks, extending 2.5 km (1.5 mi) from the summit. This suggests that these explosions were more energetic than those commonly observed over the past several years. However the ash emissions were brief and relatively low altitude, typical of recent Cleveland activity. The Color Code/Alert Level remained at YELLOW/ADVISORY.\r\nFrom Cameron and others, 2017: \"On March 6, residents of Nikolski village on the southwestern end of Umnak Island 73 km (45 mi) northeast of Cleveland reported dark ash rising from Cleveland at about 03:30-04:00 UTC on March 7 (6:30 or 7 p.m. AKST, March 6). In later discussions by telephone, residents further reported that, over a period of about 40 minutes, before the volcano became obscured by weather, alternating clouds of white steam and dark ash rose above the summit; the dark ash clouds rose about twice as high as white clouds but both dissipated quickly. Similar activity had been noted several months prior, so it is likely that other small episodes of ash emission have gone undocumented in the AVO database of eruptive activity from Cleveland during cloudy conditions \r\nwhen visual observations could not be made. The activity on March 6 was too ephemeral or small to be noted even in clear satellite views.\"","StartYear":2013,"StartMonth":5,"StartDay":4,"StartTime":"04:49:00","StartQualifier":null,"StartQualifierUnit":null,"EndYear":2014,"EndMonth":3,"EndDay":6,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":723,"Name":"Pavlof 2013/5","Description":"From Dixon and others (2015): \"Pavlof Volcano erupted in May 2013 and was characterized by Strombolian explosions and periods of continuous tremor. Eruption plumes deposited trace amounts of ash in nearby communities during the first 2 weeks of the eruption and again in early June. Activity and observations are summarized in table 7 [in original text]. Pavlof was upgraded from the Aviation Color Code and Volcano Alert Level of GREEN/NORMAL to ORANGE/WARNING on May 13, remaining at ORANGE/WARNING for 17 days during the 3-week-long eruption, with remainder of the time at YELLOW/ADVISORY. On August 8, the Aviation Color Code and Volcano Alert Level were downgraded to GREEN/NORMAL, where it remained for the rest of the year.\r\n   \"The 2013 eruption of Pavlof Volcano began on the morning of May 13, 2013, following a 6-year period of repose. Eruption onset was characterized by subtle, low-level seismicity beginning about 16:00 UTC (08:00 AKDT) and continuing for the first 24-48 hours of the eruption. A strong, persistent thermal signal from the Pavlof summit area was first observed in mid-infrared AVHRR satellite imagery at 15:17 UTC (07:17 AKDT) on May 13, and AVO upgraded the Aviation Color Code and Volcano Alert Level to ORANGE/WATCH, stating that an eruption was likely to progress. A pilot report at 03:00 UTC on May 13 (19:00 AKDT, May 14) confirmed the eruption, with numerous dark streaks on the upper northern flank of the volcano that appeared to be a lava flow and lahars initiated by melting of snow and ice in the summit area (fig. 28 in original text). Similar flows also were observed farther down the northern flank and that were initiated by the ejection of hot debris onto snow and ice. Residents of Sand Point, 85 km (53 mi) east of the volcano, reported seeing a distinctive glow at the summit of Pavlof during the evening of May 13, indicating likely lava fountaining. By the next day, satellite observations showed that a lava flow extending down the northern flank well beyond the summit vent. The flow was estimated to be about 600 m (2,000 ft) long and 30 m (100 ft) wide, and originated from a vent within a small crater just north of the summit.\r\n   \"AVO received numerous observations on May 14 confirming eruptive activity underway at Pavlof Volcano. Pilot reports and Web camera views of the volcano indicated that ash emissions as high as about 4 km (13,000 ft) ASL were occurring intermittently. Views of Pavlof, such as that in figure 29 [in original text], indicated several light-colored plumes rising off the lower northern flank, suggesting flowage of hot debris over ice and snow. Throughout the day on May 14, numerous strong bursts of tremor coincided with similar observations of large steam plumes rising off the northern flank of the volcano. Light-colored plumes from some of these events reached as high as 6 km (20,000 ft) ASL. Incandescence associated with strong lava fountaining at the summit also was observed throughout the evening of May 14. The lava fountaining was robust enough that relatively continuous infrasonic tremor was produced and recorded on infrasound arrays on Akutan Island (290 km [180 mi] southwest of Pavlof) and Okmok (460 km [285 mi] southwest of Pavlof) Volcanoes and at Dillingham (455 km [283 mi] northeast of Pavlof).\r\n   \"Noticeable fallout of fine ash occurred as far as 80 km (50 mi) downwind of the volcano on May 14, 15, and 18, and was reported to AVO. During May 15-20, sulfur dioxide (SO2) from Pavlof was detected in OMI satellite data; the estimated SO2 mass during May 15-16 was 1,000-2,000 metric tons and at least 4,000 metric tons on May 18-20 (Simon Carn, written commun., 2013). Sulfur dioxide also was detected on multiple days by the GOME-2 (Global Ozone Monitoring Experiment-2) and IASI (Infrared Atmospheric Sounding Interferometer) instruments.\r\n   \"From May 15 to 21, the eruption was characterized by nearly continuous tremor and explosions. A relatively continuous ash plume was apparent in AVHRR and MODIS satellite images and also was observed by pilots. Ash emissions during this period reached as high as 7 km (23,000 ft) ASL and extended about 400-500 km (250-310 mi) southeast of the volcano on May 18 (fig. 30 in original text). On May 19, trace amounts of ash fall occurred on the communities of Sand Point and Nelson Lagoon, 90 km (56 mi) southwest and northeast of Pavlof, respectively. AVO scientists examined an ash sample collected in Sand Point that consisted almost entirely of dark angular glass shards. A single electron microprobe analysis of the glass indicated that it is compositionally andesite (58 percent silicon dioxide, SiO2) and similar to ash deposits associated with previous historical eruptions (K. Wallace, USGS-AVO unpub. data; microprobe analyses by L. Hayden, USGS).\r\n   \"From May 22 to June 4, the volcano was relatively quiet, and the seismicity during this period was characterized by episodic, discrete bursts of tremor lasting from 30 seconds to approximately 1 minute. During May 22-23, the Pavlof seismic network detected distinct ground-coupled airwaves. Infrasonic arrays at Dillingham and Okmok Volcano also recorded these probable explosion signals as impulsive infrasonic waves.\r\n   \"From May 27 to June 4, seismic tremor and small discrete explosions were no longer detected in seismic and infrasound data. Satellite observations during this period showed no evidence of elevated surface temperatures, volcanic gas (SO2) or ash emissions. During periods of clear weather, no visual observations of ash emissions and Web camera views of the volcano were noted, indicating eruptive activity had paused. These observations prompted AVO to downgrade the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY at 20:50 UTC (12:50 AKDT) on May 27.\r\n   \"On June 4, 2013, AVHRR, MODIS, and GOES satellite data detected ash emission from Pavlof; passing pilots reported ash plumes as high as 5.7 km (18,700 ft) ASL. Slightly elevated levels of seismic tremor also were observed by midday (local) on June 4, roughly coincident with the observations of ash emissions, prompting an upgrade to ORANGE/WATCH at 12:15 UTC (20:15 AKDT). From June 14 to 19, seismic activity was characterized by periods of intermittent volcanic tremor and slightly more robust and more frequent explosions compared to the character of the seismicity from May 13 to 24. During this period, ash plumes generally were smaller and did not extend more than about 50 km (30 mi) downwind of the volcano. The maximum plume height reported by pilots was approximately 6 km (29,000 ft) ASL on June 10. Residents of Cold Bay reported barely perceptible trace ash fall during June 6-7.\r\n   \"From June 20 to 24, the Pavlof seismic network recorded moderate levels of relatively continuous tremor and small explosions. Several low-level ash plumes (generally less than 3.5 km or 11,500 ft) ASL were generated, although cloud cover occasionally inhibited observations.\r\n   \"Beginning around 07:00 UTC on June 25 (23:00 AKDT on June 24), tremor amplitudes at the volcano increased significantly and were characterized by high levels of continuous tremor and frequent explosions associated with robust episodes of lava fountaining and ash emission. The level of seismicity on June 25 was the strongest detected during the entire eruption. Observers in Sand Point reported incandescence and ash plumes as high as 6 km (20,000 ft) ASL on the morning of June 25, and around midnight on June 25, ash fall was reported in King Cove 50 km (30 mi) southwest of the volcano. Analysis of satellite images and pilot reports confirmed ash plumes as high as 7-8 km (23,000-26,000 ft) ASL. Sulfur dioxide emissions from Pavlof were detected by the Joint Polar Satellite System Ozone Monitoring Profiler Suite from 01:00 to 23:10 UTC on June 25. Automated analysis of this data indicated a mass of SO2 of 6,000-7,000 metric tons near the volcano. \r\n   \"Between June 25 and 27, intermittent ash plumes rose to 6 km (20,000 ft) ASL. After June 27, the seismicity became less energetic, and occasional low-frequency events and low levels of increasing discontinuous tremor characterized the seismicity. Pilot reports on June 28 indicated no activity at the volcano, and over the next several days, seismic tremor and small discrete explosions were no longer detected in seismic and infrasound data. Satellite observations after July 1 showed no evidence of elevated surface temperatures, volcanic gas, or ash emissions. On July 2, AVO downgraded the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY, where it remained until August 8 when the volcano returned to its normal background state and the Aviation Color Code and Volcano Alert Level were downgraded to GREEN/NORMAL.\r\n   \"The lahars and ash plumes generated during the eruption did not pose any serious hazards for the area. However, numerous local airline flights were cancelled or rerouted, and trace amounts of ash fall occurred at all local communities surrounding the volcano, including Cold Bay, Nelson Lagoon, Sand Point, and King Cove. Observations by AVO scientists during July 16-17 indicated that only the upper part of the Cathedral River drainage (fig. 31 in original text) had been inundated by lahars. However, a fountain-fed lava flow, about 5.8 km (3.6 mi) in length, covering an area of about 730,000 m2 (180 acres) on the northern flank of the volcano was observed (fig. 32 in original text). It was only possible to collect a few samples of the lava. These samples have not yet been analyzed (as of July 2015), but appeared similar to other andesitic lava flows produced by historical eruptions of Pavlof.\"","StartYear":2013,"StartMonth":5,"StartDay":13,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2013,"EndMonth":7,"EndDay":26,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Pavlof","ParentVolcano":"Pavlof","VolcanoID":"ak210","ParentVolcanoID":"ak210"},{"ID":733,"Name":"Veniaminof 2013/6","Description":"From Dixon and others (2015): \"Mount Veniaminof Volcano is a frequently active volcano on the Alaska Peninsula. From 2002 through 2010, nearly continuous low-level eruptive activity waxed and waned, producing wispy plumes that were reported by pilots, recorded on satellite images, and observed in images from the Federal Aviation Administration (FAA) Web camera in Perryville, 35 km (22 mi) east of the volcano. Activity ceased during the first one-half of 2013. In early June 2013, a several-day period of abrupt and gradually increasing levels of seismic tremor heralded the onset of a largely effusive eruption from the intracaldera cinder cone (table 6 in original text). Over the next 5 months, ash emissions and Strombolian explosions accompanied by five lava flows poured down the flanks of the active cone and advanced onto the surrounding ice-filled caldera. This eruption constructed a new spatter cone within the summit crater of the main active cone (Waythomas, 2013).\r\n   \"On June 7, 2013, gradually increasing, low-frequency tremor was recorded on two seismograph stations (VNWF and VNHG) as satellite images recorded elevated surface temperatures at the summit of the intracaldera cinder cone (fig. 10 in original text). The following day, June 8, in response to the continuing increase in seismic tremor, AVO upgraded the Aviation Color Code and Volcano Alert Level from GREEN/NORMAL to YELLOW/ADVISORY. Over the next several days, seismic tremor steadily increased. On June 13, seismicity levels and elevated surface temperatures at the summit of the cinder cone, as observed in satellite images indicated an eruption was likely underway. AVO issued a Volcanic Activity Notice (VAN) upgrading the Aviation Color Code and Volcano Alert Level from YELLOW/ADVISORY to ORANGE/WATCH. On June 14, ash deposits on the ice/snow-covered caldera floor were visible in satellite images, and the presence of lava on the cone was observed.\r\n   \"Clear weather provided good views from the FAA Web camera, located in nearby Perryville, as the eruptive activity increased and produced minor ash clouds (fig. 11 in original text). Satellite views on June 18 confirmed the Strombolian eruption and effusion of a 100 m (330 ft) wide lava flow (Flow 1; flow numbers refer to those identified in figure 12 [in original text] down the southwestern flank of the main cinder cone). Interaction of the lava with the caldera snow and ice field at the base of the main cone generated water-rich, ashy plumes (fig. 13 in original text). Clear satellite views the following day showed active flow lobes advancing over the ice at the base of the cone (fig. 14 in original text).\r\n   \"For the next couple of weeks, the activity continued with the southern flank flows (Flows 1 and 2) advancing and widening, with minor accumulations of ash on the caldera floor (figs. 15 and 25 in original text); Flow 2 descended east and adjacent to Flow 1, and Flow 3 advanced between and over the margins of Flows 1 and 2. The Strombolian eruption was visible in infrared satellite imagery, from the FAA Web camera in Perryville, and from several local lodges and remote camps (figs. 16 and 17 in original text).\r\n   \"On July 16, AVO geologist Chris Waythomas visited the caldera by helicopter, making observations and taking the first close-up photographs documenting the lava flows and ice cauldron formation (figs. 18 and 19 in original text). These close-up images of the vent area showed a new cone of accumulated spatter nested within the summit crater of the main cone.\r\n   \"By late July, the activity appeared to be waning as seismicity decreased, and reached a low level by August 2. In clear satellite views over this period, elevated surface temperatures were consistent with the still cooling, but no longer advancing, lava flow. On August 11, seismic tremor increased abruptly, and very high surface temperatures were observed in satellite images, suggesting that eruptive activity had resumed and lava again was flowing from the summit vent. Nighttime satellite images on August 12 confirmed lava erupting from the cone, and a clear morning view from the Perryville Web camera showed a minor ash column and cloud over the summit cone.\r\n   \"On August 18, AVO geologist Game McGimsey accompanied Ben Edwards, Dickinson University, on a National Geographic Society-sponsored visit to the caldera to document the ongoing activity, particularly the interaction of lava flows and the surrounding ice field. The southern flank lava flows had coalesced and largely melted into the ice, enlarging the ice cauldrons documented in July by Chris Waythomas, USGS/AVO (fig. 20 in original text). Steam rose from the margins where the hottest parts of the flows were still in contact with ice and water.\r\n  \"Strombolian explosions of incandescent lava and minor ash emissions were observed at the central active vent on August 18 (fig. 21 in original text). Two new lava flows issued either from tubes emerging from accumulations of spatter near the vent rim on the northeastern flank of the new cone, or from vents through the base of that cone. The flows descended to the ice field below, coalescing and forming another ice cauldron (fig. 22 in original text); forming Flow 4 (Waythomas, 2013). Voluminous steam generated by interactions of lava and ice/water obscured views into the cauldron. Forward Looking Infrared Radiometer (FLIR) images delineated the lava flows and hot spatter on the cone (fig. 22 in original text). As measured by the FLIR, maximum temperatures reached 700 to 800 degrees C.\r\n   \"Elongated lobes of sediment extended from the southern side of the ice cauldron, forerunners to the fifth and final lava flow of the eruption (figs. 23 and 24 in original text). Eruptive activity continued unabated for the next 12 days, and on August 30, AVO issued a VAN to report the intense seismicity, lava fountaining, and ash emissions as high as 15,000-20,000 ft (4,570-6,100 m) ASL. This marked the strongest unrest and eruptive activity since the eruption began in June. Satellite images on September 6 indicated further development of the lava flows on the northeastern flank (Flow 4), expansion of the main ice cauldron at its base, and creation of a second ice cauldron. A new lobe of the lava flow (Flow 5) also appeared in the satellite images, advancing southward from the main cauldron of Flow 4. The flow was captured in aerial photographs the following day (fig. 24 in original text). This flow continued to advance for possibly another week, but, by September 19, no evidence of active lava flows was observed in satellite images. Seismicity had begun to decrease during the week and the eruption appeared to be waning.\r\n   \"In response to the decrease in seismicity, and no evidence of eruptive activity in satellite and Web camera images, AVO issued a VAN on September 20 to downgrade the Aviation Color Code and Volcano Alert Level from ORANGE/WATCH to YELLOW/ADVISORY. An October 1 aerial image shows all five lava flows, partially snow covered, and only minor steam emissions from the summit vent (fig. 13 in original text).\r\n   \"On October 6, an abrupt increase in seismic tremor and the observation of highly elevated surface temperature indicated a resumption of lava effusion, and AVO responded by upgrading the Aviation Color Code and Volcano Alert Level to ORANGE/WARNING. No ash emissions were observed, and within a few days, seismicity began decreasing in what would be a downward trend coincident with the final end of eruptive activity in 2013. The Aviation Color Code and Volcano Alert Level were downgraded on October 17 to YELLOW/ADVISORY. Throughout the remainder of 2013, occasional elevated surface temperatures were observed in satellite images consistent with the cooling lava flows, and steam emission from the summit vent was visible on clear days in Web camera images.\r\n   \"The 2013 eruption of Veniaminof produced about 5 x 105 m3 of erupted lava, comparable in size to the 1983 eruption (Waythomas, 2013). A real-time seismic amplitude (RSAM) time series (Endo and Murray, 1991) from seismic station VNWF (fig. 11 in original text) is shown in figure 25 for the 5-month-long eruption, including significant eruptive events and color code changes (Waythomas, 2013). Before- and after-eruption views of the intracaldera cinder cone and geomorphic changes produced by the 2013 eruption are shown in figures 26 and 27 [in original text].\"\r\nFrom Cameron and others, 2017: \"The volcano gradually returned to a state of rest, and by early July 2014, seismicity had returned to normal background levels. AVO downgraded the Aviation Color Code and Volcano Alert Level to GREEN/NORMAL on July 9, 2014. Minor steam emissions and cooling of the lava flows continued intermittently for the remainder of the year. Several episodes of low-frequency events and tremor bursts occurred over the last one-half of the year (for example, July 15, October 8, December 18) as reported by AVO seismologists; however, these events were not associated with eruptive activity and are interpreted as continued degassing of the magmatic system.\"","StartYear":2013,"StartMonth":6,"StartDay":13,"StartTime":"05:25:00","StartQualifier":1,"StartQualifierUnit":"Days","EndYear":2013,"EndMonth":10,"EndDay":11,"EndTime":null,"EndQualifier":10,"EndQualifierUnit":"Days","Volcano":"Veniaminof","ParentVolcano":"Veniaminof","VolcanoID":"ak301","ParentVolcanoID":"ak301"},{"ID":1041,"Name":"Peulik 2013/6","Description":"From Dixon and others (2015): \"On June 18, AVO received a pilot report of 'smoke or steaming emerging from Mount Peulik,' but no anomalous activity was noted at the time of the report. On August 12, AVO received a second observation of unusual activity from a long-time guide in the area, reporting 'sulfur smell and lack of fish.' No similar reports were received and AVO did not investigate further.\"","StartYear":2013,"StartMonth":6,"StartDay":18,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2013,"EndMonth":7,"EndDay":12,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Peulik","ParentVolcano":"Ugashik-Peulik","VolcanoID":"ak212","ParentVolcanoID":"ak295"},{"ID":1111,"Name":"Great Sitkin 2013/7","Description":"From Dixon and others (2015): \"Two earthquake swarms were detected on seismic instrumentation at Great Sitkin Volcano during 2013, one in July and one in August. Both swarms consisted of about three dozen volcanic-tectonic earthquakes (fig. 46 in original text). Satellite data acquired September 3 showed a possible thermal feature, AVO determined that this was a signal from a known hot springs at the summit of Great Sitkin (fumarolic temperatures measured at 98 degrees C in 2005, Christina Neal, USGS/AVO, oral commun., 2013). The Aviation Color Code and Volcano Alert Level remained at GREEN/NORMAL throughout the year.\"","StartYear":2013,"StartMonth":7,"StartDay":null,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2013,"EndMonth":8,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Great Sitkin","ParentVolcano":"Great Sitkin","VolcanoID":"ak111","ParentVolcanoID":"ak111"},{"ID":1121,"Name":"Gareloi 2013/7","Description":"From Dixon and others (2015): \"In July and August [2013], AVO duty personnel responded to observations from a USFWS crew conducting ornithology work on Gareloi Island. The initial reports were of 'tremors of a magnitude that were noticeable to crews working outside, moving around.' A check of the seismicity showed no unusual activity. The background activity at Gareloi, since seismic station installation in 2003, has been constant low-level seismicity consisting of low-frequency earthquakes at a rate of one per minute. In light of the 2008 evacuation of a USFWS crew at Kasatochi and the subsequent eruption of Kasatochi (Waythomas and others, 2010), AVO closely monitored seismicity at Gareloi during the late summer. Despite close scrutiny, no changes were noted in the seismicity, nor were there further observations of felt events. Although the cause of the felt earthquakes was not determined, the felt reports were forwarded to AVO offices a week after a July 7 ML=5.5 earthquake and aftershock sequence south of Gareloi. The felt reports did not include event timing, and the most plausible explanation is that the USFW crew felt regional earthquakes and not volcano-related seismicity.\r\n   \"The USFW crew also noted 'steam coming from the extensive fumarole area on the west peak' on July 30. Although this was a single observation, the field crew additionally commented that the weather on July 30 was unusually clear and allowed for the observation of steaming (fig. 47 in original text). Steaming at fumaroles on Gareloi is routinely seen, with observations of steaming in 2003 and 2005 (Michelle Coombs, USGS/AVO, written commun., 2005).\"","StartYear":2013,"StartMonth":7,"StartDay":30,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2013,"EndMonth":7,"EndDay":30,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Gareloi","ParentVolcano":"Gareloi","VolcanoID":"ak106","ParentVolcanoID":"ak106"},{"ID":4161,"Name":"Iliamna 2014/1","Description":"From Cameron and others, 2017: \"Iliamna Volcano during 2014 experienced several significant rock/snow/ice avalanches on its eastern flank, and numerous smaller avalanches. Seismic data indicated a likely avalanche at 12:11 UTC (3:11 a.m. AKST) on January 28. This event was identified primarily by its characteristic seismicity - precursory seismicity of small, discrete events transitioning into a continuous signal consistent with a slide (Scott Stihler, UAFGI/AVO, written commun., 2014). In mid-May, satellite imagery of Iliamna showed recent avalanche deposits extending about 1.5 km (0.93 mi) eastward from a near-summit source area (Christina Neal, USGS/AVO, written commun., 2014) that may have been the source of the seismic signal 4 months earlier.\r\n\"AVO conducted its annual overflight of Iliamna to measure gas concentrations on April 10, recording normal background levels of about 32 tons/d of SO2. Because of an instrument malfunction, CO2 was not measured on this flight (Cynthia Werner, USGS/AVO, written commun., 2015). Iliamna remained at Aviation Color Code and Volcano Alert Level GREEN/NORMAL throughout 2014. \r\n\"On July 20, AVO received a phone call from a citizen on the Kenai Peninsula reporting a new avalanche at Iliamna, identified by the presence of new dark streaks within the snowfield. A review of the seismic data showed that the avalanche likely occurred at about 16:00 UTC (8:00 a.m. AKDT) on July 20. The deposit extended about 2.8 km (1.7 mi) east from the summit (Rick Wessels, USGS/AVO, written commun., 2014). \r\n\"Satellite imagery from August 19 documented new fresh avalanches at Iliamna, slightly larger than those in July. In early October, AVO observed evidence for a small, recent landslide or avalanche on the upper headwall of the Red Glacier on the eastern side of Iliamna. A retrospective analysis of the seismic data showed that the avalanche likely occurred in the early morning of October 3 (Jacqueline Caplan-Auerbach, Western Washington University, written commun., 2014). This new avalanche extended about 2 km (1.2 mi) from its source area.\"","StartYear":2014,"StartMonth":1,"StartDay":28,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2014,"EndMonth":10,"EndDay":3,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Iliamna","ParentVolcano":"Iliamna","VolcanoID":"ak124","ParentVolcanoID":"ak124"},{"ID":771,"Name":"Shishaldin 2014/1","Description":"From Cameron and others, 2017: \"In early 2014, Shishaldin Volcano began a low-level eruption that produced intermittent lava within the crater, low-level steam plumes, and occasional dustings of ash and ballistics on its upper flanks. This activity persisted from January 30 through the remainder of 2014. During the eruption, AVO monitored Shishaldin using the seismic array on Unimak Island, infrasound arrays at Akutan (135 km [84 mi] to the southwest) and Dillingham (582 km [362 mi] to the northeast), satellite imagery, a Web camera on adjacent Isanotski volcano looking northwest to Shishaldin, mariner observations, and pilot reports.\r\n\"Web and satellite imagery of Shishaldin Volcano showed persistent, low-level steam plumes beginning on January 17, although such activity is not unusual at Shishaldin. On January 30, satellite data showed increased surface temperatures in the summit crater, and AVO upgraded theAviation Color Code and Volcanic Alert Level to YELLOW/ADVISORY. Activity increased in early February, manifested by intermittent seismic tremor and airwave explosion signals recorded on distant infrasound instruments. On February 7, satellite data showed an ice-rich cloud at altitudes as high as 7,600 m (25,000 ft) ASL coming from Shishaldin, and AVO increased the daily watch schedule. Although this activity may have indicated a low-level eruption present in the summit crater, the eruption began no later than March 25, when satellite data indicated temperatures in the summit crater consistent with lava extrusion, and seismic and infrasound data recorded small explosions. On March 28, citing the inferred presence of lava in the summit crater, AVO upgraded the Aviation Color Code and Volcano Alert Level to ORANGE/WATCH. On March 30, 2014, a passing mariner photographed a darkened area at the crater rim, likely from a minor ash emission. \r\n\"Throughout April, seismic and infrasound stations continued to record intermittent explosion signals, and steaming often was visible in clear Web camera views. On April 26, AVO received a PIREP of a steam plume at Shishaldin at an altitude as high as 3,800 m (12,500 ft) ASL. Probable ash darkened the upper flanks of the summit crater in Web camera images taken on May 5. On May 13, AVO again observed elevated surface temperatures at the crater consistent with lava extrusion in the crater. One month later on June 14, a NASA Earth Observing-1 Advanced Land Imager (EO-1 ALI) image showed a dusting of ash on the snow around the summit crater. A mariner report on June 28 also described a slight dusting of ash on the snow, and satellite data from July 1, 17, and 27 showed fresh deposits of ash on the flanks of the edifice, suggesting persistent, low-level eruptive activity within the summit crater, consistent with heightened seismicity and elevated surface temperatures. \r\n\"AVO personnel conducting fieldwork photographed incandescence within the summit crater on August 10, 2014. Activity at Shishaldin remained remarkably consistent throughout August and September-elevated surface temperatures observed in satellite imagery, evidence of explosions from infrasound and seismic data, intermittent tremor, and occasional steam plumes viewed by pilots or in the Web camera. \r\n\"On October 1, satellite data again indicated temperatures within the summit crater consistent with extrusion of new lava. However, these elevated temperatures decreased by mid-October. Temperatures increased again on October 25, consistent with the reappearance of lava within the summit crater. This was accompanied by an increase in seismic tremor and explosions detected by infrasound. In response, AVO issued a Volcanic Activity Notice (VAN) on October 28 but the Aviation Color Code and Volcanic Alert Level remained at ORANGE/WATCH. After an apparent lull in eruptive activity between November 3 and November 20, the number and size of earthquake events at Shishaldin increased sharply, and AVO increased the watch schedule. At 10:00 UTC (1 a.m. \r\nAKST) on November 24, seismic activity again increased sharply, prompting AVO to issue another VAN at 10:49 UTC (1:49a.m. AKST) warning of a greater risk of ash emission outside the crater. For the next 2 days, surface temperatures increased and there was an increase in the number of seismic events and explosions detected by infrasound. A robust steam plume was observed in satellite imagery, but no significant ash deposition occurred outside the crater. This slightly elevated activity lasted 2 days, after which the usual low-level eruptive activity continued at Shishaldin into 2015.\"\r\n    In late January 2015, strongly elevated temperatures were observed in satellite images, consistent with active lava within the crater. A wispy, low-leve ash emission was observed in webcam images on February 2, 2015.\r\nThroughout February and March, 2015, clear satellite views often show elevated surface temperatures at the crater, seismicity remained above background, and low-level steam emissions were frequently seen in webcam images. It is likely that low-level eruptive activity continued within the summit crater. On April 16, 2015, several pilot reports of an ash plume at Shishaldin resulted in the issuance of an Ash Advisory SIGMET. No ash was visible in satellite and web camera images. Throughout April, and until at least the time of this writing (May 15, 2015), Shishaldin continued to show evidence of low-level eruptive activity, including elevated seismicity, elevated surface temperatures within the summit crater, and a visible steam plume. On May 8, observers from a  cruise ship in the area reported a steam/ash plume from Shishaldin, heading east. On the morning of May 15, a robust steam plume was detected in web camera views, possibly containing small amounts of ash.\r\nLow-level eruption continued at Shishaldin throughout May, 2015. On June 18, 2015, pilot reports and satellite imagery indicated a weak ash plume rising a few hundred feet from the summit crater; weak ash emissions continued on June 19, 2015. Elevated seismicity, with intermittently observed elevated surface temperatures continued at Shishaldin throughout June, July, August, September, and October. \r\nOn November 20, 2015,  AVO lowered the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY, because no elevated surface temperatures had been observed since October 19, 2015. Slightly elevated seismicity continued at Shishaldin, and robust steam plumes were often observed. \r\nOn March 10, 2016, AVO lowered the Aviation Color Code and Volcano Alert Level to GREEN/NORMAL, stating \"There has been an steady decrease in detected thermal activity at Shishaldin over the past several months. No anomalous activity has been observed in several clear satellite images of Shishaldin since moderately elevated surface temperatures were detected on January 13, 2016. Airwaves associated with low-level explosive degassing have not been detected in infrasound data since Feb. 7. Low-amplitude seismic tremor consistent with an open, degassing system system continues to be seen in seismic data and is considered to be within the bounds of background activity for Shishaldin.\"","StartYear":2014,"StartMonth":1,"StartDay":30,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2016,"EndMonth":1,"EndDay":16,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Shishaldin","ParentVolcano":"Shishaldin","VolcanoID":"ak252","ParentVolcanoID":"ak252"},{"ID":4231,"Name":"Tanaga 2014/2","Description":"From Cameron and others, 2017: \"In February and March 2014, an earthquake swarm occurred about 13 km (8 mi) southwest of Tanaga Volcano. This was the most energetic volcano-tectonic swarm at Tanaga since 2005 (McGimsey and others, 2007). The elevated seismicity continued into the summer, although at a reduced rate, and ended in late 2014. The swarm comprised 80 percent of all earthquakes located on or near Tanaga during the year. The earthquakes were all less than M2.0 and occurred at crustal depths of 5-10 km (3-6 mi). No specific cause was determined for the short-lived swarm. Despite the swarm, the Aviation Color Code and Volcano Alert Level remained at GREEN/NORMAL for all of 2014.\"","StartYear":2014,"StartMonth":2,"StartDay":null,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2014,"EndMonth":3,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Tanaga","ParentVolcano":"Tanaga","VolcanoID":"ak280","ParentVolcanoID":"ak280"},{"ID":4221,"Name":"Kanaga unrest 2014/3","Description":"From Cameron and others, 2017: \"A short lived swarm 5 km (3.1 mi) east-northeast of Kanaga Volcano began on March 26, 2014, with 24 located earthquakes. The number and size of earthquake doubled the next day, and included earthquakes with magnitudes up to 1.1. On March 27, the swarm started to decrease in numbers and intensity, and by March 29 had ceased altogether. The total swarm encompassed 72 earthquakes large enough to locate. Subsequent satellite observations showed no changes at the summit following this short-lived earthquake swarm. The only other notable observation of Kanaga seismic data was the presence of 2-3 Hz monochromatic signals in late August through early September, which could be a sign of magma moving under the volcano. The Aviation Color Code and Volcano Alert Level remained at GREEN/NORMAL for all of 2014.\"","StartYear":2014,"StartMonth":3,"StartDay":26,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2014,"EndMonth":3,"EndDay":27,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Kanaga","ParentVolcano":"Kanaga","VolcanoID":"ak144","ParentVolcanoID":"ak144"},{"ID":4171,"Name":"Novarupta 2014/5","Description":"From Cameron and others, 2017: \"Resuspension and transport of fine-grained volcanic ash from the Katmai National Park and Preserve region of Alaska frequently have been observed and documented for decades (Hadley and others, 2004; McGimsey and others, 2005), and five episodes of resuspended ash were documented in 2014. The 1912 eruption of Novarupta deposited large quantities of ash in valleys of the Katmai area, and the landscape remains desolate and largely vegetation-free, even more than a century later. During times of no snow and strong northwesterly winds, the ash can be resuspended and transported southeast across Shelikof Strait, Kodiak Island, and the Gulf of Alaska. These events commonly are identified by the presence of ash blowing from the Katmai area, often detected in satellite imagery, coupled with existing high winds and a lack of other volcanic signals (no thermal anomalies, no increased seismicity).\r\n\"On May 19, flights to Karluk on Kodiak Island were delayed because of weather conditions and a visible plume of resuspended ash originating from the Katmai area. The ash was weakly visible in satellite imagery, and strong northwesterly winds were blowing from the Katmai area towards the southeast. The National Weather Service Alaska Aviation Weather Unit (NWS AAWU) issued a Special Weather Statement. The NWS AAWU also issued SIGnificant METeorological information statements (SIGMETs) for resuspended Katmai ash due to strong winds on September 29 and October 5, when ash again was visible in satellite imagery blowing toward Kodiak Island. During the October 5 event, a citizen of Kodiak reported ash to AVO using via AVO’s \"Is Ash Falling\" system. Ash reached an altitude as high as 1,200-1,800 m (4,000-6,000 ft) ASL during the October 5 event.\r\nOn October 14, strong winds in the Katmai area once again picked up loose 1912 volcanic ash and carried it east over Shelikof Strait and Kodiak Island. The National Weather Service estimated the top of the cloud at an altitude of 1,200 m (4,000 ft) ASL. The NWS issued a Special Weather Statement, and AVO received a report of hazy conditions and trace ashfall (less than 1/32 in. deep) at Karluk on the southwestern side of Kodiak Island through AVO’s \"Is Ash Falling\" online ash reporting system. Federal Aviation Administration (FAA) Web camera images in Karluk also showed hazy conditions. AVO mentioned the resuspended ash event in the Friday, October 17, weekly update.\r\n\"The last ash resuspension event of 2014 occurred on Thursday, October 23, when strong winds resuspended 1912 volcanic ash and carried it southeast over Shelikof Strait, Kodiak Island, and the Gulf of Alaska. The ash was detected in satellite imagery, and the NWS issued Special Weather Statements, SIGMETs, and a Volcanic Ash Advisory. AVO \r\nincluded the ash resuspension event in its Friday, October 24, weekly update.\"","StartYear":2014,"StartMonth":5,"StartDay":19,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2014,"EndMonth":10,"EndDay":23,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Novarupta","ParentVolcano":"Novarupta","VolcanoID":"ak203","ParentVolcanoID":"ak203"},{"ID":851,"Name":"Pavlof 2014/5","Description":"From Cameron and others, 2017: \"The first eruptive episode at Pavlof in 2014 began at about 19:00 UTC (11 a.m. AKDT) on May 30, based retrospectively on a pulsating tremor-like signal in 1-5 Hz bandpass seismic data. The seismicity was visible across the Pavlof seismic network. By 07:22 UTC on May31 (11:22 p.m. AKDT, May 30), satellite data showed a strong thermal signal, suggestive of lava at the surface. AVO upgraded the Aviation Color Code and Volcano Alert Level from GREEN/NORMAL to ORANGE/WATCH at 19:36 UTC (11:36 a.m. AKDT) on May 31. Subsequent analysis indicated that the opening phase of the eruption on May 31 was recorded on an infrasound network on Akutan Island about 278 km (173 mi) southwest of Pavlof. AVO received the first pilot reports of ash emission on June 1, indicating distinct ash clouds as high as about 3km (2 mi) ASL, drifting north-northeast as much as 80 km (50 mi) beyond the summit of the volcano. Lahar (mud flow) signals were evident in seismic data from station PV6 by late in the day on June 1. These initial flows lasted for 15-30minutes each, and were preceded by sustained low-level pulsatory tremor.\r\n\"At about 01:30 UTC, June 3 (5:30 p.m. AKDT on  June 2) , the amplitude of the seismic tremor increased significantly; Web camera, satellite views, and several pilot reports all indicated that a period of robust ash emission was underway. At this point, AVO upgraded the Volcano Alert Level and Aviation Color Code from ORANGE/WATCH to RED/WARNING, where it remained for about the next 24 hours. During this period, the volcano erupted almost continuously, and observers in Cold Bay reported incandescence at the summit, seismic stations recorded lahar signals, seismic tremor remained at high levels, and strong thermal signals were evident in satellite data. The highest ash plume generated during this period of heightened activity reached as high as 6,700 m (22,000 ft) ASL (based on pilot reports) and extended about 100 km (60 mi) to the southeast over Sand Point and Unga Island. Although there were no reports of ashfall in nearby communities on June 2-3, significant SO2 emissions were detected in infrared atmospheric sounding interferometer (IASI) satellite data on June 3.\r\n\"Beginning at about 06:30 UTC on June 3 (10:30 p.m. AKDT on June 2), the overall level of seismicity began to decrease slowly, and at 01:54 UTC on June 4 (5:54 p.m. AKDT on June 3), AVO downgraded the Aviation Color Code and Volcano Alert Level to ORANGE/WATCH in response to the decreased levels of seismicity. Although the tremor level was reduced, the overall level of seismic activity remained relatively steady throughout the day on June 3, and was associated with a mostly steam-and-gas plume, containing only minor amounts of ash reaching as high as 5,900 m (19,600 ft) ASL and drifting to the south. Trace amounts of fine ash were reported at the Sand Point airport on June 3-4, resulting in cancelation of flights to Sand Point on the morning of June 4. As many as five flights to Cold Bay and nine flights to Dutch Harbor also were canceled on June 3-4 because of the risk of encountering ash. Local commuter air service was suspended as well during this time, affecting air travel to King Cove and False Pass. Flight cancellations continued into June 5, disrupting flights to and from Dutch Harbor and Cold Bay.\r\n\"The activity on June 2-3 was characterized by periods of vigorous lava fountaining that resulted in the accumulation of lava spatter on the upper northern flank of the volcano. This accumulation resulted in the formation of a spatter-fed lava flow that eventually extended about 4.7km (2.9 mi) downslope. At other times during the eruption, accumulations of spatter grew and built unstable piles of hot, fragmental material that occasionally collapsed and formed hot granular avalanches that flowed rapidly down the northern flank of the volcano for several kilometers. These hot granular rock avalanches swept across snow and ice, producing impressive steam plumes and generating melt water that led to the formation of lahars in some of the main drainages on the northern flank of the volcano. No ash or steam plumes were evident in satellite data after June 4, although seismic data recorded two explosions on the morning of June 5, and the World Wide Lightning Location Network (WWLLN) detected lightning near Pavlof from 10:16-10:59 UTC (2:16-2:59 a.m. AKDT) on June 5. Meteorological lightning is unusual in this part of Alaska, so the lightning likely was related to volcanic ash generated by the explosions. Emission of SO2 also was detected in OMI satellite data on June 5, and the SO2 plume extended from the volcano west about 100 km (60 mi).\r\n\"On June 6, the level of seismic activity decreased appreciably, relative to the previous several days. From June6-25, the level of unrest at the volcano continued to decrease further, and local observations of low-level lava fountaining were reported intermittently until about June 14. By June 25, satellite and Web camera data showed no evidence for lava fountaining or ash emissions. Only weakly elevated surface temperatures near the new lava flows on the northeastern flank were evident in satellite data. Consequently, AVO downgraded the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY on June 25. By July 29 (AKDT) seismicity at Pavlof had returned to its normal background status and AVO downgraded the Aviation Color Code and Volcano Alert Level to GREEN/NORMAL.\"","StartYear":2014,"StartMonth":5,"StartDay":30,"StartTime":"19:00:00","StartQualifier":null,"StartQualifierUnit":null,"EndYear":2014,"EndMonth":6,"EndDay":25,"EndTime":null,"EndQualifier":10,"EndQualifierUnit":"Days","Volcano":"Pavlof","ParentVolcano":"Pavlof","VolcanoID":"ak210","ParentVolcanoID":"ak210"},{"ID":4151,"Name":"Spurr 2014/6","Description":"From Cameron and others, 2017: \"A swarm of low-frequency earthquakes began in early June, following a M3.8 earthquake 13 km (8 mi) west of Mount Spurr. A total of 300 earthquakes were located in this swarm, which ended in mid-October. A swarm in the same area occurred in late 2012. The cause of the swarm remains undetermined. In 2004, seismicity, surface heat flux, and gas emissions suggested a magmatic intrusion (Power, 2004; Neal and others, 2005; Coombs and others, 2006).\r\n\"At 20:20 UTC (11:20 a.m. AKDT) on September 10, the Spurr seismograph network recorded a signal interpreted by AVO seismologists as a glacial outburst flood. The flow appears as a single event lasting about 20 minutes. Similar events, but of longer duration, have been recorded at Mount Spurr on several occasions, most recently in 2012 (Herrick and others, 2014). AVO was unable to visually confirm the inferred outburst event.\"","StartYear":2014,"StartMonth":6,"StartDay":null,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2014,"EndMonth":10,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Spurr","ParentVolcano":"Spurr","VolcanoID":"ak260","ParentVolcanoID":"ak260"},{"ID":861,"Name":"Cleveland 2014/6","Description":"After three months of no detected activity, an explosion occurred at Cleveland volcano at about 06:08 UTC, June 5, 2014, as detected on the Dillingham acoustic infrasound array and at seismic stations at Korovin Volcano. The event appears to have been of short duration and with similar amplitude to previous explosions at Cleveland. The Aviation Color Code and Alert Level remained at YELLOW/ADVISORY. No further activity was observed until weakly elevated surface temperatures seen in satellite data on July 7, 2014, and a vigorous steam and gas plume on July 8 and 9. In late July, 2014, clear satellite views showed persistently elevated surface temperatures in the summit crater, and typical gas and steam emissions. AVO field crews at Cleveland in August noticed typical steam and gas emissions from the summit. Elevated surface temperatures were again visible in satellite data in late August and early September. On September 11, AVO announced new monitoring capabilities at Cleveland: broadband and short-period seismometers, infrasound, and a webcam. Elevated surface temperatures and minor steaming continued at Cleveland throughout 2014. Satellite views in late November showed a small mound of lava in the summit crater, likely extruded around November 24, 2014. Seismicity remained at low levels.\r\nFrom Dixon and others, 2017: \"Cleveland began [2015] at Aviation Color Code YELLOW and Volcano Alert Level  ADVISORY and remained so for nearly 5 months. During this period, elevated temperatures were observed, as well as minor intermittent seismicity and steaming. At the volcano’s summit, the dome emplaced after the November 6, 2014, explosion remained the same size through February 2015. Elevated surface temperatures were observed in clear satellite images (fig. 22 [original text]). The diameter of the dome was about 45 m (150 ft) with an approximately 20 m (65 ft) depression that formed a shallow crater in the center. Incandescent fumaroles were detected on February 27 in cracks on the summit dome resulting from inflation of the dome. By March 27, satellite imagery confirmed growth of the dome to about 50 m (164 ft) in diameter (surface area 1,800 m2 or 19,000 ft2). \r\n\"After a sustained decline in eruptive activity over the span of a few weeks, Mount Cleveland was downgraded from Aviation Color Code/Volcano Alert Level YELLOW/ADVISORY to UNASSIGNED on May 28. Three weeks later, elevated surface temperatures returned, and a light dusting of ash visible on the upper flanks of Cleveland signified renewed activity. AVO increased the Aviation Color Code/Volcano Alert Level to YELLOW/ADVISORY on June 17 in response to this activity. Satellite imagery showed accelerated lava dome growth in the few days prior to raising the color code. The dome had increased to 55 × 85 m (180 × 280 ft) (outline area almost 3,900 m2 or 42,000 ft2). On July 21, the Aviation Color Code/Volcano Alert Level was elevated from YELLOW/ADVISORY to ORANGE/WATCH when an explosion at 16:17 UTC (08:17 AKDT) of similar amplitude as the explosion on November 6, 2014, at Cleveland was detected by the Cleveland infrasound array and ground-coupled airwaves on the Okmok seismograph network (fig. 23 [original text]). The explosion data, with no clear compression or rarefaction has been interpreted as a swelling and disruption of the conduit plug, followed by a more energetic 'uncorking' of the system (David Fee, UAFGI/AVO, written commun., 2015). This interpretation is similar to that for the previous explosion in November 2014. Satellite imagery showed that the lava dome was completely removed during this explosion and replaced by a small 40 m (130 ft) diameter crater. The hot summit vent surrounded by slightly cooler deposits likely from the July 21 explosion is shown in figure 24 [original text].\r\n\"On July 27 at 06:49 UTC (July 26 at 08:49 AKDT), a typical shallow subduction thrust earthquake of M=6.9 occurred about 80 km (50 mi) southeast from Cleveland. This earthquake was strictly tectonic and not related to the explosion at Cleveland, although many aftershocks were recorded on the Cleveland and neighboring seismograph networks.\r\n\"On July 30, strongly elevated surface temperatures were noted, consistent with dome growth after the explosion of the prior week. Two days later, on August 1 at 11:28 UTC (03:28 AKDT), a small airwave signal (40 times smaller than the July 21 explosion) in the region of Cleveland was detected, but was not considered a major explosion. Elevated surface temperatures were consistently observed in satellite imagery and a small steam plume was visible in the web camera following this small explosion. On August 4, AVO personnel overflew the summit of the volcano and observed a fresh lava dome forming that had a hot core (about 550-600 °C). Only \r\nminor degassing was detected during the flight. Images from this overflight are shown in figures 25A and B [original text]. \r\n\"A second explosion occurred on August 7 at 06:03 UTC (August 6, 22:03 AKDT) that was approximately one-half the amplitude of the July 21 explosion and much shorter in duration (1-2 seconds; fig. 26 [original text]). As viewed from satellite imagery, the lava dome that had been growing steadily since July 21 was only partially removed along its southern margin. On August 15, another overflight of the summit by AVO personnel showed more robust degassing and a dome with extrusions of partially new lava (\r\nfig. 25 [original text]; Werner and others, 2017). Satellite data from August 14 show that the 80m (262 ft) diameter lava dome deflated in the center and a 25-30 m (82-98 ft) diameter area of incandescent fractures across the dome surface was observed.\r\n\"August 29 marked the first notable earthquake swarm since the installation of a seismograph network on Cleveland in the summer of 2014 (fig. 27 [original text]). The swarm began around 19:03 UTC (11:03 AKDT) and continued for several hours before diminishing. This earthquake swarm was concurrent with elevated surface temperatures; however, nothing of note was recorded in the infrasound data. \r\n\"Elevated temperatures and minor steaming persisted for a few weeks following the two explosions. Strongly elevated temperatures decreased after July 30 and moderately elevated temperatures decreased regularly after that. This led to a lowering of the Aviation Color Code/Volcano Alert Level from ORANGE/WATCH to YELLOW/ADVISORY on October 14, and Cleveland remained at this level for the remainder of the year. Intermittent weakly elevated surface temperatures and minor steaming characterized the activity \r\nfor the latter months of the year. A summary of the eruption between 2011 and 2015 is shown in figure 28 [original text].\"","StartYear":2014,"StartMonth":6,"StartDay":5,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2015,"EndMonth":8,"EndDay":18,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":881,"Name":"Semisopochnoi 2014/6","Description":"From Cameron and others, 2017: \"Low-frequency events at Semisopochnoi Island were first noted on June 1, 2014. Semisopochnoi's seismic network had been returned to service on May 22, 2014, only 2 weeks prior to these events. The swarm began on June 9 at about 18:00 UTC (10:00 a.m. AKDT), and the AVO network recorded about 40 volcanic-tectonic earthquakes over the next 2 days. These earthquakes were small (less than M2) and clustered around Mount Cerberus in the center of the caldera. Depths ranged from 2 to 10 km (1.2 to 6.2 mi).\r\n\"Tremor was first noted on June 12, coincident with an increase in the rate of earthquakes recorded. Over the next day, the number of earthquakes doubled over the total located in the previous 3 days. The number of located earthquakes, all volcano-tectonic, doubled again on June 14, marking the peak daily earthquake count of the sequence (223 earthquakes). Throughout the increase in activity, the depth range of the events and epicentral area did not change. On June 13, AVO issued a VAN upgrading the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY based on the ongoing swarm . Following the peak in earthquake activity on June 14, the number of located events decreased to 20-30earthquakes located in the last week of June, and further decreases in seismicity continued into July and August.\r\n\"On June 23, a M7.9 earthquake occurred in the region, 73 km (46 mi) west of Semisopochnoi Island at a depth of 118 km (73 mi) in the subducting slab. It was accompanied by more than 2,500 aftershocks, 60 with magnitudes of 4.0 or greater. There was no direct causality between the M7.9 earthquake and the Semisopochnoi volcanic-tectonic earthquake (VT) swarm; AVO did not note any change in the rate of VT seismicity at Semisopochnoi following the M7.9 earthquake.\r\n\"Zhong Lu of Southern Methodist University evaluated the deformation related to the volcanic unrest. More than 10 cm (4 in.) of inflation occurred between 2003 and June 26, 2014, about one-half of which occurred between June 15 and June 26, 2014. Maximum uplift was approximately in the center of the caldera. Modeled source depth ranges from 5 to 10 km (3 to 6 mi). (Zhong Lu, written commun., 2015).\r\n\"The consensus interpretation of the 2014 swarm is that it represents an intrusion of magma. This would be consistent with the style and character of the seismic swarm as well as the deformation signal. Although the seismograph network was not operational before May 22, the absence of significant activity between May 22 and June 9 suggests that the intrusion occurred in mid-June. An earlier pulse of magma possibly was emplaced before May 22, but without an operational seismograph network, this cannot be verified.\r\n\"In response to the swarm, AVO instituted heightened seismic watch schedules, requested that NOAA initiate HYSPLIT model ash cloud trajectory runs, and solicited pilots and the U.S. Coast Guard to report any unusual volcanic activity (such as steaming or ground cracks). Daily satellite analysis by AVO staff included careful examination of the volcano using all available imagery. Throughout the sequence, no surface activity was noted in the few clear-weather views of the island. The volcano is remote, and aerial reconnaissance by AVO staff was determined to be too costly to obtain.\r\n\"The 2014 unrest was the first significant departure from background at Semisopochnoi since installation of the seismic network in 2005. Background seismicity at Semisopochnoi had been relatively low (fewer than 50 earthquakes located per year until 2014), with short periods of weak seismic tremor. The last confirmed eruption at Semisopochnoi was from a satellitic vent in 1987 (Miller and others, 1998). The volcano, however, was deforming. Lu and Dzurisin (2014) discovered an area about 2 km (1.2 mi) in diameter that subsided during 2004-2010 at a rate of about 10 mm/yr (0.4in/yr). They suggested compaction of young volcanic deposits in the caldera as a mechanism to explain this subsidence; alternative hypotheses include localized subsidence due to depressurization of a shallow hydrothermal system or localized changes in the groundwater table.\"","StartYear":2014,"StartMonth":6,"StartDay":13,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2014,"EndMonth":8,"EndDay":4,"EndTime":null,"EndQualifier":1,"EndQualifierUnit":"Months","Volcano":"Mount Young","ParentVolcano":"Semisopochnoi","VolcanoID":"ak44","ParentVolcanoID":"ak248"},{"ID":4181,"Name":"Martin 2014/10","Description":"From Cameron and others, 2017: \"Beginning on October 7, the AVO seismic network recorded an earthquake swarm centered roughly 15 km (9.3 mi) northwest of Mount Martin in an area where about 10 earthquakes per year are recorded. Twenty-six earthquakes were recorded on October 7, and, over the next 5 days, a total of 40 earthquakes were recorded. The largest earthquake in the swarm was a M1.8 on October 7. Seismicity in the Katmai region is dominated by earthquakes at volcanic centers; this swarm occurred in an established cluster of seismicity, closest to Mount Martin. The cluster of seismicity is dominated by shallow (less than 10 km [6.2 mi] deep) earthquakes with calculated magnitudes less than M2. No specific cause has been identified for the long-lived seismicity at this location.\r\n\"On November 24, observers in King Salmon emailed AVO about robust steam plumes rising about 300 m (about 1,000 ft) above Mount Martin. Observers reported that the plumes continued until the evening of November 25, after which they were no longer visible from King Salmon. These fumarolic vapor plumes are common at Mount Martin (McGimsey and Neal, 1996; McGimsey and Wallace, 1999; Neal and others, 2005; McGimsey and others, 2007; Herrick and others, 2014).\"","StartYear":2014,"StartMonth":10,"StartDay":7,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2014,"EndMonth":11,"EndDay":24,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Martin","ParentVolcano":"Martin","VolcanoID":"ak189","ParentVolcanoID":"ak189"},{"ID":971,"Name":"Pavlof 2014/11","Description":"From Cameron and others, 2017: \"Pavlof remained quiet and at background levels of seismicity until November 12, when seismic tremor increased sharply and increased surface temperatures were detected in satellite data, suggesting that lava had reached the surface. This was corroborated by reports of minor ash emissions and low-level lava fountaining from observers in Cold Bay. Observers also reported flows of rock debris and ash descending the northern flank of the volcano, and incandescence was observed in Web camera images. As a result of these observations, AVO upgraded the Aviation Color Code and Volcano Alert Level to ORANGE/WATCH on November 12.\r\n\"After November 12, the level of seismic activity continued to increase gradually and the thermal signal at the summit became persistently visible in satellite data. On November 13, satellite data showed a 200-km-long (124-mi-long) ash plume extending northwest of the volcano.Pilot reports estimated the ash cloud top at about 2,400-2,700m (about 7,900-8,900 ft) ASL. For the next 24 hours, all Pavlof seismic stations recorded nearly continuous seismic tremor, and satellite data showed strongly elevated surface temperatures, consistent with sustained lava fountaining. A narrow ash plume extending as high as 200 km (124 mi) from the volcano continued to be visible in satellite data, and information from passing pilots indicated that the ash plume eventually reached an altitude of about 4,800 m (15,700ft) ASL. Minor SO2 emissions were detected on November 14 in satellite data.\r\n\"On November 15, the intensity of seismic tremor increased significantly over a 6-hour period and satellite data indicated that the ash cloud, visible for the previous several days, had expanded and reached an altitude of about 7,600m (25,000 ft) ASL, and extended at least 200 km (124 mi) northwest of the volcano. In response to this increase in eruptive activity, AVO upgraded the Aviation Color Code and Volcano Alert Level to RED/WARNING. This plume eventually reached an altitude of at least 11,000 m (36,000ft) \r\nASL and extended about 385 km (240 mi) northwest of the volcano. Although the volcano was obscured by clouds, observers in Cold Bay reported rumbling and thunder-like sounds coming from the direction of Pavlof Volcano. Infrasonic tremor levels detected by the infrasound array in Dillingham increased steadily through the day on November 15 and were as high as, or higher than, infrasound levels recorded at any time during Pavlof’s May-June 2014 or 2013 eruptions (David Fee, UAFGI/AVO, written commun., 2014). The SO2 plume generated by this phase of the eruption extended west over the Bering Strait and into eastern Russia.\r\n\"Seismicity at the volcano decreased significantly on November 16 and remained at low levels, and ash plumes were not observed in satellite data thereafter. In response to thedecrease in seismicity and ash emission, AVO downgraded the Aviation Color Code and Volcano Alert Level to ORANGE/WATCH on November 16.\r\n\"Satellite observations indicated that eruptive activity ceased by about November 17. The intensity of thermal signals decreased gradually and the levels of tremor fluctuated slightly, but the overall amplitude decreased steadily. Thermal signals were occasionally observed in satellite datathrough November 26, but were the result of the still hot lava and debris on the northern flank of the volcano. As a result of the diminished levels of unrest, AVO downgraded the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY on November 26, UTC (November 25, AKST). \r\n\"No further eruptive activity occurred at Pavlof Volcano in 2014, although unstable accumulations of cooling lava spatter occasionally collapsed, generating small ash emissions. The volcano gradually returned to normal background status, and on January 15, 2015, AVO downgraded the Aviation Color Code and Volcano Alert Level to GREEN/NORMAL.\"","StartYear":2014,"StartMonth":11,"StartDay":12,"StartTime":"15:00:00","StartQualifier":null,"StartQualifierUnit":null,"EndYear":2014,"EndMonth":11,"EndDay":17,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Pavlof","ParentVolcano":"Pavlof","VolcanoID":"ak210","ParentVolcanoID":"ak210"},{"ID":991,"Name":"Semisopochnoi 2015/1","Description":"From Dixon and others, 2017: \"An increase in seismicity at Semisopochnoi was recorded in January 2015, characterized by numerous small earthquakes, most with magnitudes less than ML=1. The seismicity continued for several months and when tremor associated with the earthquake swarm appeared, AVO raised the Aviation Color Code/Volcano Alert Level from UNASSIGNED to YELLOW/ADVISORY on March 25, 2015. After a decline in the seismicity over a period of several months, the Aviation Color Code and Volcanic Alert Level were downgraded to UNASSIGNED on May 28. Throughout the earthquake swarm, no deformation or associated thermal anomalies were observed.\"","StartYear":2015,"StartMonth":1,"StartDay":null,"StartTime":null,"StartQualifier":14,"StartQualifierUnit":"Days","EndYear":2015,"EndMonth":4,"EndDay":null,"EndTime":null,"EndQualifier":1,"EndQualifierUnit":"Months","Volcano":"Mount Young","ParentVolcano":"Semisopochnoi","VolcanoID":"ak44","ParentVolcanoID":"ak248"},{"ID":4281,"Name":"Novarupta 2015/3","Description":"From Dixon and others, 2017: \"High winds entrained and resuspended ash from Novarupta-Katmai 1912 on March 11, 2015, continuing into March 12, 2015. Alaska Airlines and Ravn Alaska cancelled flights into and out of Kodiak, due to high winds and ash. The ash was visible in satellite imagery, and strong winds were blowing from the Katmai area toward the southeast (fig. 7 [original text]). The National Weather Service Alaska Aviation Weather Unit (NWS AAWU) issued a Special Weather Statement. \r\n\"Four episodes of resuspended ash were observed during August through October. A multi-day ash resuspension event began on August 28, 2015, and continued through August 31, 2015. On August 30, the NWS issued a SIGnificant METeorological (SIGMET) information statement, and AVO mentioned the resuspended ash in its August 28 weekly update and issued a separate information statement on August 31. The ash was weakly visible in satellite imagery. Two ash resuspension events occurred in September-on \r\nSeptember23, with ash confined to altitudes less than 1,500 m (5,000ft) ASL, and another on September 29-30. \r\nResidents of Kodiak reported a fall of fine ash on the night of September 29-30, mixed with sleet and snow. AVO issued information statements on both occasions. The final ash resuspension event of 2015 occurred on October 29-30, when strong winds in the Katmai area again entrained loose 1912 volcanic ash and carried it east over Shelikof Strait and Kodiak Island. AVO again issued an information statement regarding the event.\"","StartYear":2015,"StartMonth":3,"StartDay":11,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2015,"EndMonth":10,"EndDay":30,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Novarupta","ParentVolcano":"Novarupta","VolcanoID":"ak203","ParentVolcanoID":"ak203"},{"ID":4301,"Name":"Kupreanof 2015/4","Description":"From Dixon and others, 2017: \"A mariner report of 'black smoke northwest of Ivanof Bay' was received at AVO on April 11, 2015. The probable source of the observation is Kupreanof Volcano where a known fumarolic field has persisted for decades (Yount and others, 1985b). Although reports from Kupreanof are uncommon, steaming from Kupreanof has been noted for at least the last 75 years and was last reported in the AVO annual summaries in 1994 (Neal and others, 1995). AVO took no further action on this isolated report.\"","StartYear":2015,"StartMonth":4,"StartDay":11,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2015,"EndMonth":4,"EndDay":11,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Kupreanof","ParentVolcano":"Kupreanof","VolcanoID":"ak175","ParentVolcanoID":"ak175"},{"ID":4251,"Name":"Spurr 2015/7","Description":"From Dixon and others, 2017: \"No volcanic activity was reported at Mount Spurr in 2015; the only activity noted was an earthquake swarm 12 km (6.5 mi) north of the summit. First noted in the AVO internal logs in mid-October, earthquakes in this area occurred sporadically for the previous 5 months with the rate increasing from 1-2 per week in July to several per day in October. The swarm peaked in November, with 47 earthquakes during the month. The rate of located earthquakes decreased by one-half in December and the swarm continued into 2016 at a much-reduced level of activity. The earthquakes in this cluster were shallow with 90 percent occurring between 3 and 5 km (1.6 to 2.7 mi) below sea level. The Aviation Color Code and Volcano Alert Level remained at GREEN/NORMAL through the year at Spurr.\"\r\nIn 2016, there were four distinct clusters of seismicity at Spurr: \"the typical Mount Spurr summit earthquakes that occurred throughout the year, earthquakes near Pothole Glacier (west of Mount Spurr) in late summer, an ongoing swarm of low-frequency earthquakes 10–15 km (6–9 mi) north of the summit (north Spurr earthquakes in fig. 5), and a cluster of earthquakes located 5 km (about 3 mi) east of the summit in May (east Spurr earthquakes in fig. 5). In addition to these areas of high activity, there are three, less-distinct zones of activity. These zones are 10 km (6.2 mi) south, 5 km (3 mi) west, and 20–30 km (12–18.5 mi) northeast of Mount Spurr and are in the area of the 1996 Strandline earthquake (Kilgore and others, 2011). The Aviation Color Code and Volcano Alert Level remained at GREEN and NORMAL, respectively, throughout the year for Spurr.\" (Cameron and others, 2020).\r\nDixon and others (2020) report the seismicity at Spurr continued into 2017, including the unusual earthquake sequence that began in 2015. \"This cluster of low-frequency earthquakes (north Spurr earthquakes), was located 12 kilometers (km; 7 mi) north of Mount Spurr and continued to show activity throughout 2017. Although the character of the earthquakes is similar to glacial earthquakes, AVO has not determined a definite cause for this cluster of seismicity. The other four clusters (Mount Spurr summit, south Spurr, west Spurr, and the Strandline Lake earthquakes) are typical seismicity seen year-round in the vicinity of Mount Spurr (fig 2). An April 20 gas observation flight noted that the small plume emanating from the fumaroles in Spurr’s summit crater contained detectable quantities of SO2, H2S, and HCl. The Aviation Color Code and Volcano Alert Level remained at GREEN and NORMAL throughout the year at Mount Spurr.\"","StartYear":2015,"StartMonth":6,"StartDay":null,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2017,"EndMonth":null,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Spurr","ParentVolcano":"Spurr","VolcanoID":"ak260","ParentVolcanoID":"ak260"},{"ID":4261,"Name":"Redoubt 2015/6","Description":"From Dixon and others, 2017: \"A significant amount of melt water was observed in late June, a suspected outburst flood from a subglacial meltwater reservoir in the Redoubt Volcano crater. Ground investigations determined the source of this outburst flood to be melt from a snow and debris avalanche, similar to those that routinely occur on Iliamna Volcano (fig. 4 [in original text]). A review of web camera views indicates this event occurred after June 28, and seismic evidence suggests a start at 03:54UTC (19:54 AKDT) June29. The source of the avalanche was a steep canyon wall immediately west of the 2009 dome. The avalanche is composed of multi-year snow and ice entrained with rock debris and fragmental products of the 2009 eruption. The Aviation Color Code and Volcano Alert Level were not changed due to this outburst flood and remained at GREEN/NORMAL through the year.\"","StartYear":2015,"StartMonth":6,"StartDay":29,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2015,"EndMonth":6,"EndDay":29,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Redoubt","ParentVolcano":"Redoubt","VolcanoID":"ak231","ParentVolcanoID":"ak231"},{"ID":1141,"Name":"Veniaminof 2015/10","Description":"From Dixon and others, 2017: \"Mount Veniaminof had a 2-month-long period of increased seismic unrest in 2015. At the end of September, seismicity at Mount Veniaminof increased in the form of volcanic tremor and small low-frequency earthquakes. This type of activity was a known precursor to previous eruptions, most recently in 2009 (McGimsey and others, 2014) and 2013 (Dixon and others, 2015). On October 1, after the activity persisted for 1 day, the Aviation Color Code and Volcano Alert Level were raised to YELLOW/ADVISORY. Throughout October and early November, clear views from the Federal Aviation Administration (FAA) Perryville northwest web camera occasionally showed minor steam plumes issuing from the intracaldera cone (fig. 11[original text]). The intermittent, short bursts of seismic tremor persisted into November, indicating continued unrest. At the end of November, the seismic unrest at Veniaminof decreased to near background levels. On December 11, the Aviation Color Code and Volcano Alert Level was lowered to GREEN/NORMAL.\"","StartYear":2015,"StartMonth":10,"StartDay":1,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2015,"EndMonth":11,"EndDay":null,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Veniaminof","ParentVolcano":"Veniaminof","VolcanoID":"ak301","ParentVolcanoID":"ak301"},{"ID":4731,"Name":"Makushin unrest 2016","Description":"From Cameron and others (2020): \"Earthquake swarms are common at Makushin Volcano, and nine short earthquake swarms occurred in 2016. Most swarms comprised fewer than two dozen earthquakes each. Prominent swarms occurred on February 7, April 12, August 26, September 21, September 24, November 15, November 27, and December 26 (fig. 26). During all of 2016, the Aviation Color Code and Volcanic Alert Level remained at GREEN and NORMAL respectively.\"","StartYear":2016,"StartMonth":2,"StartDay":7,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2016,"EndMonth":12,"EndDay":26,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Makushin","ParentVolcano":"Makushin","VolcanoID":"ak188","ParentVolcanoID":"ak188"},{"ID":1151,"Name":"Pavlof 2016/3","Description":"From Cameron and others (2020): \"Pavlof Volcano erupted on March 27, 2016, about 500 days after the end of the previous eruption in 2014 (table 5). The March 27-28 eruption was a brief but intense eruptive event lasting about one day (fig. 16). This event generated minor ashfall at Nelson Lagoon 77 km (48 mi) northeast of Pavlof Volcano and trace ashfall at Port Heiden and Dillingham 263 km (164 mi) and 453 km (281 mi) northeast of Pavlof, respectively. More than a hundred flights were cancelled between March 27 and March 29 because of ash from the eruption. Two additional eruptive periods occurred in May and July 2016, but these events produced only small ash clouds and minor ash fallout confined to the upper flanks of the volcano. The March 28 eruption generated significant ash clouds reaching as high as 12.5 km (41,000 ft) ASL, and pyroclastic flows and lahars on the flanks of the volcano, one of which destroyed seismic station PV6 on the north flank of the volcano.\r\n\"The first indication of unrest in 2016 began with a late morning telephone call on March 25 from National Weather Service personnel in Cold Bay, Alaska, who reported a steam plume rising from the summit of Pavlof Volcano (fig. 17). Although steam plumes at Pavlof are common, this particular plume was reported as more robust than usual. A review of web camera images from a Federal Aviation Administration (FAA) web camera in Cold Bay showed a prominent steam plume visible from 17:47 until 19:57 UTC (9:47 to 11:57 AKDT), when it became obscured by clouds. No unusual seismic activity was noted on March 25 or the following day on March 26.\r\n\"The volcano remained quiet throughout most of the day on Sunday, March 27, and a relatively clear satellite view of the volcano summit above the cloud deck at 22:33:15 UTC (14:33 AKDT) showed no evidence of any unrest. At 00:18 UTC, March 28 (16:18 AKDT), an ash cloud reaching about 6 km (20,000 ft) ASL and moving north was reported by a nearby pilot. At about 01:33 UTC March 28 (17:33 AKDT March 27), AVO received a pilot report of ash emissions from Pavlof Volcano reaching an altitude of about 9.1 km (30,000 ft) ASL and observations of lava at the surface. Retrospective analysis of seismic data indicated that seismicity began to increase from background levels at about 23:53 UTC (15:53 AKDT) denoted by an abrupt increase in real-time seismic amplitude measurement (RSAM) levels and the appearance of continuous tremor on all operating stations of the Pavlof Volcano network. The tremor and RSAM levels observed on station PS4A illustrate seismicity during the eruption (fig. 18). At about 00:00 UTC March 28 (16:00 AKDT) tremor and RSAM levels continued to increase until about 06:38 UTC March 28(22:38 AKDT) after which the RSAM values leveled off but continued to fluctuate. At approximately 09:46 UTC March 28 (01:46 AKDT) they increased toward a peak value of 3200 and then began to decline in a saw tooth pattern until 20:40 UTC (12:40 AKDT) when the values fell to about pre-eruption levels (fig. 18).\r\n\"The abrupt increase in RSAM and tremor observed around 00:00 UTC March 28 (16:00 AKDT March 27) prompted AVO to raise the Aviation Color Code and the Volcano Alert Level to RED and WARNING at 01:12 UTC March 28 (17:12 AKDT), respectively. The rapid increase in seismicity is characteristic of several recent Pavlof Volcano eruptions, and it is not uncommon for the Aviation Color Code and the Volcano Alert Level to move from background status to the highest level with minimal precursory seismic activity.\r\n\"At 04:05 UTC March 28 (20:05 AKDT March 27), AVO received a pilot report of lava fountaining near the summit and a flowage feature on the north flank of the volcano. According to the pilot, the flowage feature had apparently reached the Bering Sea coast. The pilot referred to the feature as a pyroclastic flow, and it is possible that pyroclastic flows produced by collapse of the eruption column formed during the eruption. It is also possible that meltwater generated by the interaction of pyroclastic flows with snow and ice may have flowed well beyond the volcano to the north as lahars. The specific drainage containing the flow was not identified by the pilot, but lahars from previous historical eruptions have inundated both the Leontovich and Caribou River drainages on the north side of Pavlof Volcano.\r\n\"Pyroclastic flows or hot granular mass flows associated with collapse of spatter accumulations on the upper part of the edifice likely destroyed seismic station PV6 on the lower north flank of the volcano (fig. 19). Flowage signals were evident at PV6 starting about 01:06 UTC March 28 (17:06 AKDT March 27), and the station stopped transmitting 12 minutes later at 01:18 UTC March 28 (17:18 AKDT March 27).\r\n\"Satellite observations from 04:15 UTC March 28 (20:15 AKDT March 27) indicated that the ash cloud from the eruption extended 180 km (108 mi) northeast beyond the volcano over the Bering Sea (fig. 20). Ash cloud heights from pilot reports indicated a maximum altitude of about 9.1 km ASL (30,000 ft). By 15:10 UTC March 28 (07:10 AKDT), the Pavlof Volcano ash cloud formed a narrow, continuous plume that extended for about 885 km (550 mi) from the volcano over interior Alaska as detected in a Himawari-8 false color image (fig. 21).\r\n\"Ash fallout on March 27–28 was reported in several communities northeast of Pavlof Volcano, including Nelson Lagoon, Port Heiden, and Dillingham, Alaska. In Nelson Lagoon 77 km (48 mi) northeast of Pavlof, 3–17 millimeters (mm; 0.125–0.66 inches) of dark ash fell, covering roofs and surfaces (fig. 22). Trace amounts of ash (\u003c0.8 mm) were reported in Port Heiden and in Dillingham 263 km (164 mi) 453 km (281 mi) northeast of Pavlof Volcano, respectively.\r\n\"The March 27-28 ash plume caused the cancellation of 41 Alaska Airlines flights to and from Barrow, Bethel, Anchorage, Fairbanks, Kotzebue, Nome, and Prudhoe Bay, Alaska, on Monday, March 28, 2016. Regional flights operated by Bering Air were cancelled on the morning of March 28, PenAir suspended service to Dutch Harbor, Alaska, in the afternoon, and Ravn reported numerous flight cancellations (FOX59, 2016). Flight cancellations continued on Tuesday, March 29, and Alaska Airlines reported 28 cancelled flights to Barrow, Bethel, Kotzebue, Nome, and Prudhoe Bay, representing about 57 percent of Alaska’s flights to the most northern region it serves. Alaska Airlines additionally reported more than 6,200 travelers were affected on March 28 and 29 (Alaska Airlines, 2016).\r\n\"Lightning in the vicinity of Pavlof Volcano was reported by the WWLLN, which consisted of 16 lightning flashes detected over a 6-hour period between 13:10-19:13 UTC (05:10–11:13 AKDT) on March 28. Sulfur dioxide (SO2) emissions were detected by Infrared Atmospheric Sounding Interferometer (IASI) satellite sensors on the European Space Agency MetOp series of polar orbiting satellites on March 28 and 29. The SO2 cloud extended over interior Alaska and northwestern Canada (fig. 23) and eventually reached the southern Hudson Bay area of central Canada. The cumulative SO2 mass determined from the Ozone Mapping Profiler Suite (OMPS) satellite data obtained on 28 March was on the order of 20–30 kilotons (Simon Carn, Michigan Technological University, written commun., 2016).\r\n\"The March 28 Pavlof eruption was clearly recorded by infrasound instruments 453 km (281 mi) to the northeast at Dillingham (fig. 18). An infrasound signal was first evident at about 02:00 UTC March 28 (18:00 AKDT March 27), which corresponds to an emission time at the vent of about 01:40 UTC March 28 (17:40 AKDT March 27). The magnitude of the infrasound signals gradually rose until about 04:30 UTC March 28 (20:30 AKDT March 27) and then stabilized at high levels for several hours before declining significantly with no clear signals detected at Dillingham after about 21:00 UTC (13:00 AKDT) March 28 (David Fee, University of Alaska Fairbanks Geophysical Institute, written commun., 2016).\r\n\"By 20:40 UTC (12:40 AKDT) March 28, ash emissions were no longer evident in satellite data, and seismic activity had declined to nearly pre-eruption levels. AVO lowered the Aviation Color Code to ORANGE and the Volcano Alert Level to WATCH at 02:01 UTC (18:01 AKDT) March 29 because of the decline in robust eruptive activity.\r\n\"After March 28, 2016, unrest at Pavlof Volcano gradually declined. By April 6, 2016, ash emissions were no longer detected, and only weakly elevated surface temperatures associated with cooling deposits were observed in satellite data. At this point, AVO lowered the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY. Unrest continued to decline throughout the month of April 2016, and on April 22 AVO lowered the Aviation Color Code to GREEN and the Volcano Alert Level to NORMAL.\r\n\"Pavlof Volcano remained at background levels of unrest until May 13, 2016. At about 18:35 UTC (10:35 AKDT) May 13, seismic activity increased to levels commonly associated with low-level eruptive activity, suggesting that an eruption may have started. AVO responded by raising the Aviation Color Code to ORANGE and the Volcano Alert Level to WATCH at 20:04 UTC (12:04 AKDT) May 13. No volcanic activity was observed in satellite data or in web-camera views of the volcano on May 13. Minor ash emissions reaching as high as 6 km (20,000 ft) ASL were observed in images from the Cold Bay FAA web camera beginning around 03:46 UTC May 15 (19:46 AKDT May 14). Elevated surface temperatures were observed in satellite data on May 15, and SO2 emissions were detected in Ozone Monitoring Instrument (OMI) satellite data at 23:28 UTC (15:28 AKDT) May 17. AVO received several pilot reports of ash clouds rising to about 4.6 km (15,000 ft) ASL on May 17. This brief period of low-level eruptive activity lasted only a few days, and on May 20 AVO lowered the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY. After a few more weeks of no activity, AVO moved the Aviation Color Code to GREEN and Volcano Alert Level to NORMAL on June 17.\r\n\"The volcano remained quiet until July 1, 2016, when seismicity at the volcano began to increase, and minor steam emissions were observed in web-camera images. The increase in unrest prompted AVO to raise the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY.\r\n\"Beginning around 21:00 UTC (13:00 AKDT) July 12 web-camera images showed minor ash emissions rising just above the roughly 2.6 km (8,500 ft) high summit vent and extending a few miles to the southwest. Clear satellite views of the volcano from about this same time showed no evidence of ash emissions or elevated surface temperatures, and there was no anomalous seismicity associated with this low-level activity. After July 12, Pavlof Volcano remained in a state of low-level unrest with occasional slightly elevated surface temperatures and minor steam and diffuse ash clouds observed. The Aviation Color Code remained YELLOW and the Volcanic Alert Level ADVISORY.\r\n\"On July 28, minor eruptive activity was observed in web-camera and satellite images of Pavlof Volcano and was characterized by vigorous, steam-rich degassing and minor ash emissions. Pilots also reported seeing ash emissions as high as 2.7–3.6 km (9,000–12,000 ft) ASL. These observations coincided with a minor increase in seismicity to levels high enough to warrant raising the Aviation Color Code to ORANGE and the Volcano Alert Level to WATCH at 19:55 UTC (11:55 AKDT) on July 28. Observations of minor steam and ash emissions as high as 2.4 km (8,000 ft) ASL were made by pilots on July 31. Only weakly elevated surface temperatures were observed on August 2, and by August 4 there was no further evidence of unrest at Pavlof Volcano. Thus, AVO reduced the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY.\r\n\"Unrest at Pavlof Volcano remained slightly above background levels for about six months after early August 2016. Throughout this period, low-level steam and gas plumes from the summit and weakly elevated surface temperatures were observed occasionally when viewing conditions were favorable. The elevated surface temperatures were likely associated with still cooling pyroclastic deposits on the north flank of the volcano. By February 2017, unrest had declined to background levels although occasional, small, low-frequency events were observed in seismic data, consistent with an open, degassing system. AVO lowered the Aviation Color Code to GREEN and the Alert Level to NORMAL on February 2, 2017.\"","StartYear":2016,"StartMonth":3,"StartDay":27,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2016,"EndMonth":7,"EndDay":28,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Pavlof","ParentVolcano":"Pavlof","VolcanoID":"ak210","ParentVolcanoID":"ak210"},{"ID":4101,"Name":"Cleveland 2016/10","Description":"From Cameron and others (2020): \"The final explosion of 2016 occurred at 21:10 UTC October 25 (13:10 AKDT). This explosion was detected by the local infrasound array and seismometers and was audible as far as Nikolski, Alaska, 74 km (44 mi) northeast of the volcano. AVO raised the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH, respectively. Similar to previous explosions, most of the existing dome was removed, leaving a deep crater in its place. On November 4, the Aviation Color Code and Volcano Alert Level was lowered to YELLOW and ADVISORY, respectively, where it remained for the rest of the year despite intermittent observations of minor steaming and weakly elevated surface temperatures in the final two months of the year.\"","StartYear":2016,"StartMonth":10,"StartDay":24,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2016,"EndMonth":10,"EndDay":24,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":1301,"Name":"Bogoslof 2016/12","Description":"From Coombs and others (2019): \"Without a local seismic network, precursory seismicity was only recognized retrospectively. Wech et al. (2018) show that seismicity first occurred in September in the form of volcano-tectonic earthquakes, mostly on September 28-29 (swarm S1of Tepp et al. 2019). Wech et al. (2018) interpret these events as likely caused by magmatic intrusion into the middle to upper crust. A smaller earthquake swarm occurred in early October, with sporadic earthquakes continuing until the eruption in December (Tepp et al. 2019).\r\n\"From December 12 through March 13, explosions occurred at a mean rate of once every 58 h (2.4 days). Many of the explosions during this period were preceded by repeating earthquakes that accelerated into an explosion, characterized by increasing magnitude and becoming closer together in time, described by Wech et al. (2018) as 'slow-clap' seismicity and also described in Tepp et al. (2019) and Tepp and Haney (2019). On the basis of T-phase character, Wech et al. (2018) interpret these as occurring in the shallow crust.\r\n\"Seismicity remained at fairly low levels in October and November. In early December, days before the first detected infrasound, earthquakes with weak T-phases again suggested mid- to shallow-crustal magma movement (Wech et al. 2018). On December 12, the first infrasound signal from Bogoslof marked the beginning of the eruption. The signal, later recognized as event 1, was accompanied by a weak seismic signal, but no cloud was observed in satellite images. Infrasound for event 2, later the same day, has a relatively high frequency index (FI; ratio of high-frequency to low-frequency infrasound), suggesting a subaerial vent (Fee et al. 2019). On December 14, AVO received an email report from St. George, 308 km north-northwest of Bogoslof, about intermittent sulfur smell, likely corresponding to activity at Bogoslof. A Sentinel-2 satellite image taken minutes after event 3 on December 14 captured intense steaming from a subaerial vent and new pyroclastic deposits on the island and suspended in the surrounding ocean (Fig. 4a). Events 4 and 5 occurred on December 16 and 19. These first five explosions were not detected in real time, only after retrospective analysis of data streams. Thus, we have no direct observations of the character of these explosions.\r\n\"Satellite imagery beginning December 14 shows that uplift of Bogoslof Island occurred and may have been associated with cryptodome emplacement. A Sentinel-2 satellite image from December 21 (Waythomas et al. 2019a) shows an approximately 300-m long oval-shaped raised mass just north of Castle Rock (a remnant lava dome from the 1796-1804 eruptive period; see Fig. 3). This feature was not present in a Sentinel-2 image from December 14 (Waythomas et al. 2019a; their Fig. 5a). Preliminary analysis of DEMs generated by stereo satellite pairs shows that this feature continued to grow throughout the eruption (A. Diefenbach, written comm. 2019).\r\n\"No elevated surface temperatures were seen in satellite monitoring checks at Bogoslof until January 19, and neither the uplifted block nor surrounding areas were visibly steaming in December or January in a way that would be consistent with lava effusion (Figs. 3 and 6). Samples of the material exposed along the steep, eastward face of the uplift (see Waythomas et al. 2019b) are trachyandesite lava with 58-60 wt% SiO2 and are a different composition than the dominant juvenile basalt magma erupted in 2016-2017 (Loewen et al. 2019). Given the lack of thermal signature, as well as the composition of this feature, we suggest that this uplifted feature is likely the roof above a shallow cryptodome.\r\n\"Several pilots observed a volcanic cloud in the vicinity of Bogoslof on December 21 (Fig. 4b), and were the first alert to AVO that Bogoslof had become active. A pilot later the same day reported seeing 'a new land mass' in the island cluster. This event, event 6, began a period of activity that lasted a little less than a month, with explosive events 6-22 occurring at a rate of about one every 40 h. They produced volcanic clouds of heights up to 11 km, with variable durations (2 to 102 min), and about half produced detected lightning (Table 1). Most (80 %) consisted of single seismic pulses.\r\n\"Some of the only direct observations of activity occurred during event 9 on December 23, when observers aboard a Coast Guard vessel in the area reported ash emissions, lightning, and the ejection of incandescent lava and fragmental material that lasted about an hour. The cloud from event 16 on January 5 rose to 11.8 km asl and was observed by numerous pilots and mariners (Fig. 4c).\r\n\"A Worldview-3 image from December 25 (Fig. 6b) shows a bilobate submarine vent area and new pyroclastic deposits enlarging the island and beginning to enclose a vent lagoon. On December 29, data derived from US National Imagery Systems indicated a nearly complete ring of pyroclastic deposits around a more circular, submerged, ~ 450-m-across vent area. On January 10, passengers on a helicopter that flew from Dutch Harbor to Bogoslof took photographs and video of the island that showed discolored and roiling water in the crescent-shaped vent area, and the area of uplift from December (Fig. 3b). A Worldview-3 image from January 11 (Fig. 6c) shows continued growth of the island, and abundant meter-scale ballistics on the north and south ends of the island (Waythomas et al. 2019a, their Fig. 7).\r\n\"Satellite images, pilot reports, and ground-based photos show that event 23 on January 18 was the first demonstrably ash-rich cloud of the eruption sequence. Previous explosions produced clouds that were white in color with almost no ash signal in satellite data (Schneider et al. 2019).\r\n\"Prior to event 23, as with many other explosions on the first half of the eruption, seismic stations on neighboring islands picked up precursory seismicity in the form of repeating earthquakes that became more closely spaced in time during the runup to the explosion (Tepp et al. 2019). These lasted for about 11 h. Infrasound data show that the explosion itself lasted about 80 min and was pulsatory (Lyons et al. 2019b), with seven discrete bursts of strong seismicity (Searcy and Power 2019). Despite the event’s duration, only modest lightning was produced (14 strokes; Van Eaton et al. 2019).\r\n\"Pilots reports, visual satellite images, and thewest-facing FAA web camera in Dutch Harbor (Fig. 4d) indicated that the explosion produced a dark-gray ash cloud. MODIS satellite images show the cloud rose as high as 8.5 kmasl before drifting northeast over the Alaska Peninsula. An ash signal in the brightness-temperature-difference (BTD) satellite retrieval was seen along the leading cloud edge, suggesting that the cloud interior may have been opaque (Schneider et al. 2019). This event produced 1.9 kt of SO2 and was the first since event 13 on December 31 to produce more than 0.2 kt SO2 (Lopez et al. 2019).\r\n\"A mid-infrared MODIS satellite image collected minutes after the explosion showed a possible \"recovery pixel\". These occur when the sensor encounters a very hot object and saturates, suggesting lava or hot tephra must have been present above the water surface (D. Schneider, written comm. 2017). These were the first elevated surface temperatures detected by satellite imagery of the eruption. Clouds moved in to obscure the volcano soon after, with no additional views prior to January 20. Because event 23 was not detected on the Okmok infrasound array, we do not have infrasound FI analysis for this event, which for other events provides information on subaerial versus submarine venting (Fee et al. 2019).\r\n\"In the week following event 23, five explosions (events 24-28) occurred with an average repose time of 42 h between them (Table 1, Fig. 8). These events had total infrasound durations of 3-15 min, produced modest lightning, observable volcanic clouds, and each up to 0.6 kt of SO2 (Table 1). None showed a clear ash signature in satellite data.\r\n\"A Worldview-2 image acquired about 10 h after event 26 shows the island with a lagoon, open to the east, with two circular craters. The one to the northwest had upwelling within it, suggesting it was above the vent for the event 26 explosion (Waythomas et al. 2019a, their Fig. 8).\r\n\"About 84 h after event 28, the longest sustained explosion of the eruptive sequence produced significant ash and resulted dramatic changes to Bogoslof Island. Event 29 comprised more than 10 short-duration explosions that were detected in seismic, infrasound, and lightning data, took place over several hours on January 31, and produced several discrete volcanic clouds.\r\n\"The event started with no detected precursors, and activity escalated from 08:40 to 09:30, as indicated by increased seismic tremor and high amplitude infrasound signals. At 09:00, a continuous volcanic plume extended for a distance of more than 200 km towards the east-southeast over Unalaska Island at an altitude of 5.9 km asl. Event 29 produced 190 lightning strokes (Table 1; Van Eaton et al. 2019) and the most significant SO2 emission since December 22, 2016 (3.6 kt; Lopez et al. 2019).\r\n\"Tephra accumulation at the vent produced a demonstrably dry volcanic edifice for the first time during event 29. Data derived from US National Imagery Systems shortly after the event showed light steaming from an apparently dry eruption crater about 400 m in diameter and as much as 100 m deep below the west crater rim. Whereas most previous explosive events in the sequence, with the possible exception of event 23 on January 18, issued from a vent in shallow seawater, freshly erupted tephra formed an almost 200-m-wide barrier separating the vent from the sea. A Worldview-3 image from about 15 h later the same day (Fig. 6d) shows that the crater had already begun to fill with seawater. As with several of the events, large ballistic blocks were visible along the island’s north southwest shoreline (Waythomas et al. 2019a, their Fig. 9).\r\n\"Event 29 resulted in ashfall on Unalaska Island including trace (\u003c 0.8 mm) amounts in the community of Dutch Harbor/ Unalaska. A sample of ash collected in Dutch Harbor comprises free crystals of plagioclase, clinopyroxene, amphibole, and rare biotite, as well as particles that display a range of groundmass textures from microlitic to glassy, and that vary from dense to vesicular (Loewen et al. 2019). The material is consistent with being a mixture of juvenile basalt scoria and non-juvenile lithics.\r\n\"Following event 29, a series of smaller explosive events occurred from February 3 to 20 (events 30-36; Table 1). During this period, the inter-event times became more variable, with some pauses of up to 9 days between events. Explosions during this time lasted minutes to a few tens of minutes, produced clouds that rose from 4.6 to 8.6 km asl (Schneider et al. 2019), 0-92 strokes of lightning (Van Eaton et al. 2019), and modest SO2 (0-1.4 kt; Lopez et al. 2019).\r\n\"A series of satellite images from January 31 through February 12 shows little change in the island’s morphology after event 29 (Fig. 6d-e; Waythomas et al. 2019a). Elevated surface temperatures detected in two MODIS images from February 6 likely reflected hot new deposits from event 31 on February 4. A high-resolution Worldview-2 satellite image from February 23 also shows little change except for the presence of ballistics particles ejected during events 32-36 (February 13-20) and distributed across the island (Waythomas et al. 2019a). A clear view from March 3 similarly shows only minor changes (Fig. 6f).\r\n\"The final event in this time interval, event 36 on February 20, was an excellent example of a Bogoslof explosion with a precursory seismic sequence (see Fig. 4 of Coombs et al. 2018). A classic sequence of coalescing earthquakes served as a prelude to the series of energetic eruptive signals that made up the event. Earthquakes were first detected at 20:42 on February 19. The sequence then maintained a relatively low rate until about 00:55 (February 20) when the rate suddenly increased to about 30 earthquakes per hour. The rate then progressively increased over the next hour almost merging to tremor by 2:00. Earthquakes ceased at 2:07 and after a1-min break transitioned to tremor. The eruptive signals consisted of about 9 blasts that were captured on multiple infrasound arrays resulting in a 40-min long explosion. The resulting plume reached 6.1 km asl and was elongated, stretching to the east-southeast over Unalaska Island. Pilots and observers on Unalaska Island at the time clearly observed the white, ice-rich cloud (Fig. 4e).\r\n\"After a 16-day pause, event 37 on March 8 lasted 200 min. It had the largest infrasound energy (Lyons et al. 2019a), seismic tremor magnitude (Tepp et al. 2019), most lightning (1437 strokes; Van Eaton et al. 2019), largest SO2 emission (21.5 kt; Lopez et al. 2019), and most significant ash cloud (Schneider et al. 2019) of any event in the eruptive sequence (though not the highest reduced displacement; Haney et al. 2019a). VIIRS satellite images showed the resulting cloud reached between 10.6 and 13.4 km asl and drifted east over Unalaska Island. Minor ashfall of a few millimeters was reported by a mariner near Cape Kovrizkha (northwest Unalaska Island; Fig. 1) who collected ash from his vessel. Like the ash sample from January 31, this ash contains particles of juvenile basaltic scoria and free crystals with minor amounts of what appear to be volcanic lithics (Loewen et al. 2019). A barely perceptible ashfall deposit was reported at Unalaska/Dutch Harbor.\r\n\"Event 37 also changed the shape of the island and temporarily dried out the vent area, as seen in a Landsat-8 image from March 8 (not shown). In infrasound data, event 37 shows a mix of low and high FI, consistent with an eruption from both submarine and subaerial vent(s) during this event (Fee et al. 2019).\r\n\"A March 11 WorldView-3 image (Fig. 6g) shows the west coast of the island grew significantly since March 3 (Fig 6f), with about 250m of new land west of the 1926-1927 dome. A new ~ 150-m wide vent was also observed on the north coast of the island, and ballistics ejecta clustered on the eastern side of the island (Waythomas et al. 2019a, their Fig. 11).\r\n\"On March 10 and 11, two multi-hour seismic swarms each produced hundreds of earthquakes as detected on station MAPS (Tepp et al. 2019), but neither led directly to an explosion. A few hours later, a precursory swarm (Tepp et al. 2019) began on March 11 and culminated on March 13 in event 38. This event produced a small cloud that reached as high as 4.1 km asl and drifted south-southwest.\r\n\"Following event 38 on March 13, there was a 9-week pause in explosive activity at Bogoslof. The only detected unrest observed during the hiatus was a swarm of volcano-tectonic earthquakes on April 15. The swarm lasted for several hours, comprised 118 detected earthquakes (catalog of Wech et al. 2018) with magnitudes between ~ 0.8 and 2.2, and is interpreted to reflect magmatic intrusion in the mid to upper crust because of the earthquakes’ weak T-phases (Wech et al. 2018).\r\n\"Satellite images from this period show the rapid surface reworking and erosion of new volcanic deposits on Bogoslof Island and coastline erosion by wave action (Waythomas et al. 2019a). Photos (Fig. 5a) and a Worldview-3 image from May 11 (Fig. 6h) show that the vent lagoon remained hot throughout the hiatus, evidenced by steam rising from the crater lagoon.\r\n\"From May 16 through August 30, AVO detected 32 explosive events at the volcano. In contrast to the events of December 2016-March 2017, few of the explosions in the later phase were preceded by detectable seismic precursors, inhibiting AVO’s ability to forecast eruptive activity (Coombs et al. 2018), though retrospective analysis of hydrophone data showed that weaker precursors were still often present (Tepp et al. 2019). Fewer events produced detectable lightning after event 40 on May 28 (Van Eaton et al. 2019). This second phase also included effusion of two short-lived subaerial lava domes.\r\n\"After a nine-week hiatus, Bogoslof erupted without detectable geophysical precursors on May 17 (event 39). This explosion lasted 200 min and produced an ash cloud that reached as high as 10 km asl and drifted south along the edge of a mass ofweather clouds, as seen in GOES satellite imagery (Schneider et al. 2019) and reported by pilots. Trace ashfall (\u003c 0.8mm) was reported in Nikolski, Alaska, 123 km southwest of Bogoslof\r\n(Fig. 1). As with ash samples from the previous two events, this one contains about 40 % free crystals, though the remainder of this sample is richer in juvenile scoria (as opposed to lithic fragments) than previous ones (Loewen et al. 2019).\r\n\"Following event 39, an oblique photo showed that the crater lake was breached with a 550-m wide gap along the north shore and that the northeast shore was extended by another 300 m from new tephra deposits (Fig. 5b). Eleven days after event 39, explosive event 40 occurred on May 28, also with no detected precursors. This eruption produced an ash cloud that rose to 10.1 km asl as shown in MODIS satellite images\r\n(Schneider et al. 2019). The cloud drifted to the northeast and was reported by numerous pilots, including a report of 'sulfur' smell in cockpit from a plane about 800 km from Bogoslof. A Worldview-3 satellite image collected about 18 min after the start of the event shows the initial development of the eruption cloud (Fig. 4f; Waythomas et al. 2019a).\r\n\"These two explosive events, which occurred just after the hiatus, are among the most energetic of the eruptive sequence. They both produced appreciable SO2 clouds as detected in satellite data (9.4 and 7.7 kt; Lopez et al. 2019) and generated among the highest number of lightning  strokes (647 and 719; Van Eaton et al. 2019; Fig. 8). The remnant SO2 cloud from event 40 on May 28 was still detectable over Hudson Bay, over 4000 km east of Bogoslof, on June 2. Of the 25 events analyzed by Haney et al. (2019a), the co-eruptive tremor of these two events had the highest reduced displacement of any in the sequence-both yield values of about 50 cm2, which is comparable to values calculated for eruption tremor from the largest eruptions in Alaska over the past 20 years (e.g., Redoubt in 2009; McNutt et al. 2013).\r\n\"Cosmo SkyMed radar imagery from May 31 shows a large portion of the north side of the island was removed during May 28 explosive activity, leaving a crescent-shaped bay, open to the north. This configuration of the island remained essentially intact through June 12 (Fig. 6i).\r\n\"As seen previously from a March 8 Landsat image, sometime following May 28, intense steaming recommenced from an area just southwest of the vent lagoon. This region, about 300 m in diameter, remained hot and emitting steam throughout the eruption and afterwards (Fig. 6i-l), and may have been the site of shallow magma intrusion or a filled-in vent area.\r\n\"Early June brought a series of small explosions and growth of a lava dome that breached sea level on June 5, and was then destroyed on June 10.\r\n\"Several hours after a swarm of very small earthquakes on May 31, event 41 was a 5-min long explosion that produced a small, water-rich cloud that reached as high as 7.3 km asl. Following this, cloudy weather prevented clear views of the volcano through June 4. A Sentinel 1-B SAR image from June 4 shows no dome in the crater lagoon (Fig. 7a). Midday on June 5, data derived from US National Imagery Systems indicate that a small protrusion of lava had breached water level immediately between the 1926-1927 and 1992 lava domes in northern portion of vent lagoon. By June 6, low-resolution satellite images show distinctly elevated surface temperatures at Bogoslof, suggesting that hot lava was at the surface (Fig. 8). Sentinel-1 SAR images show the growth of the dome from June 7 through June 9 (Fig. 7b,c). On June 7, data derived from US National Imagery Systems showed that the new dome was about 110 m in diameter. The dome was also seen in a COSMO SkyMed radar image from June 8 (Waythomas et al. 2019a; their Figure 15).\r\n\"During the interval of lava effusion, several small explosive events (42-47) occurred that did not disrupt the growing dome as shown by Sentinel-1 SAR data from June 9, which confirmed that dome was still there after event 47 (Fig. 7c). Several of the events (44, 45, and 47) have infrasound frequencies consistent with a subaerial vent (Fee et al. 2019).\r\n\"The June 5 lava dome was short-lived, as it was completely destroyed during a long, pulsatory explosive event on June 10 (event 48). This event started with discrete explosions detected on the Okmok infrasound array as early as 8:27 but intensifying from 11:18 to 11:38. Starting at about 12:16, activity transitioned into nearly continuous seismic and infrasound tremor signals for about 40 min. Shorter bursts of tremor continued\r\nuntil 14:51, for an envelope of activity that lasted several hours. VIIRS satellite images of the resulting cloud showed it reached as high as 9.5 km asl and drifted to the northwest. Satellite data also indicated that at least part of the volcanic cloud was more ash-rich than many of those seen\r\npreviously in the Bogoslof eruptive sequence to date, suggesting that the eruption may have fragmented and incorporated the lava dome that was emplaced earlier that week (Schneider et al. 2019). This event generated 31 detected lightning strokes (Van Eaton et al. 2019).\r\n\"A Worldview-3 image from June 10, acquired after event 48, shows that the June 5 dome was no longer present (Waythomas et al. 2019a). Another, clearer Worldview-3 image from June 12 (Fig. 6i) showed ballistic blocks distributed uniformly around the island with the highest concentrations in the southeast and southwest sectors-likely remnants of the June 5 dome (Waythomas et al. 2019a). The FI of infrasound\r\nfrom this event gradually decreases in the last hour of the event, suggesting a change from subaerial to submarine venting after the destruction of the lava dome (Fee et al. 2019; their Fig. 8).\r\n\"On June 13, event 49 comprised a series of four explosions that started at 01:44 and ended at about 04:34. Each pulse lasted between 10 and 30 min and generated volcanic clouds that rose to a maximum height of 3.8 km asl and dissipated within about 30 min. Residents of Unalaska/Dutch Harbor reported smelling sulfur, and winds were consistent with a source at Bogoslof. An additional 2-min long explosion was detected in seismic and infrasound data later on 13 June (event 50), with no detected ash cloud.\r\n\"There was an 11-day pause in detected explosive activity from June 13-24. During an overflight on June 22, sediment-laden water was visible in the open vent lagoon area, and the area of persistent steaming was visible just east of the December uplift area (Fig. 5c).\r\n\"Twelve explosive events occurred from June 24 to July 11 (events 51-62). These were generally short-duration, detected in seismic and infrasound data, and produced little or no lightning (Table 1). Several of these events were closely spaced groups of smaller events. A photo taken on July 3 shows the area of persistent steaming visible from behind the December uplifted block, but no activity at other areas of the island (Fig. 5d).\r\n\"Following an almost month-long pause, explosive activity resumed on August 7, with a 2-h long sequence (event 63; Table 1). Detected in seismic, infrasound, satellite, and lightning data, event 63 was longer lived than many of the events in the eruptive sequence and satellite images showed that ash from the eruption formed a continuous cloud that was carried by strong winds south over Umnak Island and then out over\r\nthe Pacific Ocean reaching an altitude of 10-12 km asl (Schneider et al. 2019). Event 63 produced one of the largest SO2 masses of the eruption, 5.8 kt, as determined by IASI satellite (Lopez et al. 2019). It also yielded the highest number of lightning strokes during the second half of the eruption (117; Van Eaton et al. 2019).\r\n\"As shown in aWorldview-2 image from August 8 (Fig. 6j), event 63 produced significant proximal tephra that expanded Bogoslof Island’s northern coastline and closed off the northfacing lagoon to create a crater lake in the vent region, perhaps even leading to a subaerial vent for some portion of this explosive event. This image also shows a large number of new ballistic blocks, primarily in the east-southeast sector of the island (Waythomas et al. 2019a, their Fig. 18). In infrasound data, event 63 shows a progression from low to high FI, consistent with a shift from submarine to subaerial venting (Fee et al. 2019).\r\n\"The final 2 weeks of the eruption were marked by mostly short-duration explosions and concurrent growth of a lava dome. Events 64 through 70 were mostly short-lived (6 min or less, except event 70 which lasted 59 min; Table 1), produced little or no lightning (Van Eaton et al. 2019), and modest SO2 (up to1.2 kt; Lopez et al. 2019). Volcanic clouds from the explosions rose to high altitudes (up to 8.7 km asl; Schneider et al. 2019) despite their short durations.\r\n\"A high-resolution Worldview-3 image on August 13 shows a vent region filled with seawater and no lava dome was apparent (Fig. 6k). On August 15, repeating low-frequency seismic events from Bogoslof were detected on Okmok and Makushin networks for about 8 h (Tepp et al. 2019). A photo from an overflight of the volcano on August 15 shows the area of persistent steaming visible since late May, but nothing at the site of the dome that would appear days later in the vent lagoon (Fig. 5e). If the August 15 seismicity was related to magma ascent, it had not yet risen shallowly enough to impact the vent lagoon area.\r\n\"A new lava dome was observed in data derived from US National Imagery Systems in the enclosed, water-filled crater on August 18 and grew to about 160 m in diameter and 20 m tall by August 22. A Sentinel SAR view shows the dome on August 20 (Fig. 7d). An oblique aerial photo taken on August 26 shows a vigorous steam plume that likely was generated as hot dome rock interacted with seawater in the vent lagoon area (Fig. 5f).\r\n\"SAR images from Sentinel-1 (Fig. 7e) and Cosmos SkyMed (Fig. 7f) on August 27, after event 66, suggest that most of this dome had been removed, with only some northern dome edge remnants remaining. The low-frequency infrasound associated with events 66-69 suggest that the vent was below water (Fee et al. 2019).\r\n\"Following the last explosive activity on August 30, there were a few earthquakes detected in seismic and hydrophone data (G. Tepp, written comm. 2019), but seismic activity quieted soon after. In August 2018, AVO added a telemetered seismometer on Bogoslof Island, which has recorded little activity of note.\r\n\"Weakly elevated surface temperatures were consistently observed at Bogoslof in low-resolution satellite images through November 2017. High-resolution satellite images from the fall of 2017 show steaming and discoloration on the island (e.g., Fig. 6l). As of 2019, continued erosion has changed the shape of the island (Waythomas et al. 2019b), similar to what occurred following previous eruptions.\"","StartYear":2016,"StartMonth":12,"StartDay":12,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2017,"EndMonth":8,"EndDay":30,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Bogoslof","ParentVolcano":"Bogoslof","VolcanoID":"ak29","ParentVolcanoID":"ak29"},{"ID":4111,"Name":"Cleveland 2017/2","Description":"From Dixon and others, 2020: \"Mount Cleveland began the seventh straight year at an elevated Aviation Color Code and Volcano Alert Level in 2017. Activity consisted of intermittent elevated surface temperatures, degassing from the summit cone, and the extrusion of small lava domes punctuated by explosions. Mount Cleveland began 2017 with fewer but similarly sized explosions to those in previous years that transitioned into more frequent but smaller explosions towards the end of the year...\r\n\"Mount Cleveland began 2017 at Aviation Color Code YELLOW and Volcano Alert Level ADVISORY. The last explosion on October 24, 2016, left a deep crater at the start of 2017. Activity in January consisted of intermittent gas plumes and elevated surface temperatures. By January 21, satellite imagery confirmed that a new lava dome partially occupied the summit crater. The dome measured 30 m (100 ft) in diameter on January 24, and by February 3 it was 70 m (230 ft) in diameter. The extrusion of this lava dome and potential for explosive activity prompted AVO to increase the Aviation Color Code to ORANGE and the Volcano Alert Level to WATCH on February 3. The dome ceased growing at 75 m (250 ft) in diameter around February 11 and remained unchanged into March, and weakly elevated surface temperatures and minor gas emissions were detected in satellite imagery and web-cameras during this time, consistent with cooling lava. After several weeks of inactivity, the Aviation Color Code and Volcano Alert Level was downgraded from ORANGE and WATCH to YELLOW and ADVISORY, respectively, on March 8. \r\n\"The first explosion of 2017, which occurred on March 24 at 16:15 UTC (08:15 AKDT), removed the lava dome. The short-duration explosion showed characteristics similar to previous dome-related explosions with a very sharp onset followed by about 10 seconds of additional signal in infrasound data. Cloud cover prevented the observation of ash cloud from this event. This explosion prompted the Aviation Color Code and Volcano Alert Level to be upgraded from YELLOW and ADVISORY to ORANGE and WATCH, respectively. \r\n\"On April 5, the Aviation Color Code and Volcano Alert Level was downgraded from ORANGE and WATCH to YELLOW and ADVISORY, respectively, because of inactivity since the explosion on March 24. Satellite imagery showed a new lava dome was extruded into the summit crater sometime before April 15 and by April 23 grew into a smooth 45-m- (150-ft-) diameter dome. The presence of a growing lava dome in the summit crater of Mount Cleveland prompted an Aviation Color Code and Volcano Alert Level upgrade to ORANGE and WATCH, respectively, on April 24. Extrusion of lava continued, and by April 28 three stacked domes had formed. The lowermost dome was 60 × 50 m (200 × 160 ft), the second dome 40 × 30 m (130 × 100 ft), and the newest and topmost dome was 15 m (50 ft) in diameter. The topmost circular dome continued to grow, and by May 2, it was greater than 20 m (65 ft) in diameter. Satellite imagery from May 8 showed no change in the size of the top dome, signifying that lava effusion had ceased at Mount Cleveland. \r\n\"On May 17, 03:17 UTC (May 16, 19:17 AKDT), an automated infrasound alarm indicated an explosion. A continuous broadband signal was recorded clearly in seismograph data and was also seen in infrasound data at stations CLES and CLCO for 10 minutes after the initial explosion. The extended infrasound signals were likely caused by jetting (continuous, vigorous gas emissions) after the destruction of the lava dome in the vent. The resulting ash plume drifted approximately 140 km (87 mi) to the southwest at an altitude of 4.6 km (15,000 ft) and was observed in visible Geostationary Operational Environmental Satellite imagery until nightfall. Satellite imagery just after the explosion showed that the dome was completely removed, and impact craters from ballistic dome fragments were formed on the upper flanks of the volcano. The Mount Cleveland summit crater was dome free through May 26. \r\n\"On June 6, a series of repeating small low-frequency seismic events were recorded on seismograph station CLES, 3.5 km (2.1 mi) from the summit, but these events were not seen on nearby seismograph station CLCO, 15 km (9 mi) from the summit. The seismicity was consistent with lava dome growth, but poor viewing conditions prevented the confirmation of dome growth. On June 26, the Aviation Color Code and Volcano Alert Level was reduced from ORANGE and WATCH to YELLOW and ADVISORY, respectively, owing to the decline in activity. \r\n\"On July 4, 11:19 UTC (03:19 AKDT), a moderate 10-minute eruption was detected by both seismograph and infrasound sensors, prompting the Aviation Color Code and Volcano Alert Level to be upgraded from YELLOW and ADVISORY to ORANGE and WATCH, respectively. This explosion differed from the previous explosion by being preceded by at least five low-frequency seismic events. Additionally, a burst of tremor was recorded 15 seconds prior to the onset of the main explosion.\r\nSatellite data from July 17 show that a new 25-m- (80-ft-) diameter lava dome was emplaced in the summit crater. It grew to more than 50 m (160 ft) in diameter with increased vertical inflation by August 1. Satellite imagery on August 7 showed no change in the lava dome from the previous satellite images, signifying that lava effusion had ceased. This small lava dome was observed by an AVO field crew during an overflight of Mount Cleveland on August 17.\r\n\"The fourth explosion in 2017 occurred on August 22 at 18:43 UTC (10:43 AKDT). The one-minute explosion had no precursory activity and was detected by both seismograph and infrasound sensors. Satellite imagery suggested that this explosion, like the previous three eruptions, removed the existing lava dome. The crater remained empty for more than a month until another explosion occurred on September 26, 01:47 UTC (September 25, 17:47 AKDT). The initial blast lasted 3 seconds, but after a brief 15-second pause, a roughly 2-minute-long broadband signal was detected in both seismic and infrasound data suggesting an initial vulcanian blast that was followed by continuous emissions. An ash cloud was visible in a NOAA-19 satellite image south of Mount Cleveland for 30 minutes after the explosion.\r\n\"The explosions later in 2017 were smaller and more frequent than those at the beginning of the year. Two small explosions occurred on September 28 at 13:19 and 13:58 UTC (05:19 and 05:58 AKDT, respectively) with amplitudes approximately 100 times smaller than the explosion 2 days prior. Another small explosion occurred on October 1, at 13:05 UTC (05:05 AKDT). \r\nSatellite observations on October 1 showed a new lava dome greater than 70 m (230 ft) in diameter, and by October 15, the dome had doubled in area to cover 12,500 square meters (m2;134,500 square feet [ft2]) at a height of 15-20 m (50-65 ft). The dome continued to increase in both area and height through October 23. On October 28, a small, short-duration (30 sec) explosion occurred at 18:45 UTC (10:45 AKDT). A smaller explosion occurred on October 30 at 11:20 UTC (03:20 AKDT). Satellite imagery suggests that the October explosions removed a portion of the central vent from the dome. A small explosion occurred on November 12 at 09:56 UTC (00:56 AKST) followed by a similar-sized explosion on November 14 at 12:15 UTC (03:15 AKST). The latter event was preceded by two local earthquakes 1 hour prior to the explosion. Another small explosion occurred on November 16 at 22:44 UTC (13:44 AKST) that was similar to the previous events. Between November 17, 22:00 UTC (13:00 AKST) and November 18, 08:20 UTC (November 17, 23:20 AKST), a small volcanic-tectonic earthquake swarm occurred in the vicinity of Mount Cleveland, but its significance to the Mount Cleveland eruption sequence has yet to be determined. A small explosion occurred on December 4, 07:21 UTC (December 3, 22:21 AKST) that was seen just at the closest seismograph station to the summit (CLES).\r\n\"Decreased activity following the December 4, 2017, explosion was interpreted as cessation of lava effusion at Mount Cleveland, which prompted AVO to change the Aviation Color Code and Volcano Alert Level from ORANGE and WATCH to YELLOW and ADVISORY, respectively, on December 12. However, less than a day later, another explosion occurred on December 13 at 13:20 UTC (04:20 AKST) necessitating that the Aviation Color Code and Volcano Alert Level to be returned to ORANGE and WATCH, respectively. The ash cloud from this eruptive event was visible in satellite imagery and drifted east at an altitude of 6.1 km (20,000 ft). The final explosion of 2017 occurred on December 18 at 03:17 UTC (December 17, 18:17 AKST), and like recent explosions was smaller than the explosions in early 2017. The Aviation Color Code and Volcano Alert Level remained at ORANGE and WATCH, respectively, for the remainder of the year.\"\r\nFrom Cameron and others, 2023: \"In addition to the preexisting volcanic activity alarms at Mount Cleveland, AVO implemented two new alarms in 2018 to help detect sudden explosions. One alarm uses the co-located seismic and infrasound sensors at station CLES to quickly detect smaller explosions, and the other uses seismic data in the very-long-period band from station CLCO. This second alarm became especially useful after CLES had an extended data outage starting in September 2018; for the latter part of the year, AVO had only CLCO to supplement the usual remote sensing techniques used to monitor Mount Cleveland. \r\n\"Mount Cleveland began 2018 at Aviation Color Code ORANGE and Volcano Alert Level WATCH, a response to its previous explosion on December 18, 2017, at 03:17 UTC (December 17 at 17:17 HAST). After several months without explosive activity, on February 9, 2018, AVO downgraded the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY. The first explosion of 2018 took place on March 2 at 14:57 UTC (04:57 HAST) and was detected by AVO’s automated infrasound alarms. The acoustic amplitude of the explosion was similar to that of the previous explosion, and ground-coupled airwaves were detected as far as the Pavlof Volcano and Korovin Volcano seismic networks (747 km [464 mi] and 1,025 km [637 mi] away, respectively). A small volcanic cloud was observed in satellite data moving east-northeast shortly after the explosion. The event prompted AVO to raise the Aviation Color Code and Volcano Alert Level again to ORANGE and WATCH. After a few days with no substantial eruptive activity, on March 5, AVO downgraded the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY. \r\n\"The next explosion took place on March 15 at 06:19 UTC (March 14 at 21:19 HADT) and was detected by the Mount Okmok infrasound array. The ground-coupled airwaves from this event were also detected by the Mount Okmok seismic network. Mount Cleveland produced another short-lived explosion on April 4 at 11:55 UTC (02:55 HADT), and possible jetting took place about 40 minutes later. In contrast to other explosions on Mount Cleveland, which typically have no notable precursory activity, a low-frequency seismic event preceded the April 4 explosion by about 19 hours. Satellite imagery taken after the explosion indicated the presence of hot material on the west flank from the summit down to the coast and a small volcanic cloud drifting at an altitude of about 19,000 ft (5,800 m) ASL. AVO upgraded the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH in response to this explosion. Activity on the volcano declined after April 4, and on April 6, AVO downgraded the Aviation Color Code and Volcano Alert Level back to YELLOW and ADVISORY. Another small explosion took place on April 13 at 15:59 UTC (06:59 HADT). \r\n\"The next explosion at Mount Cleveland took place on May 5 at 06:08 UTC (May 4 at 21:08 HADT) and was detected by both the newly implemented seismic and acoustic alarms at CLES and by the previously running alarms on the CLCO infrasound array. A small volcanic cloud from the explosion, visible in satellite imagery, drifted southeast at an altitude of about 22,000 ft (6,700 m) ASL. In response to the event, AVO raised the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH. After no new explosive activity, on May 6, AVO downgraded the Aviation Color Code and Volcano Alert Level back to YELLOW and ADVISORY. The event on May 5 was the last in Mount Cleveland’s first cluster of explosions in 2018. \r\n\"On June 3 and 9, two small swarms of local earthquakes took place near Mount Cleveland but did not appear to be associated with any explosive activity... Satellite imagery indicated that between June 19 and 25, a new lava dome measuring 80 m [260 ft] in diameter grew within the crater. The appearance of the dome prompted AVO to upgrade the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH because the presence of lava over the active vent increased the possibility of a vent-clearing explosion. After a few months without explosive activity, on August 22, AVO downgraded the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY. \r\n\"A data outage took place at the local monitoring station (CLES) on September 23 and persisted for the rest of the year, leaving the seismometer at the distal station (CLCO) as the only local instrumentation to supplement AVO’s remote sensing techniques. \r\n\"The second cluster of explosions to affect Mount Cleveland in 2018 began on December 10 at 08:55 UTC (December 9 at 22:55 HAST). The seismic amplitude of this first explosion, which was similar to that of previous explosions in 2018, triggered the seismic alarm at station CLCO. The seismic stations in the town of Nikolski, Alaska, and at Mount Okmok recorded ground-coupled airwaves. Satellite imagery taken after the explosion indicated that most of the summit lava dome was removed and that new debris flow deposits extended 2.6 km [1.6 mi] east-northeast of the summit. Another explosion took place on December 12 at 20:52 UTC (10:52 HAST), with an amplitude about 1.5 times larger than the previous explosion. The same day, AVO upgraded the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH. \r\n\"The next explosion in the cluster took place on December 16 at 16:37 UTC (06:37 HAST). It triggered the seismic alarm and was also detected by the Mount Okmok seismic network in the form of weak, ground-coupled airwaves. This explosion was slightly larger than the previous one, producing a small ash cloud that reached an altitude of about 25,000-30,000 ft (7,600-9,100 m) ASL, possible SO2 gas emissions, and a single stroke of lightning (detected by the World Wide Lightning Location Network). Mount Cleveland produces volcanic lighting infrequently; its only other known occurrences took place in 2009 and 2014. The final explosion of Mount Cleveland in 2018 took place on December 29 at 03:17 UTC (December 28 at 17:17 HAST). A pilot weather report from after the explosion described an ash cloud reaching an altitude as high as 17,000 ft (5,200 m) ASL. Mount Cleveland remained at Aviation Color Code and Volcano Alert Level ORANGE and WATCH for the remainder of 2018.\" \r\nFrom Orr and others, 2023: \"Mount Cleveland was relatively quiet during 2019, producing only one small explosive eruption in early January. Despite the paucity of eruptions, its behavior otherwise was similar to that of previous years, with elevated surface temperatures and nearly continuous degassing from the summit that produced weak steam emissions. \r\n\"The volcano began 2019 at an Aviation Color Code and Volcano Alert Level of ORANGE and WATCH, having erupted a few days earlier on December 29, 2018. On January 7, 2019, after several days of quiescence, AVO downgraded the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY. The volcano answered with a small explosion on January 9, recorded in local seismic and infrasound data. No associated plume was observed above the meteorological clouds, which reached an altitude of about 10,000 ft (3,000 m) ASL at the time. Later satellite imagery showed a thin tephra deposit extending southeast from the summit. AVO did not change the Aviation Color Code and Volcano Alert Level in reaction to this event. \r\n\"Satellite imagery taken on January 12 revealed the presence of a new dome 75 m [250 ft] in diameter, and by January 17, it had grown to 90 m [300 ft]. In response, AVO raised the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH. The dome stopped growing soon after, and when no explosion took place, the Aviation Color Code and Volcano Alert Level were lowered back to YELLOW and ADVISORY on February 25.\"","StartYear":2017,"StartMonth":2,"StartDay":3,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":2,"EndDay":25,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":4121,"Name":"Pavlof 2017/6","Description":"The Aviation Color Code for Pavlof Volcano was raised to YELLOW on Wednesday, June 7 following an increase in low-frequency seismic activity and a pilot report indicating a possible ash cloud to 4000 ft asl. Active degassing from the summit was observed in web camera images and by local observers in Cold Bay yesterday and this morning. Infrasound data from local instruments on Pavlof and a more distant network in Sand Point show no evidence of significant explosive activity during the past week. Seismic activity has been at background levels since Thursday, June 8. Precursory activity leading up to previous explosive eruptions at Pavlof have been subtle and while some episodes of increased seismic activity have preceded eruptive episodes other increases have died back down without explosive activity.\r\n\r\nWeakly elevated surface temperatures and vapor plumes continued to be observed at Pavlof, but declined through June, July, and August. On August 30, 2017, citing normal, background levels of activity at Pavlof, AVO lowered the Aviation Color Code and Volcano Alert Level to GREEN/NORMAL.","StartYear":2017,"StartMonth":6,"StartDay":7,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2017,"EndMonth":8,"EndDay":30,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Pavlof","ParentVolcano":"Pavlof","VolcanoID":"ak210","ParentVolcanoID":"ak210"},{"ID":4131,"Name":"Great Sitkin 2016/7","Description":"From the AVO Volcano Activity Notice of November 22, 2017: Recent observations of a robust steam plume and a period of gradually increasing seismicity over several months indicate that Great Sitkin Volcano has become restless and is exhibiting behavior that is above background levels. AVO is thus raising the aviation color code and volcano alert level to YELLOW/ADVISORY.\r\n\r\nPhotographs of the volcano taken by local observers on Sunday, November 19 show a light-colored vapor plume rising about 300 m (1,000 ft) above the vent area and extending about 15-20 km (9 -12 mi) to the south. Nothing unusual was observed in seismic or infrasound data around the time the photographs were taken and nothing noteworthy has been observed in satellite data since the emissions were observed. \r\n\r\nAn increased number of small earthquakes was evident as early as late July 2016, and since then the level of seismic activity has fluctuated at low levels but has exhibited a gradual overall increase most notable since June 2017. Seismic activity to date has been characterized by earthquakes that are typically less than magnitude 1.0 and range in depth from near the summit of the volcano to 30 km below sea level. Most earthquakes are in one of two clusters, beneath the volcano's summit or just offshore the northwest coast of the island. The largest earthquake so far was a magnitude 2.8 on September 29, 2017.\r\n\r\nPossible explosion signals were observed in seismic data on January 10 and July 21 of [2017] but no confirmed emissions were observed locally or detected in infrasound data or satellite imagery.\r\nAfter two months of declining seismicity, AVO lowered Great Sitkin to Green/Normal on January 18, 2018.","StartYear":2017,"StartMonth":6,"StartDay":30,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2017,"EndMonth":12,"EndDay":null,"EndTime":null,"EndQualifier":1,"EndQualifierUnit":"Months","Volcano":"Great Sitkin","ParentVolcano":"Great Sitkin","VolcanoID":"ak111","ParentVolcanoID":"ak111"},{"ID":4844,"Name":"Shrub 2017/10","Description":"From Cameron and others, 2023: \"In the fall of 2017, a new eruption began low on the southeast flank of Shrub mud volcano, discharging a mud flow that wrapped around the south side of the base of the cone. This was the first new activity observed at Shrub mud volcano since the late 1990s and marked its first flank eruption since 1996, when a pilot reported seeing mud erupting from a vent low on the north flank of the volcano. Satellite imagery indicates that the 2017 activity began sometime between October 16 and October 20 and continued for several months, but given the poor quality of available imagery, it is equally likely that the event comprised two or more eruption episodes separated by pauses. A comparison between the mud flow extent visible in high-quality satellite imagery from June 2018 and helicopter overflight photos taken in June 2019 indicates that the eruption continued after June 2018.\"","StartYear":2017,"StartMonth":10,"StartDay":null,"StartTime":null,"StartQualifier":2,"StartQualifierUnit":"Days","EndYear":2018,"EndMonth":12,"EndDay":null,"EndTime":null,"EndQualifier":6,"EndQualifierUnit":"Months","Volcano":"Shrub","ParentVolcano":"Klawasi Group","VolcanoID":"ak253","ParentVolcanoID":"ak163"},{"ID":4331,"Name":"Shishaldin 2017/12","Description":"From Dixon and others, 2020: \"Shishaldin Volcano did not erupt in 2017, but volcanic unrest in December resulted in an elevated Aviation Color Code and Volcano Alert Level of YELLOW and ADVISORY, respectively, for much of the month. On April 20, AVO received a pilot report of an ash rich plume. Web-camera images confirmed the plume was composed of gas with no evidence of ash. Gas plumes are common at Shishaldin Volcano, and occasional reports of gas plumes and increased low-frequency seismic events were reported in AVO’s internal logs for most of 2017. \r\n\"In the last week of October, AVO noted elevated surface temperatures at the summit of Shishaldin Volcano. Throughout November, AVO observed increased low-frequency seismicity likely to be associated with small explosions. At the end of November, these explosions were being recorded on the infrasound array at Sand Point, Alaska, 230 km (140 mi) east of the volcano. In response to multiple signs of unrest, AVO elevated the Aviation Color Code to YELLOW and Volcano Alert Level to ADVISORY on December 6. Observations of degassing and energetic small explosions continued through December.\"\r\nFrom Cameron and others, 2023: \"The overall activity at Shishaldin Volcano declined throughout January 2018, and on February 7, 2018, this continued decline triggered AVO to lower the Aviation Color Code and Volcano Alert Level of the volcano to GREEN and NORMAL. No other notable unrest took place at the volcano for the remainder of 2018.\"","StartYear":2017,"StartMonth":11,"StartDay":null,"StartTime":null,"StartQualifier":14,"StartQualifierUnit":"Days","EndYear":2018,"EndMonth":1,"EndDay":null,"EndTime":null,"EndQualifier":30,"EndQualifierUnit":"Days","Volcano":"Shishaldin","ParentVolcano":"Shishaldin","VolcanoID":"ak252","ParentVolcanoID":"ak252"},{"ID":4321,"Name":"Novarupta 2017/11","Description":"From Dixon and others (2020): \"On June 4, 2017, a National Oceanic and Atmospheric Administration (NOAA) and National Environmental Satellite, Data, and Information Service ash alert reported a possible resuspension event over the Valley of Ten Thousand Smokes (fig. 9). Atypical, easterly winds carried resuspended ash away from population centers so that an AVO Information Statement was not issued. AVO alerted the NWS Alaska Aviation Weather Unit * * * , \r\n\"Two ash resuspension events were detected in November, and the first was identified by a NOAA and Cooperative Institute for Meteorological Satellite Studies ash alert. On November 10, strong northwest winds over the Valley of Ten Thousand Smokes resuspended volcanic ash into a visible cloud and transported it eastward across Shelikof Strait and over Kodiak Island, where it was detected by the AVO particulate monitors at Larson Bay on the west coast of Kodiak Island. A similar sensor in the city of Kodiak, Alaska, on the east coast of Kodiak Island did not record any ash for this episode. AVO issued an Information Statement corroborating the hazard notifications issued by the NWS. By the evening of November 10, the resuspension event started to wane despite the surface winds continuing with gusts up to 20 meters per second (66 feet per second). A similar resuspension event occurred on November 13. The resuspended ash cloud extended 120 km (72 mi) to the southeast over the south end of Kodiak Island where no particulate monitors were installed. (fig. 10). AVO issued another Information Statement after the detection of this resuspension event.\"","StartYear":2017,"StartMonth":11,"StartDay":10,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2017,"EndMonth":11,"EndDay":13,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Novarupta","ParentVolcano":"Novarupta","VolcanoID":"ak203","ParentVolcanoID":"ak203"},{"ID":4847,"Name":"Pavlof non-eruptive activity 2018","Description":"From Cameron and others, 2023: \"The number of located earthquakes at Pavlof Volcano increased in 2018 compared to previous years. Although this increase was at least in part due to improvements to the local seismic network, there are indications that seismic activity in 2018 was nonetheless above background levels. Shallow LP earthquakes are common at the volcano, and the relative amplitudes of their waveforms, as observed by the Pavlof Volcano seismic network, indicate they tend to be located at or near the volcano summit. Although these events are commonly too small to be located by AVO’s routine earthquake location procedures, they are observable on spectrograms and are still noted in AVO’s routine seismic checks (Power and others, 2020). Similar activity has been observed at other open-vent systems in the Aleutian Arc, such as Shishaldin Volcano (Petersen and others, 2006; Pesicek and others 2018) and Mount Veniaminof (Pesicek and others, 2018), and appears to be typical for such systems (Quezada-Reyes and others, 2013). \r\n\"The Pavlof Volcano seismic network [in 2018] consists of three broadband digital seismic stations (PN7A, PS1A, and PS4A), three short-period 3-component stations (PV6A, PVV, and HAG), and one short-period vertical-component station (BLHA). The current configuration is fairly new; AVO carried out substantial upgrades to the network in the summer of 2017, during which PN7A, PS1A, PVV, and PS4A were upgraded to broadband digital stations, PV6 was replaced by PV6A, and HAG was upgraded from a vertical-component analog station to a 3-component station (Dixon and others, 2019). \r\n\"AVO located 152 earthquakes within a 20-kilometer radius of Pavlof Volcano in 2018...Throughout 2018, the volcano remained at Aviation Color Code GREEN and Volcano Alert Level NORMAL. Of the events that occurred in 2018, 111 were designated as LP earthquakes and 41 as volcano-tectonic (VT) earthquakes...Moderately deep LP earthquakes (10-20 km [6-12 mi] deep) took place in a broad swath east of Pavlof Volcano and Pavlof Sister throughout 2018, and although these events appear to be well-located based on reported root mean square errors (0.05-0.33), they often had small magnitudes. \r\n\"On March 27, 2018, an unusual cluster of VT earthquakes took place about 6-8 km [3.7-5 mi] north-northwest of Pavlof Sister and 12-13 km [7.5-8 mi] north of Pavlof Volcano. The earthquakes were 6.6-9.0 km [4.1-5.6 mi] below sea level with local magnitudes (ML) between 0.3 and 1.5. Later, in early April, a sequence of deep LP earthquakes took place near Pavlof Sister. These events were 10.1-29.3 km [6.3-18.2 mi] below sea level with ML values between −0.37 and 1.99, but only two events from the sequence were above ML 1.0. On September 11, another series of deep LP earthquakes took place in the same location as the March LP earthquake activity. The September 11 sequence had nine events, the two largest being ML 1.3 and 1.4. The hypocentral depths of these nine events ranged from 26 to 32 km [16-20 mi]. The sequence was also accompanied by a short tremor episode lasting about four minutes, though the tremor may have actually been closely spaced LP earthquakes. \r\n\"Volcano-tectonic earthquakes are not as common at Pavlof Volcano as at other volcanic systems, making the March 2018 brittle failure sequence notable. These events are assumed to have been distal VT earthquakes on the basis of their location (12-13 km [7.5-8 mi] from Pavlof Volcano), though they also may have been tectonically generated. AVO has not located any similar cluster in the same area since it began monitoring the volcano in 1996. The fact that there were more located events in 2018 than in previous years is not surprising given the network improvements made in 2017. Many of the 2018 events were of small magnitudes, and the increase in earthquake locations is partly due to the improved network. However, the additional presence of the March VT earthquake cluster and the LP earthquakes above ML 1.0 indicate the 2018 activity may have been above background levels for the upgraded network, suggesting increased magmatic activity at Pavlof Volcano in 2018. Alternatively, this behavior may be typical for the volcano but is only observed now because of the improved network. \r\n\"Observations made by Power and others (2004) of deep LP earthquake activity throughout the Aleutian Arc suggest a link between magma movement in the lower to middle crust and eruptive activity, although the timing between these parameters appears to vary. The deep LP earthquake activity at Pavlof Volcano may indicate the presence of continued magma supply to the volcano, with 2018 a slightly more active year. Further monitoring of earthquake activity at Pavlof Volcano will likely shed light on the magmatic system that feeds eruptive activity at the volcano.\"","StartYear":2018,"StartMonth":1,"StartDay":1,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2018,"EndMonth":12,"EndDay":31,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Pavlof","ParentVolcano":"Pavlof","VolcanoID":"ak210","ParentVolcanoID":"ak210"},{"ID":4850,"Name":"Makushin unrest 2018","Description":"From Cameron and others, 2023: \"Makushin Volcano continued showing signs of unrest in 2018. After the eruption of nearby Bogoslof volcano in 2016-2017, reports of steaming from the summit of Makushin Volcano increased in frequency. The number of located earthquakes near Makushin Volcano has also increased since 2012. Despite these mild signs of unrest, no observations were enough to raise the Aviation Color Code or Volcano Alert Level, which remained at GREEN and NORMAL throughout the year.\r\n\"Steam emissions from Makushin Volcano were noted multiple times in the summer of 2018, both through webcam images seen by observatory personnel and in reports sent to AVO by residents of the City of Unalaska, Alaska. None of these reports differ in content from previous reports archived at AVO, which go back more than a decade. The increase in reports may be due in part to the activity at Bogoslof volcano, which could have prompted residents to forward more observations to AVO. \r\n\"Independent of the increased frequency of reports of steaming, AVO performed its first aerial summit gas survey at Makushin Volcano in the summer of 2018. Gas observations from the volcano’s gas plume yielded SO2 fluxes of ~100 t/d along with low CO2/Stotal (~1.5/2.5) and SO2/H2 S ratios (~1.1/1.7). These observations are consistent with degassing from a hot, mixed magmatic-hydrothermal system. The presence of SO2, a magmatic gas, has not previously been detected from ground-based measurements at Makushin Volcano, although it was also detected at the volcano by a new instrument, the TROPOspheric Monitoring Instrument on the Copernicus Sentinel-5 Precursor satellite, which launched in the fall of 2017. Until repeat surveys establish baseline data, however, the significance of this SO2 is unknown. \r\n\"The increase in seismicity that began in 2012 continued in 2018, with more than 1,000 earthquakes located by AVO near Makushin Volcano during the year. As is typical for Makushin Volcano seismicity, several short earthquake swarms were noted. Four of these clusters, which took place in the months of January, July, September, and November, were located 5-10 km [3.1-6.2 mi] southeast of the summit, making this area the most seismically active on the volcano. Three more swarms took place in January, March, and June, about 20 km [12.5 mi] to the northeast, southwest, and southeast of the summit, respectively.\"","StartYear":2018,"StartMonth":1,"StartDay":1,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2018,"EndMonth":12,"EndDay":31,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Makushin","ParentVolcano":"Makushin","VolcanoID":"ak188","ParentVolcanoID":"ak188"},{"ID":4852,"Name":"Gareloi 2018/06","Description":"From Cameron and others, 2023: \"The typical seismicity of Mount Gareloi is characterized by many low-frequency earthquakes that are commonly too small to be located by its seismic network, which comprises six stations on Gareloi Island and nearby Kavalga Island. Although the frequency of located seismic events varied in the past, seismicity at Mount Gareloi was fairly constant in recent years: 265 earthquakes were located in 2016 and 269 were located in 2017. In the summer of 2018, however, AVO located an anomalously high number of earthquakes, with 190 located in June and 178 in July. AVO then located 80 earthquakes in August and 77 in September before the volcano returned to typical activity levels in the fall. This period of increased activity was dominated by low-frequency earthquakes at depths of 5–15 km, which is typical for seismicity at Mount Gareloi. AVO paid close attention to the elevated seismicity rates but kept the Aviation Color Code and Volcano Alert Level at GREEN and NORMAL. \r\n\"In 2022, while retrospectively reviewing high-resolution satellite imagery of Mount Gareloi, AVO found a 2018 image showing an approximately 5-kilometer-long ash deposit extending north-northwest from the south fumarole field of the volcano. This image, taken by the WorldView-2 satellite on June 12, appears to record a previously unrecognized small ash emission (eruption). Satellite imagery acquired by Planet Labs PBC first shows the ash streak on June 6; the actual emission may have taken place on June 5.\"","StartYear":2018,"StartMonth":6,"StartDay":1,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2018,"EndMonth":9,"EndDay":30,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Gareloi","ParentVolcano":"Gareloi","VolcanoID":"ak106","ParentVolcanoID":"ak106"},{"ID":4845,"Name":"Spurr non-eruptive activity 2018","Description":"From Cameron and others, 2018: \"From June 6 to 9, 2018, AVO noted a sequence of seismic events on seismograph station STLK, located about 31 km [20 miles] east of Mount Spurr near Strandline Lake. This sequence was interpreted as glacial movement in the Strandline Lake area, but its precise source could not be located because only one station recorded the seismicity. The activity began on June 6 at 17:07 UTC (09:07 AKDT) with a series of weak, low-frequency earthquakes that increased in rate for an hour, at which point a 9-minute tremor-like signal was recorded (fig. 2). Earthquakes resumed after the tremor, and although they took place at a lower event rate, they also produced the highest amplitudes of the sequence. Earthquakes decreased in amplitude considerably over the next 9 hours, but weak earthquakes continued until 15:35 UTC (07:35 AKDT) on June 9. About 950 earthquakes were detected in the entire sequence, with 90 taking place prior to the tremor. This sequence was similar to previously described seismicity produced by weather-related glacial movements (for example, Thelen and others, 2013; Allstadt and Malone, 2014), and the earthquakes likely reflected stick-slip movement of the glacier, with the tremor burst produced by a period of continuous motion. Changes in the character of the earthquakes, including increasing durations, through the sequence indicate the seismicity source was changing over time - either in location or source conditions.\"","StartYear":2018,"StartMonth":6,"StartDay":6,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2018,"EndMonth":6,"EndDay":9,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Spurr","ParentVolcano":"Spurr","VolcanoID":"ak260","ParentVolcanoID":"ak260"},{"ID":4341,"Name":"Great Sitkin phreatic 2018","Description":"From Cameron and others, 2023: \"During 2018, AVO located more than 2,300 earthquakes at Great Sitkin Volcano, principally clustered in the shallow crust (extending from the summit to roughly 10 km [6.2 mi] below sea level). Additional earthquakes were also located between 15 and 35 km [9 and 22 mi] depth, with waveforms and frequency contents suggesting both VT and deep LP earthquakes. The magnitudes of these located events ranged from an ML of less than −1.0 to 2.48 - the largest event took place on August 31, 2018. Unfortunately, the Great Sitkin Volcano seismic network experienced several station failures in 2018, most importantly at stations GSTD and GSSP, which impaired AVO’s ability to locate earthquakes and resulted in the data gaps. The most notable of these failure periods spanned early November 2017 to mid-January 2018. Shorter-term failures of station GSSP also compromised AVO’s earthquake locating capabilities during the winter of 2018-2019. AVO identified several tremor bursts associated with this unrest during 2018, with most taking place between June and December. Interpreted as small explosion events, the tremor bursts contained a variety of waveforms with impulsive to emergent onsets, extended codas, and frequency between 1 and 15 hertz. The bursts were commonly associated with increased earthquake activity, but none produced infrasound signals identifiable by sensors in the nearby City of Adak, Alaska. The explosion of June 10, 2018, proved especially noteworthy when a Sentinel-2 satellite image acquired on June 11 at 23:00 UTC (14:00 HADT) showed a 2-kilometer [1.2 mile] long ash deposit extending southwest from the summit of Great Sitkin Volcano. Additional photographs of the summit area taken from a passing aircraft a week later showed an ash deposit on the snow. This deposit presumably came from the June 10 explosion. \r\nTo characterize the size and progression of the Great Sitkin Volcano explosions, AVO measured the durations of their signals using methodology described by Searcy and Power (2020). Tremor events lasting less than 2 minutes were excluded, though several took place during the unrest. For many of the signals, some uncertainty remains on whether they reflect explosions, short volcanic tremor episodes, or more minor steam bursts. Except for the event on June 10, which produced an identifiable ash deposit, any of these events could have been produced by any of the previously listed mechanisms. \r\n\"In response to the volcanic activity, AVO made four changes to Great Sitkin Volcano’s Aviation Color Code and Volcano Alert Level during 2018. The volcano began the year at YELLOW and ADVISORY, but on January 18, after the number of earthquakes had fallen to background levels, AVO lowered the Aviation Color Code and Volcano Alert Level to GREEN and NORMAL. It raised them again to YELLOW and ADVISORY on June 10 in response to the explosion signal that took place that day. The Aviation Color Code and Volcano Alert Level were lowered back to GREEN and NORMAL on June 27 after declining earthquake activity, then raised to YELLOW and ADVISORY again on July 1 as earthquake activity increased. Great Sitkin Volcano remained at YELLOW and ADVISORY for the rest of 2018.\"\r\nFrom Orr and others, 2023: \"On February 2 [2019], because of declining earthquake activity, the Aviation Color Code and Volcano Alert Level were lowered from YELLOW and ADVISORY, where they had been since July 1, 2018, to GREEN and NORMAL.\"","StartYear":2018,"StartMonth":6,"StartDay":10,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":2,"EndDay":2,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Great Sitkin","ParentVolcano":"Great Sitkin","VolcanoID":"ak111","ParentVolcanoID":"ak111"},{"ID":4846,"Name":"Iliamna avalanches 2018","Description":"From Cameron and others, 2023: \"Like in previous years, Iliamna Volcano experienced at least one large avalanche in 2018, as well as many smaller ones. The Aviation Color Code and Volcano Alert Level at the volcano remained GREEN and NORMAL throughout the year. Late in the morning of July 11, a resident from the Kenai Peninsula observed a fresh slide deposit on the east face of Iliamna Volcano. A retrospective analysis of seismic data indicated a probable avalanche signal at 00:24 UTC on July 11, 2018 (July 10 at 14:24 AKDT). The same resident observed a deposit from a slightly larger avalanche on August 1, 2018, but retrospective seismic analysis did not yield a possible signal for this later event. These deposits are very similar to those of Iliamna Volcano avalanches observed in prior years (Cameron and others, 2020; Dixon and others, 2020).\r\n\"On September 6, 2018, AVO measured the gas emissions at Iliamna Volcano during its annual overflight. These values proved largely unchanged from those of the previous year: instruments recorded an H2 S/SO2 value of about 2, a CO2 / (SO2 +H2 S) value of about 6, and an SO2 emission rate of 45±30 metric tons per day (t/d). The large uncertainty of the SO2 rate is due to a local wind field around the volcano that produces swirling air currents.\"","StartYear":2018,"StartMonth":7,"StartDay":11,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2018,"EndMonth":8,"EndDay":1,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Iliamna","ParentVolcano":"Iliamna","VolcanoID":"ak124","ParentVolcanoID":"ak124"},{"ID":4441,"Name":"Veniaminof 2018/09","Description":"From Cameron and others, 2023: \"The 2018 eruption of Mount Veniaminof took place from early September to late December, ending a roughly 5-year repose since the end of its previous eruption in October 2013 (Dixon and others, 2015). Eruptive activity took place from a ~300-meter-high cone within the summit-defining, ice-filled caldera of Mount Veniaminof. All known historical eruptions have taken place at this cone, although only 5 of the 18 documented historical events produced lava flows. \r\n\"Seismic unrest at Mount Veniaminof began late on September 2, 2018. AVO responded on September 3 by raising the Aviation Color Code and Volcano Alert Level from GREEN and NORMAL to YELLOW and ADVISORY, and on September 4 raised them again to ORANGE and WATCH. Lava fountaining, which likely began as early as September 6, was underway by September 7. By September 14, a lava flow extended about 800 m [2600 ft] down the south flank of the summit cone. This flow eventually covered about 600,000 square meters (m2) [6.5 million square feet (ft2) or 0.23 square miles (mi2)], and intermittent ash emissions reached an altitude of 20,000 ft (6,000 m) ASL. Trace ashfall dusted nearby Perryville, Alaska, 35 km [22 mi] south of the volcano. \r\n\"More details of the 2018 eruption are published in Loewen and others (2022) and Waythomas and others (2022). Information about the 2018 eruption is derived from geophysical instrumentation on or near the volcano, including an 8-station seismic network, regional infrasound sensors, frequent satellite images of the eruption, occasional aerial photographs taken by passing pilots, and webcam images of the volcano from Perryville. Overall, eruptive activity consisted of occasional explosive emissions of ash and steam, episodes of lava fountaining, and the effusion of lava flows. Nearly continuous seismic tremor began at Mount Veniaminof late on September 2, and in response, AVO raised the Aviation Color Code from GREEN to YELLOW and the Volcano Alert Level from NORMAL to ADVISORY the next day. By the early afternoon of September 4, minor ash emissions were apparent in webcam images and were seen by observers in Perryville. This prompted AVO to raise the Aviation Color Code to ORANGE and the Volcano Alert Level to WATCH. \r\n\"Satellite imagery showed a trace amount of ashfall over the southwest sector of the caldera icefield. Webcam images obtained throughout the days of September 4-5 showed distinct, pulsatory ash emissions consistent with small Strombolian explosions. Diffuse ash emissions that reached an altitude of about 10,000-15,000 ft (3,000-4,600 m) ASL were observed by passing pilots on September 5. On September 7, incandescence was observed in early morning webcam images from Perryville, and mid-infrared satellite images showed strongly elevated surface temperatures at the intracaldera cone. These observations indicated that lava fountaining was underway by September 7, though initial lava effusion may have begun as early as September 6. Seismicity at the time was characterized by long-period events and pulsatory tremor bursts, the latter of which lasted as long as a few minutes, though it also included intermittent harmonic tremor (primarily on September 3). The tremor became more continuous around September 7. \r\n\"On September 11, a passing pilot observed and photographed several thin, ribbon-like lava flows, fed by low fountaining or spattering, on the south flank of Mount Veniaminof’s intracaldera cone and coalescing at the cone’s base. A WorldView-3 satellite image acquired on the same day showed lava erupting from as many as four small vents in the same area and feeding a lava flow covering about 50,600 m2 [545,000 ft2]. On September 16 and 18, Sentinel-2 satellite images showed definitive steam emissions associated with lava-ice interaction at the terminus of the lava flow, and on September 25, robust, vertically rising steam emissions associated with lava-ice interaction were evident in Perryville webcam images. Aerial photographs taken on September 26 confirmed that the lava flow had begun melting into the ice and snow on the south side of the intracaldera cone. Conspicuous concentric subsidence cracks grew around the periphery of the lava flow as the glacier responded to this melt-induced loss of mass. \r\n\"Sulfur dioxide emissions were detected near Mount Veniaminof on September 20, 24, and 25 by multiple satellite sensors. The volcano emitted about 500 metric tons (t) [~550 U.S. tons] of SO2 on September 25, whereas emissions detected on September 20 and 24 were barely above background levels. Regional seismic networks detected ground-coupled airwaves on September 25–27, indicating Strombolian explosions were taking place. On September 27, an infrasound array in Dillingham, Alaska (322 km [200 mi] north of the volcano), also recorded explosive signals from the volcano. \r\n\"Lava effusion characterized activity in early October and was associated with continuous tremor, nighttime incandescence, and persistent, strong thermal signals at the intracaldera cone. Measurements from the Ozone Monitoring Instruments (OMI) and the Infrared Atmospheric Sounding Interferometer (OMPS) detected sulfur dioxide emissions on October 4 and 10, but at amounts just above background levels (fig. 5). The total surface area of new lava flows by October 3, as determined from satellite data, was 184,000 m2 [about 2 million ft2]. \r\n\"Visibility improved considerably on October 18 compared to the previous several weeks, allowing a webcam in Perryville to record a billowy, low-altitude ash cloud extending southeast from the intracaldera cone. Several satellites detected SO2 on October 17 and 18, with OMI measuring about 270 t [300 U.S. tons] of SO2 emitted near Mount Veniaminof on October 18. Ash emissions reached an altitude of about 20,000 ft (6,000 m) ASL on October 19, and on October 23, satellite imagery showed minor ash deposits in the summit crater. Trace ashfall was reported in Perryville on October 25. Satellite observations that day indicated that lava had covered a total area of about 385,000 m2 [about 0.15 sqaure miles (mi2)]. The volcano remained restless through the end of October, with continued lava effusion and intermittent minor ash emissions. Sulfur dioxide was again detected in satellite data on October 30 and 31, but in amounts just slightly above background levels. \r\n\"By about November 3, activity at Mount Veniaminof began transitioning to episodic emissions of more robust steam and ash clouds, which appeared in satellite and webcam data. Satellite imagery from the early morning of November 5 showed an eastdrifting ash cloud, confirmed by a pilot’s observation, extending at least 60 km [37 mi] beyond the vent and reaching a maximum altitude of about 14,000 ft (4,300 m) ASL. From November 6 to 19, satellite data and occasional webcam images showed a persistent volcanic cloud of steam and ash extending as far as about 64 km [40 mi] from the intracaldera cone at an altitude that varied from 8,000 to 12,000 ft (2,400 to 3,700 m) ASL. Satellite instruments also detected SO2 near the volcano throughout early to mid-November, though the seasonal decline in ultraviolet light made the detection and accurate estimation of atmospheric SO2 loading less certain. \r\n\"On November 19, volcanic tremor increased in amplitude to reach the highest levels that had been measured up to that point in the eruption. This increase in seismicity was accompanied by infrasound detections on an array in Dillingham, which continued for the next few days. Satellite data from November 19 indicated that lava and tephra from the eruption now covered 540,000 m2 [0.2 mi2]. \r\n\"Conditions at the volcano escalated again on November 21, with increasing ash emissions and tremor amplitudes. An ash cloud detected in satellite imagery now extended more than 240 km [150 mi] southeast from the vent, reaching an altitude of at least 15,000 ft (4,600 m) ASL. This cloud was also observed from Perryville, where residents reported distinct \"booming\" sounds - likely explosions - coming from the direction of the volcano. The level of seismicity and the extent of the ash cloud prompted AVO to raise the Aviation Color Code and Volcano Alert Level to RED and WARNING. \r\n\"Mount Veniaminof emitted ash nearly continuously for much of November 21 as the ash cloud continued lengthening to the southeast, eventually reaching a distance of at least 400 km [250 mi] from the vent. Trace ashfall was again reported at Perryville on November 21 and 22. Activity began to decline by the late afternoon of November 21 (AKST), and on November 22, AVO lowered the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH. Clear webcam views from Perryville on November 22 showed nearly continuous ash emissions extending as far as 100 km [62 mi] beyond the vent and reaching an altitude of about 10,000 ft (3,000 m) ASL. Unobstructed nighttime views showed incandescence at the summit.\r\n\"Coincident with a gradual decline in tremor amplitude, by November 25, ash emissions were no longer evident from the intracaldera cone. On November 27, however, the RSAM of volcanic tremor increased slightly, and AVO detected occasional infrasound pulses on arrays in the Alaskan cities of Dillingham, Sand Point, and Akutan. This slight increase in activity was associated with the appearance of minor ash emissions in satellite data. From November 30 to December 3, data transmission from the Mount Veniaminof remote seismic stations was interrupted, so AVO relied primarily on satellite observations and regional infrasound data to maintain surveillance. During this period, satellite data continued to show elevated surface temperatures, and small volcanic clouds were visible in some images. \r\n\"By December 6, the continuous tremor signal that had been characteristic of the eruption transitioned into frequent long-period (LP) earthquakes. This change likely indicated that lava effusion had paused or ended. Over the next several days, LP earthquakes and tremor bursts lasting as long as tens of seconds took place frequently, along with occasional harmonic tremor. A partly cloudy Sentinel-2 satellite image from December 10 showed that a light snow dusting covered parts of the intracaldera lava flows, and that only minor steam emissions continued. The weakening of seismic activity, absence of continuous tremor, and apparent cooling of the lava flows further indicated that eruptive activity had ceased. \r\n\"AVO detected many ground-coupled airwaves associated with LP earthquakes on December 11, but no other outward signs of unrest were observed in satellite or webcam imagery. This quiescence quickly changed as ash emissions from the intracaldera cone were again observed in Perryville webcam images on December 13 and 16. As cloud cover decreased over the volcano, satellite imagery again showed elevated surface temperatures, indicating a resumption in lava effusion, and also showed small volcanic clouds again extending from the intracaldera cone. This resumption of activity was accompanied by the return of the low-level, nearly continuous seismic tremor, which persisted until December 16, at which point the tremor signal ended and was replaced by many discrete, low-frequency events. Webcam images from Perryville showed minor ash emissions through December 17, after which the volcano was obscured by clouds. Satellite data confirmed that Mount Veniaminof emitted SO2 during the brief unrest in early to mid-December; additional SO2 emissions, possibly from the volcano, were also detected over the Seward Peninsula during this interval, about 966 km [600 mi] to the north. \r\n\"A Sentinel-2 satellite image acquired on December 20, 2018, showed no active lava effusion or additional advancement of the active lava flows. Slight fluctuations in seismic tremor amplitude took place from December 21 to 28, and on December 23, strong thermal signals again appeared in satellite data. From December 23 to 24, AVO observed lava-fountain-associated incandescence in webcam images. This activity was brief, however, and by December 27, all satellite, seismic, and webcam data indicated that active lava effusion had slowed, or perhaps stopped completely. From December 27, 2018, through the end of the year, the level of unrest at Mount Veniaminof gradually declined. \r\n\"By the end of the eruption, new lava flows covered 600,000 m2 [0.23 mi2] of land. This material came from a cluster of small vents on the upper south flank of a cinder cone within the ice-filled caldera. The flows melted into ice and snow, slowly creating melt depressions around their peripheries. However, no unusual water outflows were observed exiting the caldera through its main drainage, located northwest of the cone. The amount of lava and ash erupted from September 7 to December 27, 2018, resulted in the generation of about 1,200,000 cubic meters (m3 ) [42.4 million cubic feet (ft3)] of lava and 20,000-30,000 m3 [706,000-1,06,000 ft3] of ash, though no aircraft reported encountering ash throughout the eruptive period.\"\r\nFrom Orr and others, 2023: \"The activity at Mount Veniaminof during 2019 was mostly associated with a prior eruptive period that took place from early September to late December 2018 (Cameron and others, [2023]). Unrest at the volcano declined gradually after this period until it seemed likely that the eruption had paused or ended. On January 4, 2019, AVO lowered the Aviation Color Code and Volcano Alert Level from ORANGE and WATCH to YELLOW and ADVISORY.\r\n\"Satellite imagery showed slightly elevated surface temperatures on Mount Veniaminof throughout 2019, although cloud cover frequently impeded observations. The elevated surface temperatures were probably associated with the cooling of lava flows emplaced on the intracaldera cone in 2018 (Cameron and others, 2023). Minor steam emissions were occasionally visible in webcam views from nearby Perryville. Seismicity indicative of minor unrest - primarily low-amplitude tremor and discrete events - continued into April 2019 before finally declining to background levels. AVO lowered the Aviation Color Code and Volcano Alert Level to GREEN and NORMAL on April 30, 2019, after about four months with no significant unrest.\"","StartYear":2018,"StartMonth":9,"StartDay":4,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":4,"EndDay":30,"EndTime":null,"EndQualifier":4,"EndQualifierUnit":"Months","Volcano":"Veniaminof","ParentVolcano":"Veniaminof","VolcanoID":"ak301","ParentVolcanoID":"ak301"},{"ID":4853,"Name":"Shrub 2019/03","Description":"From Orr and others, 2023: \"During a field visit to the Klawasi group mud volcanoes in June 2019, AVO scientists found a new extrusion of mud at the base of Shrub mud volcano’s north flank. The extrusion was active during the visit and had started recently, given that evergreens partly buried by the flow were just beginning to turn orange. Satellite imagery indicates this activity probably started between March 7 and March 9. The flows, which came from vents on mud deposits dating to the late 1990s and early 2000s, extended northeast and spread into the adjacent forest to the north. Satellite data showed that the extrusive activity continued until at least October 21 before stopping sometime in the subsequent winter. The vents were inactive by the time satellite views of the area resumed in early February 2020, although new vents had opened immediately south of the old ones.\"","StartYear":2019,"StartMonth":3,"StartDay":8,"StartTime":null,"StartQualifier":1,"StartQualifierUnit":"Days","EndYear":2019,"EndMonth":12,"EndDay":19,"EndTime":null,"EndQualifier":58,"EndQualifierUnit":"Days","Volcano":"Shrub","ParentVolcano":"Klawasi Group","VolcanoID":"ak253","ParentVolcanoID":"ak163"},{"ID":4859,"Name":"Isanotski non-eruptive activity 2019","Description":"From Orr and others, 2023: \"A series of small earthquakes thought to be associated with glacial activity took place near the summit of Isanotski Volcano in the spring of 2019. Around 13,000 earthquakes were detected from March 12 to May 11, forming several swarms that each lasted hours to days. Tremor bursts were also recorded within a few days after some of the swarms. Sporadic seismicity continued into the summer, although this seismicity was less significant than that of the spring. Most earthquakes recorded near Isanotski Volcano in 2019 were too small to be located, so their local magnitudes could not be determined. However, a larger event on May 1 was located close to the surface near the summit of Isanotski Volcano and had an ML of −0.3. These traits are consistent with a glacial seismicity source. Photographs taken in August 2019 show crevasses in the ice on the north side of Isanotski Volcano that may be related to the spring seismicity. \r\n\"The 2019 seismic sequence began on March 12 at 05:20 UTC (March 11 at 21:20 AKDT). For the first four days, the earthquakes in the sequence had low amplitudes, but on March 16, events suddenly increased in amplitude and decreased in rate. These events continued until late on March 21. After a 3-hour pause, in the early morning of March 22, a 4-minute-long tremor burst followed the earthquakes. A second swarm began several hours later and ended on March 25. The seismicity resumed on March 31 with a third earthquake swarm that continued for about a day and a half. This was followed by a series of short tremor bursts and LP earthquakes on April 4. \r\n\"Another series of earthquake swarms, each lasting less than a day, took place on April 12-16. These were followed by a 1.5-minute-long tremor burst on April 18. The last large swarm of the sequence started on April 21 and continued until May 9. Like the opening swarm in March, the earthquakes of this final swarm sharply increased in amplitude after about 5 days. The swarm was also followed by a 6-minute-long tremor burst on May 12. Although the tremor burst concluded the main sequence, tremor was also noted on May 30 and June 1. Occasional earthquakes occurred during the pauses between the March-May swarms, and more occurred afterward until at least July. These sporadic events are difficult to describe thoroughly because they typically had very low amplitudes (which could easily be masked by noise) and because local monitoring is limited.\"","StartYear":2019,"StartMonth":3,"StartDay":12,"StartTime":"05:20:00","StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":7,"EndDay":null,"EndTime":null,"EndQualifier":1,"EndQualifierUnit":"Months","Volcano":"Isanotski","ParentVolcano":"Isanotski","VolcanoID":"ak135","ParentVolcanoID":"ak135"},{"ID":4857,"Name":"Martin non-eruptive activity 2019","Description":"From Orr and others, 2023: \"Although no historical eruptions of Mount Martin are known, its fumarolic field frequently produces towering vapor plumes that can reach as high as 1,000 m above the summit when environmental conditions are right. Such a plume was observed on March 14, as described in two PIREPs released by the Federal Aviation Administration (FAA). The reports, which described steaming to 10,000 ft (3,000 m) from 'a mountain,' were linked to Mount Martin and quickly verified as typical activity for this volcano. \r\n\"Mount Martin showed an increase in seismicity during 2019, although the cause was undetermined. Earthquakes at the volcano are common - AVO typically locates as many as one dozen weekly - but approximately 400 located earthquakes took place in September 2019, a swarm that was the largest at Mount Martin since 2006 (O’Brien and others, 2012). The activity declined to about 100 earthquakes per month in October and November, then returned to background levels in December. Background-level earthquakes at Mount Martin typically cluster at a shallow depth in a diffuse pattern north of the summit. In contrast, the 2019 swarm was located predominantly in the west half of this background cluster zone and at a slightly greater depth. AVO closely monitored Mount Martin’s temporary increase in seismicity but kept the Aviation Color Code and Volcano Alert Level at GREEN and NORMAL throughout the year.\"","StartYear":2019,"StartMonth":3,"StartDay":14,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":12,"EndDay":15,"EndTime":null,"EndQualifier":15,"EndQualifierUnit":"Days","Volcano":"Martin","ParentVolcano":"Martin","VolcanoID":"ak189","ParentVolcanoID":"ak189"},{"ID":4856,"Name":"Iliamna avalanches 2019","Description":"From Orr and others, 2023: \"Although Iliamna Volcano maintained an Aviation Color Code and Volcano Alert Level of GREEN and NORMAL throughout 2019, AVO observed seismicity episodes suggestive of ice and rock avalanches, and two large avalanches were confirmed in satellite images. Avalanches like these are common on Iliamna Volcano, where they are composed mostly of ice and snow (as much as 80 percent by volume) (Schneider and others, 2010), and they are highly mobile, traveling at mean speeds of approximately 50 meters per second (m/s) [110 miles per hour] and reaching peak speeds, estimated via numerical modeling, of more than 70 m/s [160 miles per hour] (Caplan-Auerbach and Huggel, 2007; Schneider and others, 2010). \r\nThe first of the two large ice and rock avalanches took place on the south flank of the volcano in late March. This first avalanche started at an elevation of 2,800 m [9,200 ft] and ran for about 3 km [1.9 mi], reaching a final elevation of 1,450 m [4,760 ft]. A seismic signal inferred to be from the avalanche was detected on stations as far as approximately (~) 100 km [60 mi] away at 18:00 UTC (10:00 AKDT) on March 26, with a recorded duration of 3-4 minutes. This timing for the ice and rock avalanche was roughly confirmed by Landsat satellite images taken before and after the seismic signal, although the signal of the avalanche did not appear in infrasound data. \r\n\"The second, much larger ice and rock avalanche took place on the east flank of Iliamna Volcano at 00:03 UTC on June 21 (June 20 at 16:03 AKDT) (Toney and others, 2021). An oblique aerial photograph taken the same day and Copyright 2019 DigitalGlobe, Google Earth Copyright 2019 DigitalGlobe, Google Earth satellite imagery acquired the next day showed the flow deposit on Iliamna Volcano’s east-facing Red Glacier. Red Glacier has hosted many debris avalanches in prehistoric and historical time (Waythomas and others, 2000); its most recent avalanche of comparable size took place in May 2016. The June 21 rock and ice avalanche initiated less than 1 km [0.6 mi] from the volcano’s summit and traveled east for about 8 km [5 mi]. Measurements taken from satellite imagery estimate that the deposit covered an area spanning approximately 7.1×10^6 m^2 [76,000,000 ft^2]. Assuming an average deposit thickness of 0.5 m, this yields a volume of about 3.6×10^6 m^3 [39,000,000 ft^2]. \r\n\"The second ice and rock avalanche on Iliamna Volcano, like the July 15 ice and rock avalanche on Mount Spurr, generated energetic seismic and acoustic signals that were recorded both locally and regionally (Toney and others, 2021). One local seismic station recorded at least 100 minutes of precursory seismicity (J. Caplan-Auerbach, Western Washington University, written commun., 2019). High-frequency signals associated with the event itself were recorded on local and regional (greater than 100 km [60 mi] away) seismic networks, and LP seismic signals were recorded more than 600 km [370 mi] away. Pre-avalanche seismicity was also documented during Red Glacier avalanches in 1994, 1997, 2003, and 2016 (Caplan-Auerbach and Huggel, 2007; J. Caplan-Auerbach, Western Washington University, written commun., 2016). The infrasound array in Dillingham detected acoustic waves from the event, as did the infrasound arrays in the Alaskan cities of Sand Point and Fairbanks.\"","StartYear":2019,"StartMonth":3,"StartDay":26,"StartTime":"18:00:00","StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":6,"EndDay":21,"EndTime":"00:03:00","EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Iliamna","ParentVolcano":"Iliamna","VolcanoID":"ak124","ParentVolcanoID":"ak124"},{"ID":4511,"Name":"Pavlof 2019 activity","Description":"From Orr and others, 2023: \"In 2019, Pavlof Volcano showed signs of weak activity that caused AVO to raise the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY three times...The first change was made on May 15, 2019, in response to an increase in seismic tremor and webcam images of robust summit degassing. The Aviation Color Code and Volcano Alert Level were lowered back to GREEN and NORMAL on June 12, after activity declined...\r\n\"A total of 90 earthquakes were located within 20 km of Pavlof Volcano during 2019. Of these events, 44 were classified as volcano-tectonic (VT) earthquakes, with a collective depth range of −2.85 to 31.5 km and a local magnitude (ML) range of −0.41 to 1.65. The other 46 were classified as LP earthquakes, with a depth range of 8 to 34 km and a ML range of −0.36 to 1.65. Of the 46 LP events, 21 were located ~5 km northeast of Pavlof Volcano beneath Pavlof Sister, a pattern also seen in the seismicity of previous years (Power and others, 2004b). AVO recorded several tremor episodes at Pavlof Volcano in 2019. There is no obvious temporal relationship between the tremor and the earthquake activity...The activity in 2019 started with weak, intermittent tremor on May 15-19. Two brief tremor signals (~3 minutes each) were then observed on May 29, followed by several brief tremor bursts on May 31...\r\n\"The annual number of earthquakes located at Pavlof Volcano increased between 2017 and 2019. This trend is probably influenced by improvements made to Pavlof Volcano’s seismic network in the summer of 2017, but the fact that AVO located significantly fewer events in 2019 than 2018 suggests a change in activity level unrelated to the network improvements.\"","StartYear":2019,"StartMonth":5,"StartDay":15,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":6,"EndDay":12,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Pavlof","ParentVolcano":"Pavlof","VolcanoID":"ak210","ParentVolcanoID":"ak210"},{"ID":4860,"Name":"Makushin non-eruptive activity 2019","Description":"From Orr and others, 2023: \"Earthquake swarms are common at Makushin Volcano and several took place in 2019. Most swarms consisted of fewer than 10 events each; however, two more prominent swarms (on May 15 and June 18) contained more than 40 events each. Earthquakes in both swarms were located at depths of 5-10 km. The May 15 swarm comprised 45 earthquakes, located 17 km [10.6 mi] east of the volcano’s summit, and the June 18 swarm comprised 66 earthquakes, located 1-3 km southeast of the summit. A third, smaller swarm of 19 earthquakes took place on June 22, at similar depths to the earlier swarms and 11-12 km east-southeast of the summit. The Aviation Color Code and Volcanic Alert Level of Makushin Volcano remained at GREEN and NORMAL throughout the year.\"","StartYear":2019,"StartMonth":5,"StartDay":15,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":6,"EndDay":22,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Makushin","ParentVolcano":"Makushin","VolcanoID":"ak188","ParentVolcanoID":"ak188"},{"ID":4521,"Name":"Great Sitkin 2019 activity","Description":"From Orr and others, 2023: \"AVO identified a single small explosion associated with Great Sitkin Volcano’s seismic unrest [in 2019]. It took place at 05:40 UTC on June 2 (June 1 at 20:40 HADT) and produced an emergent waveform with most of its energy between 1 and 5 hertz, similar to other small explosions recorded at Great Sitkin Volcano since January 2017. The event had a duration of 2 minutes and 17 seconds, determined using the methodology described in Searcy and Power (2020) for calculating the duration of explosions. No associated infrasound signal was observed on the instruments AVO operates in the City of Adak, indicating that the explosion was small...\r\n\"The Aviation Color Code and Volcano Alert Level were elevated...to YELLOW and ADVISORY on June 2, after the identification of the explosion signal recorded June 1. The Aviation Color Code and Volcano Alert Level were lowered again to GREEN and NORMAL on July 15, on the basis of declining seismicity. The Aviation Color Code and Volcano Alert Level remained there through the end of the year...\r\n\"During 2019, AVO located 629 earthquakes at Great Sitkin Volcano, principally clustered within the shallow crust extending from the summit to roughly 10 km [6 mi] deep. Additional shocks were also located between 10 and 35 km [6-22 mi] deep, with waveforms and frequency contents indicating both VT and deep LP events. Local magnitudes of located events ranged from −1.37 to 2.22. The largest event was located roughly 20 km [12 mi] southwest of the summit of Great Sitkin Volcano at a depth of 8.6 km [5.3 mi]. This hypocenter was deeper than those for earthquakes typically associated with volcanic processes beneath the volcano. \r\n\"The Great Sitkin Volcano seismic network experienced several station failures in 2019, impairing AVO’s ability to locate earthquakes. The most notable failure period spanned January to mid-June. These failures are likely the cause of a reduction in the number of located earthquakes in early 2019 relative to 2018, and the cause of an absence of shallow hypocenters detected in the first half of 2019. In response to the failures, AVO carried out a major upgrade to the seismic network in June 2019. The upgrades involved changing most of the older analog stations (installed in 1999) to broadband digital stations, although the analog stations GSSP and GSCK were left in operation for continuity. These network upgrades resulted in significantly improved station performance for the remainder of 2019.\"","StartYear":2019,"StartMonth":6,"StartDay":1,"StartTime":"21:40:00","StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":7,"EndDay":15,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Great Sitkin","ParentVolcano":"Great Sitkin","VolcanoID":"ak111","ParentVolcanoID":"ak111"},{"ID":4541,"Name":"Shishaldin 2019","Description":"From Orr and others, 2023: \"Shishaldin Volcano erupted from July 2019 through the end of the year, with Strombolian explosions, lava flows and lahars on the volcano’s flanks, and sporadic ash clouds. The eruption was the most significant at Shishaldin Volcano since 1999, when an eruption produced Strombolian explosions, lahars, and a subplinian ash cloud that reached 45,000 ft (13,700 m) ASL (Nye and others, 2002; Stelling and others, 2002; McGimsey and others, 2004). Prior to 2019, the most recent eruption to send lava flows down the volcano’s flanks took place in 1955 (Anchorage Daily News, 1955). A questionable news report from 1976 (Andersen, 1976) described lava flows at Shishaldin Volcano that should probably be attributed instead to Pavlof Volcano, which was erupting at that time. Although Shishaldin Volcano erupted from September through October 1975, no lava flows were reported. Thus, the 2019 flows were likely the first on the flanks of Shishaldin Volcano in 64 years and represent a departure from the typical style of its historically observed eruptions. Eruptions at Shishaldin Volcano more commonly consist of Strombolian explosions and lava fountaining within the summit crater. \r\n\"The initial 2019 eruptive activity of Shishaldin Volcano began in July, continued into September, and featured the growth of a small spatter cone in the summit crater. The lava column then withdrew in mid-September, causing the crater floor to collapse and pausing the eruption for approximately one month. Activity resumed in mid-October with a new, rapidly growing spatter cone within the summit crater, while small lava flows spilled out of the crater and ran ~2 km [1.2 mi] down the volcano’s north flank. These flows melted into the snow and ice, producing small lahars that followed drainages north to the Bering Sea. Several collapse events from the summit spatter cone in November and December left lobate flowage deposits on Shishaldin Volcano’s north flank and produced small ash plumes that drifted downwind. Finally, a collapse event on December 12 produced a larger ash plume, which reached an altitude as high as 23,000 ft (7,000 m) ASL, generated three detected lightning strokes, and deposited ash on the southeast flank of the volcano. \r\n\"The following paragraphs describe each phase of the 2019 eruption in greater detail…\r\n\"Eruption Buildup (July 1-July 23) \r\n\"Satellite imagery indicated elevated surface temperatures at Shishaldin Volcano starting July 1, and the brightness temperatures continued increasing for the next two weeks. Tremor and LP earthquakes were also detected during the same period and may have started occurring as early as mid-June. On July 10, field crews noted that the summit plume was unusually vigorous, although no sulfur dioxide (SO2) was detected in satellite data that day. \r\n\"On July 12, an overflight by a crew associated with the Plate Boundary Observatory recorded visible incandescence within the summit crater (K. Austin, University NAVSTAR Consortium [UNAVCO], written commun., 2019). This report, along with increasing surface temperatures detected in satellite data and increased seismic activity, prompted AVO to raise the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY on July 13. Elevated surface temperatures and an increasing amplitude of seismic tremor continued from July 12 to 23. \r\n\"Cone Eruption (July 24-September 19) \r\n\"On July 23, AVO field crews photographed several new volcanic features at the summit of Shishaldin Volcano: a small cone within the summit crater, active lava flowing around the base of this cone, and minor tephra deposits on the inside walls of the crater. The confirmation of active lava at the surface triggered AVO to raise the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH on July 24. Clear, high-resolution satellite images documented the spatter cone as it continued to grow and showed signs of activity through mid-September. These images also showed occasional light ash deposits on the upper flanks of the volcano, but no lava or significant amounts of ash appeared outside the summit crater. \r\n\"Bursts of seismic tremor, thought to be caused by Strombolian explosions, were first detected on July 25 and occurred intermittently through August. This eruptive style was confirmed on August 16 by a passing observation plane operated by the National Oceanic and Atmospheric Administration Alaska Fisheries Science Center, which recorded visible and infrared video of the volcano. Seismic tremor, recorded as real-time seismic amplitude measurements (RSAM), also steadily increased through August, peaked around September 6, and then decreased markedly after September 14. Minor SO2 emissions were detected on August 27-28 and September 2 in sensitive ultraviolet (UV) satellite images (from the TROPOspheric Monitoring Instrument [TROPOMI] on the Copernicus Sentinel-5 Precursor satellite), but not by less-sensitive infrared (IR) satellite sensors (Infrared Atmospheric Sounding Interferometer [IASI] instruments onboard the Meteorological Operational satellite series). The last visual confirmation of eruptive activity at the summit during this period was a Landsat 8 satellite image taken on September 9. \r\n\"Clear, high-resolution satellite images showed that the spatter cone continued growing with signs of activity through mid-September, although it remained confined within the summit crater. Besides the occasional dusting of light ash on the upper flanks of the volcano, no lava or significant amounts of ash were deposited outside the crater. \r\n\"Pause (September 19-October 13) \r\n\"On September 19, the spatter cone, which had grown since July, collapsed into the crater. The event was recognized during a retrospective analysis of borehole tiltmeter data from stations installed on the flanks of Shishaldin Volcano by the UNAVCO Plate Boundary Observatory. This collapse was the largest-amplitude tilt signal recorded during the eruption and is interpreted to reflect the drainage of magma from the conduit. \r\nAlthough cloudy conditions blocked satellite views at the time of the collapse event, clear satellite images taken on September 23 showed reduced mid-IR signatures, indicating lower surface temperatures and a lack of significant eruptive activity. More satellite images taken on September 26 confirmed the crater floor had collapsed and that no evidence of ongoing eruptive activity remained. As a result, on September 26, AVO downgraded the Aviation Color Code and Volcano Alert Level to YELLOW and ADIVSORY. The lack of eruptive activity and the collapse of the cone were again confirmed in a clear, high-resolution satellite image taken on October 3. \r\n\"Renewed Eruption; North Flank Lava Flows and Lahars; Cone Collapses (October 13-End of Year) \r\n\"On October 13, satellite imagery showed an increase in surface temperatures at Shishaldin Volcano, signaling renewed eruptive activity. More satellite observations from October 17 confirmed the growth of a new spatter cone within the summit crater. In response, AVO changed the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH later that day. Activity at the volcano escalated rapidly, as indicated by the detection of Strombolian explosions in infrasound data, observations of incandescence in webcam images, the detection of SO2 emissions in satellite data, and an increase in seismic tremor. Infrasound signals were first recorded on October 18 and took place at 15-30-second intervals by October 21. The first observation of incandescence at Shishaldin Volcano during this period was made from a webcam on the southwest flank of Isanotski Volcano during the night of October 19-20. On October 21, satellite TROPOMI sensors detected SO2 emissions, and AVO recorded a spike of seismic tremor at the volcano. This first tremor spike, as well as subsequent ones, was characterized by RSAM values that increased slowly over several days and sharply decreased over several hours, resulting in a 'shark fin' pattern.\r\n\"On October 24, during another seismic tremor peak, a clear satellite image captured an active, 800-meter-long lava flow traveling down the northwest flank of Shishaldin Volcano. The flow melted snow and ice, generating a lahar that had traveled ~3 km [~2 mi] down drainages to the north. In addition, minor ash deposits were seen on snow 8 km [5 mi] southeast of the summit in the image. The same day, an anonymous pilot of a passing airplane reported to AVO the presence of clouds over the volcano that looked like 'smoke rings.' The regional infrasound array at Sand Point, Alaska, detected clear explosions associated with this activity. \r\n\"Cyclic increases in seismic tremor, presumably from Strombolian-type explosions, were accompanied by ash and gas emissions and continued to take place through the end of 2019. Observers on a passing U.S. Fish and Wildlife Service flight and AVO field crews on Unimak Island confirmed this Strombolian-type explosive behavior on November 11 and December 20, respectively. At times of increasing tremor amplitude and when viewing conditions permitted, active lava flows on the north flank of the volcano were seen in satellite and webcam views and by observers in the City of Cold Bay. Infrared satellite sensors also detected an increase in radiative power at the volcano, reflecting the increased effusive activity. \r\n\"In partnership with UNAVCO, AVO scientists experimented with recording high-rate tilt data (1 sample per second) using the tiltmeter at station AV36, located on the western margin of Shishaldin Volcano. The instrument detected several episodes of explosive activity at the summit while recording at this sampling rate; during each episode, the data showed an hours-long increase in amplitude culminating in several hours of high-amplitude activity bursts. Ground motions during these events were generally tangential to the edifice. These data show that open-system volcanoes like Shishaldin Volcano generate appreciable ground deformation over timescales and at amplitudes that can be recorded by borehole tiltmeters.\r\n\"During the summer and early fall of 2019, only UV satellite instruments, such as TROPOMI, detected SO2 at Shishaldin Volcano as a result of their higher sensitivity than IR sensors. Detections from these instruments stopped in November, however, as the available UV light decreased. In contrast, IR SO2 sensors, such as IASI sensors, although less sensitive, do not lose effectiveness in the winter. IASI sensors began detecting SO2 from Shishaldin Volcano on October 28, and these detections continued in November and December. Considering the lower sensitivity of satellite IR to SO2, the IASI detections indicate that gas emissions were higher at the end of the year than earlier in the eruption. \r\n\"After each tremor and emission spike, activity quickly decreased and clear satellite images showed a pause in lava effusion. Synthetic Aperture Radar (SAR) images from the TerraSAR-X and TanDEM-X satellites, provided during the eruption by S. Plank (German Aerospace Center), indicated that the summit spatter cone experienced partial collapses during many of these episodes. Collapse events were specifically noted on November 11, November 23, December 5, and December 12. Lobate flowage deposits appeared downslope from the cone after each event. \r\n\"The largest of these collapse events, which took place on December 12 at 16:10 UTC, was detected in seismic and infrasound data, webcam photos, and satellite imagery. Photographs of the volcano after the event showed an ash cloud reaching an altitude of about 25,000 ft (7,600 m) ASL. Three lightning strokes were also detected from this cloud. Unlike other collapse events, the December 12 event was followed by elevated tremor and continued lava effusion, the latter of which was visible in satellite images and in photographs taken from the City of Cold Bay. This event was associated with the largest ashfall of 2019, although only a minor amount of ash was deposited on the southeast flank of Shishaldin Volcano. \r\n\"A field crew visited Shishaldin Volcano on December 20, 2019, and although the lava flows were inactive during the visit, the vent itself was producing regular Strombolian explosions. The crews sampled the December 12 ash deposit, later analysis of which determined the tephra to be a mix of lithic, tachylite, and sideromelane grains. The sideromelane grains were basaltic, with glass composed of ~52 weight percent SiO2 and minerology consisting of plagioclase, olivine, and magnetite, although only plagioclase and olivine existed as larger (greater than 0.1 millimeter [0.004 inch]) phenocryst phases. The high proportion of tachylite and lithic grains in the tephra supports a cone-collapse origin for the deposit - the composition indicates a high proportion of the material was mobilized from previously deposited and cooled grains. \r\n\"The next active lava effusion periods were noted on December 21 and December 26 (after the December field visit). Cloudy conditions generally obscured activity at Shishaldin Volcano during the last few days of the year, but eruptive activity continued into January 2020. \r\n\"Although the 2019 eruption deposited only minor amounts of ash on the flanks of Shishaldin Volcano, the lava flows from the event extended 1-2 km [0.6-1.2 mi] down its north flank. Associated lahar deposits traveled even farther, reaching as far north as the Bering Sea. The lava flows of 2019 were the first historically well-documented ones at Shishaldin Volcano and likely represented the first lava flow activity outside its summit crater in more than 60 years.\"\r\nFrom Orr and others, 2024: \"Shishaldin Volcano erupted from July 2019 to March 2020. The 2019 activity was documented in Orr and others (2023) and the 2020 activity is documented herein…\r\n\"Ash-Rich Paroxysm Sequence (January 1–20) \r\n\"Eruptive activity at the start of 2020 followed a similar pattern to that established in November 2019: seismic tremor and lava flow activity generally increased over a period of several hours before abruptly shutting down in days-long pauses. Unlike activity in the prior weeks, however, three periods of escalating activity in January culminated in increased ash emissions, prompting AVO to issue a Volcanic Activity Notice (VAN) each time.\r\n\"Shishaldin Volcano began 2020 with an Aviation Color Code and Volcano Alert Level of ORANGE and WATCH. Elevated surface temperatures visible in satellite data on January 2 suggested that weak eruptive activity, confined to the vent, was occurring. Seismicity began to increase on January 3, indicating increasing eruptive activity. This was confirmed by a passing pilot, who reported a clear view of lava fountaining and a robust, steam-rich plume that probably contained some ash from the fountaining. At the same time (starting around 19:00 UTC [10:00 AKST]), satellite views and additional PIREPs recorded ash-poor plumes from the volcano that may have reached as high as ~24,000 ft (~7,300 m) ASL. The fountaining at Shishaldin Volcano was associated with increasing seismic tremor and the emplacement of lava flows mostly concentrated on the volcano’s northwest flank. AVO issued a VAN at 20:38 UTC (11:38 AKST) but did not change the Aviation Color Code or Volcano Alert Level. \r\n\"Seismic tremor decreased sharply at 20:48 UTC (11:48 AKST), and at about the same time, a PIREP indicated that the plume height had risen to ~27,000 ft (~8,200 m) ASL. Volcanic lightning was detected at 21:07 UTC (12:09 AKST), suggesting that the concentration of ash in the plume had increased. These ash emissions did not last long; the concentration was decreasing by 21:30 UTC (12:30 AKST). A WorldView-2 satellite image acquired at 22:22 UTC (13:22 AKST) revealed the state of the volcano: the lava flows active earlier in the day had stalled and were cooling, new lobate pyroclastic flow deposits had been emplaced on the west and south flanks, and an ash-rich plume was drifting southeastward. The new pyroclastic flow deposits were the first to affect the south flank of the volcano during this eruption; prior deposits were restricted to the north flank. Deposition on the west and south flanks of the volcano required overtopping the topographic high point of the summit crater, suggesting they were deposits from the collapse of an ash column as opposed to debris from a tephra cone collapse. Eruptive activity associated with the January 3 event was not observed directly afterward. Lava flow activity at Shishaldin Volcano increased again after January 3, and by January 6, incandescent flows were visible from the City of Cold Bay. The frequent detection of infrasound signals suggested the occurrence of Strombolian explosive activity. Seismic tremor, already elevated, began increasing further on the morning of January 7, and starting around 16:00 UTC (7:00 AKST) that morning, a plume reaching an altitude of ~20,000 ft (~6,100 m) ASL was detected in satellite data. Strong mid-infrared satellite signatures accompanied the plume, suggesting ongoing lava effusion and vigorous lava fountaining, similar to the behavior seen on January 3. A VAN noting this increased activity was issued at 18:39 UTC (9:39 AKST), although the Aviation Color Code and Volcano Alert Level were not changed. At ~20:00 UTC (~11:00 AKST), the seismic tremor started to decline, followed by the detection of volcanic lighting at 20:25 UTC (11:25 AKST). Satellite images acquired shortly afterward indicated that the plume had become more ash-rich and now reached an altitude as high as ~27,000 ft (~8,200 m) ASL, although tremor remained low. These observations prompted AVO to increase the Aviation Color Code and Volcano Alert Level to RED and WARNING at 21:33 UTC (12:33 AKST). Light ashfall from this event was reported in the City of Cold Bay.\r\n\"The plume appeared to have detached from the vent by 22:00 UTC (13:00 AKST), indicating that ash emission had slowed or stopped. The Aviation Color Code and Volcano Alert Level were subsequently lowered to ORANGE and WATCH on January 8 at 04:17 UTC (January 7 at 19:17 AKST). Synthetic aperture radar images acquired later that day showed that the crater had deepened, and the cone had subsided or collapsed. Like the January 3 event, the January 7 paroxysm was followed by a period of quiescence. The only activity detections at Shishaldin Volcano over the next week were infrasound signals consistent with Strombolian activity on January 10. On January 14, a clear WorldView-2 satellite image showed no volcanic activity within the summit crater or on the flanks.\r\n\"Eruptive activity increased again on January 18; lava flows were visible on the volcano flanks and seismic tremor intensified. At 17:18 UTC (08:18 AKST), a pilot reported visible lava but no ash emissions. Observers in the Cities of Cold Bay and King Cove, Alaska, documented the incandescent lava flow during clear weather that evening. Overnight webcam images from the south flank of Isanotski Volcano also showed lava fountaining, and by January 19 at 9:30 UTC (00:30 AKST), satellite images showed an ash-poor gas plume rising as high as ~18,000 ft (~5,500 m) ASL. The level of activity continued to increase, and as a result, the Aviation Color Code and Volcano Alert Level were increased to RED and WARNING at 17:28 UTC (08:28 AKST). By this point, a continuous, 150-kilometer-long plume was visible in satellite images. PIREPs at 18:15 UTC (09:15 AKST) described ongoing lava flow activity and measured that the plume had reached an altitude of ~25,000 ft (~7,600 m) ASL. Over the following hours, seismic tremor continued to increase and trace ashfall was reported in the City of False Pass, Alaska, 38 km northeast of Shishaldin Volcano. A WorldView-2 image captured activity at the vent during this period. Another PIREP at 21:42 UTC (12:42 AKST) indicated that the plume had climbed to ~30,000 ft (~9,100 m) ASL.\r\n\"The seismic tremor dropped precipitously just after 00:00 UTC on January 20 (January 19 at 15:00 AKST). Satellite data acquired about an hour later showed that the plume had transitioned to a more ash-rich composition, a change confirmed by PIREPs. Ash emissions continued for the next several hours. Then, shortly before 05:00 UTC (20:00 AKST), ash emissions stopped and the plume detached from the vent. With the cessation of eruptive activity at the vent, AVO lowered the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH at 09:37 UTC (00:37 AKST).\r\n\"Prolonged Eruption Hiatus (January 20–March 11)\r\n\"Satellite data after the January 20 paroxysm showed new ash deposition—the ash-poor lava fountaining phase produced trace deposits extending northeastward toward False Pass, whereas the later ash-rich phase produced more substantial deposits extending southeastward. Satellite radar imagery also showed that the volcano crater was larger and deeper after the event. The last detected infrasound and seismic event of note during this period was on January 24, and a WorldView-3 satellite image from January 25 showed no visible eruptive activity. Some discreet seismic events and infrasound signals were detected occasionally later on, but these did not build to a clear eruptive signal like that which followed the eruption events earlier in January. On February 7 at 01:20 UTC (February 6 at 16:20 AKST), the Aviation Color Code and Volcano Alert Level were lowered to YELLOW and ADVISORY. No other significant activity was detected at the volcano in February, and clear satellite images showed quiet conditions consisting of minor steaming at the vent and cooling lava flow deposits on the flanks.\r\n\"Final Renewed Eruption (March 11–31)\r\n\"After weeks of quiescence, eruptive activity resumed in March 2020, although it was contained within the summit crater. The first indication of renewed activity appeared in a WorldView-2 satellite image from March 11 that showed a small area of recent ash deposits near the summit crater. The inside of the crater was mostly obscured by steam in the image, but it was generally similar to its appearance in other high-resolution satellite images from February. In the following days, mid-infrared satellite images began to show increased surface temperatures at the volcano. A WorldView-3 image from March 14 showed a saturated short-wave infrared signature at the summit, indicating that lava was erupting again within the summit crater. In response, AVO increased the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH on March 15 at 6:31 UTC (22:31 AKDT on March 14).\r\n\"During the following few weeks, seismicity was elevated and small explosions (probably from Strombolian activity) were detected occasionally in infrasound data. Satellite radar images suggested renewed cone growth, although all eruptive activity was confined within the summit crater. Another WorldView-3 image from March 22 showed activity similar to that on March 14. \r\n\"Seismicity declined thereafter through the end of the month, and an April 1 satellite image showed only a steam plume and no evidence of a heat source, suggesting the eruption had ended. On April 2, a clear satellite image with an unobscured view into the summit crater confirmed that no eruptive activity was occurring. Due to an absence of activity, AVO lowered the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY on April 16 at 19:44 UTC (11:44 AKDT).\r\n\"Aftermath (April 1–End of Year)\r\n\"Low-level unrest continued at Shishaldin Volcano for months after its 2019–2020 eruption. Elevated surface temperatures continued appearing in satellite images, and frequent satellite detections of SO2 were made in late April and May. These SO2 detections also coincided with the increasing ultraviolet radiation of long summer days, which raises the sensitivity of the TROPOspheric Monitoring Instrument (TROPOMI), a satellite instrument used for these detections. Other remote sensing observations made during this period of low-level unrest indicated that magma was still stored shallowly within the conduit, enabling magma degassing, high temperatures, and minor collapse events within the summit crater.\r\n\"On June 24 at 20:00 UTC (12:00 AKDT), the Aviation Color Code and Volcano Alert Level were lowered to GREEN and NORMAL, reflecting an overall decrease of activity to background levels at the volcano, although AVO continued recording evidence of additional minor collapse events using satellite radar images. Some of these events appeared to produce trace ash deposits on the upper flanks, as seen on April 29 and May 7. AVO workers carrying out annual geophysics station maintenance in August and September did not observe any eruptive activity, but helicopter gas surveys at the same time detected continued SO2 degassing at an emission rate of 100±30 metric tons per day. The surveys also measured high carbon dioxide concentrations relative to measurements from 2015 and 2019, which indicated a new deep magma input into the system.\r\n\"Final Deposits and Samples\r\n\"The 2019–2020 eruption of Shishaldin Volcano resulted in (1) many lava flows on the north flank of the volcano, (2) pyroclastic flow deposits related to cone collapse events in December and three eruption paroxysms in January, and (3) lahars that inundated drainages north of the volcano and reached the Bering Sea coast. Accurate mapping of the lava flows was difficult because of poor orthorectification in many of the available high-resolution satellite images, in turn caused by the typically oblique image viewing angles and the steep flanks of Shishaldin Volcano. \r\n\"Satellite images taken on January 14 and January 25 provided close-to-nadir images (11º and 17º off nadir, respectively) that allowed the final deposits to be mapped with reasonable accuracy. The lava flows covered less than 0.9 square kilometers (km2) and extended as far as 3 km from the vent, primarily occupying three distinct drainages, with each new flow burying the previous one. The pyroclastic flow and lahar deposits were gradational and, in many places, difficult to distinguish from each other in satellite images. Deposits on the volcano’s south flank, especially those from the January 3 paroxysm, were likely all pyroclastic flows generated from ash column collapse that overtopped the high point on the crater rim. The lahars and pyroclastic flows to the north were intermixed, forming lobate deposits on the flatter plains north of the volcano. The deposits suspected to be pyroclastic flows generally extended no more than 3 km from the summit vent, whereas lahars followed drainages and traveled farther, some reaching all the way to the coast (more than 30 km north of the summit). Because of the difficulty in distinguishing between pyroclastic and lahar deposits using satellite images alone, they are mapped as a single unit in figure 14 [in original].\r\n\"Only a few samples are available from the 2019–2020 eruption. Samples of a tephra deposit from a cone collapse event, collected by field crews on December 20, 2019, are described in Orr and others (2023). AVO field crews also sampled the toe of a lava flow on the northeast flank of the volcano in 2022; this sample is currently being studied. Community members in the City of Cold Bay collected ash from the paroxysm of January 7, 2020; others in False Pass collected ash from the early stage of the January 19 paroxysm. Both of these samples were dominated by roughly equal parts (1) juvenile, highly fluidal and glassy sideromelane grains and (2) partially devitrified tachylite grains (classifications by Loewen and others, 2021). However, the samples also contained phenocrysts of plagioclase and olivine, along with microlites of plagioclase, olivine, and magnetite. The glass composition was basaltic and was similar to samples from the 1999 eruption (Stelling and others, 2002).\"","StartYear":2019,"StartMonth":7,"StartDay":12,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2020,"EndMonth":6,"EndDay":24,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Shishaldin","ParentVolcano":"Shishaldin","VolcanoID":"ak252","ParentVolcanoID":"ak252"},{"ID":4854,"Name":"Spurr non-eruptive activity 2019","Description":"From Orr and others, 2023: \"On July 15, 2019, at 16:32 UTC (08:32 AKDT), a large ice and rock avalanche took place on the southeast flank of Mount Spurr. A retrospective analysis of satellite imagery indicated the starting zone of the avalanche was less than 1 km from the summit of the volcano. Clear satellite images of the flow deposit showed that it widened before splitting into two lobes that flowed around an elevated lateral moraine dividing the west and east branches of K’idazq’eni Glacier (March and others, 1997; Molnia, 2008). One lobe flowed down the west branch between the moraine and the Crater Peak cone, while the other traveled slightly farther down the east branch of the glacier. Satellite imagery indicated the ice and rock avalanche spanned an area of approximately 2.3×10^6 square meters (m2) [25,000,000 square feet]. Assuming an average deposit thickness of 0.5 m [1.6 feet] yields a volume of about 1.2×10^6 cubic meters (m3) [42,000,000 cubic feet]. \r\n\"The ice and rock avalanche generated energetic seismic and acoustic signals, recorded both locally and regionally. High-frequency signals were detected on the local seismic network and long-period (LP) seismic signals were recorded more than 700 km [435 mi] away. Several local seismic stations also recorded approximately 10 minutes of precursory seismicity. Pre-avalanche seismicity has been previously documented at Iliamna Volcano (Caplan-Auerbach and Huggel, 2007). In addition to the recordings of seismic signals, an infrasound array in Dillingham, Alaska, detected acoustic waves from the event. \r\n\"During an overflight on August 27, AVO staff noted the terrain of the source area consisted of exposed 'slope-parallel lava, with rivulets of meltwater running on its surface.' They found no evidence of increased non-meteorological heating at the summit area (a phenomenon which can trigger ice and rock avalanches) and observed nothing unusual on the other flanks of the summit cone (M. Coombs, USGS, written commun., 2019). The July 15 avalanche took place in an area known for debris flows, as documented by Coombs and others (2006), but previous flows were smaller and more water-rich than the July 15 event. Mount Spurr remained at an Aviation Color Code and Volcano Alert Level of GREEN and NORMAL throughout 2019.\"","StartYear":2019,"StartMonth":7,"StartDay":15,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":7,"EndDay":15,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Spurr","ParentVolcano":"Spurr","VolcanoID":"ak260","ParentVolcanoID":"ak260"},{"ID":4641,"Name":"Semisopochnoi 2019/7","Description":"From Orr and others, 2023: \"Activity at the north cone of Mount Young, which began in September 2018, continued in 2019 with sporadic eruptive activity. Seismic tremor and explosion signals captured most of this activity, along with infrequent infrasound detections and occasional satellite observations of steam and small ash deposits. Although the eruptive style and geophysical characteristics of the 2019 unrest were similar to those of 2018, AVO’s ability to observe them in real time was limited for the first half of the year owing to a prolonged data outage. This outage, caused by a communication failure at the regional data network telemetry hub in Amchitka, lasted from November 2018 to June 2019, at which point communications were restored and the missing data were recovered. \r\n\"Owing to the data outage, the first activity observed at the volcano in 2019 comprised satellite observations of steam in January and a small ash deposit on June 2. Although the north crater of Mount Young has persistently steamed since 2018, the ash deposits observed on June 2 appear to be a more recent change, having followed tremor bursts in mid-May that probably correspond to when they erupted. AVO began receiving seismic data again on June 11 but kept the Aviation Color Code and Volcano Alert Level at UNASSIGNED until early July, when increased tremor prompted a change to YELLOW and ADVISORY. On July 18, the detection of SO2 emissions in TROPOMI satellite data and the recording of ground-coupled airwaves triggered AVO to raise the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH. SO2, steam plumes, ground-coupled airwaves, and infrasound were detected throughout the summer, but no ash deposits were observed. After a period of quiescence, AVO lowered the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY on September 18. \r\n\"Beginning on December 7, the detection of many explosions by regional infrasound sensors indicated a renewal of activity at Semisopochnoi Island, triggering AVO to raise the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH. In addition to producing infrasound, the explosions were accompanied by ash emissions visible in satellite imagery, ground-coupled airwaves, and one SO2 detection (on December 12). No ash plumes reaching altitudes greater than 10,000 ft (3,000 m) ASL and no large ash deposits were observed during this eruptive period. The last activity recorded at the volcano in 2019 was an infrasound detection on December 18. On January 9, 2020, AVO lowered the Aviation Color Code and Volcano Alert Level back to YELLOW and ADVISORY.\"\r\nFrom Orr and others, 2024: \"The overall seismicity remained elevated, however, and on February 15, a series of small explosions and tremor bursts were detected. No ash emissions or deposits were identified in satellite imagery, which was frequently cloudy, but the seismic activity led AVO to return the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH. Seismicity did not increase further and clear imagery later confirmed the volcano was not erupting, although steam emissions were visible. On February 26, AVO lowered the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY.\r\n\"Activity in mid-March was characterized by nearly continuous tremor and frequent, small explosion signals, but no observations of ash plumes. Regional infrasound arrays detected an explosion at the volcano on March 11, followed by more on March 15-16, all of which were accompanied by ground-coupled airwaves recorded on the local seismic network. During this March explosive period, a dark ash deposit appeared around the north cone of Mount Young and TROPOMI imagery showed a possible SO2 plume. In response to the infrasound and remote sensing observations, AVO raised the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH on March 16. This activity was short-lived; by March 22, a partly cloudy WorldView-1 image showed that a robust steam plume emanated from the north cone of Mount Young and a water lake had appeared deep within its crater. After two weeks with no sign of eruption activity, AVO lowered the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY on April 1, 2020.\r\n\"The volcano emitted steam and SO2 regularly throughout the spring and summer, and by June 15, the crater lake had mostly dried up. Planet Labs and Sentinel-2 satellite imagery from June 21 captured an ash deposit extending nearly 4 km [2.5 mi] southward from the north cone crater, accompanied by robust steam emissions and a high-temperature short-wave infrared anomaly within the crater. The appearance of this deposit was associated with ground-coupled airwaves detected on June 16 and 17, but no infrasound. Seismicity at the volcano initially remained elevated, appearing as low-level tremor and small earthquakes, but AVO detected no further explosions in 2020 and its activity waned in the fall. An outage of local real-time monitoring data began on November 11, 2020. Considering the absence of data, the lack of eruptive activity detected since June, and the decaying trend in seismicity, AVO changed the Aviation Color Code and Volcano Alert Level of Semisopochnoi Island to UNASSIGINED on November 20, 2020.\"","StartYear":2019,"StartMonth":7,"StartDay":18,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2020,"EndMonth":6,"EndDay":15,"EndTime":null,"EndQualifier":7,"EndQualifierUnit":"Days","Volcano":"Mount Young","ParentVolcano":"Semisopochnoi","VolcanoID":"ak44","ParentVolcanoID":"ak248"},{"ID":4551,"Name":"Veniaminof 2019 activity","Description":"From Orr and others, 2023: \"On August 1, 2019, AVO received a PIREP of steaming at Mount Veniaminof’s intracaldera cone, which coincided with a weak tremor signal. These observations marked a small but distinct departure from the background level of unrest at the volcano, and as a result, AVO raised the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY. Weak seismicity and occasional long-period earthquakes continued intermittently throughout most of August, but by the end of the month, the volcano returned to its background activity level. AVO subsequently lowered the Aviation Color Code and Volcano Alert Level to GREEN and NORMAL on August 25, 2019. No additional unrest took place at Mount Veniaminof for the remainder of 2019.\"","StartYear":2019,"StartMonth":8,"StartDay":1,"StartTime":"14:21:00","StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":8,"EndDay":25,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Veniaminof","ParentVolcano":"Veniaminof","VolcanoID":"ak301","ParentVolcanoID":"ak301"},{"ID":4855,"Name":"Redoubt non-eruptive activity 2019","Description":"From Orr and others, 2023: \"Although no eruptive activity was detected at Redoubt Volcano in 2019, on August 16, strong winds entrained and resuspended ash near the volcano. The resuspended ash cloud was not seen in satellite imagery but was visible in webcam views, and PIREPs described it as reaching an altitude as high as 10,000 ft (3,000 m) ASL. The National Weather Service Alaska Aviation Weather Unit issued a significant meteorological weather advisory for aviators, but AVO received no reports of ashfall. The Aviation Color Code and Volcano Alert Level at Redoubt Volcano remained GREEN and NORMAL throughout 2019.\"","StartYear":2019,"StartMonth":8,"StartDay":16,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":8,"EndDay":16,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Redoubt","ParentVolcano":"Redoubt","VolcanoID":"ak231","ParentVolcanoID":"ak231"},{"ID":4561,"Name":"Pavlof 2019","Description":"On October 19, AVO raised the Aviation Color Code and Volcanic Alert Level at Pavlof to YELLOW/ADVISORY. From the Volcano Observatory Notice for Aviation: \"Small explosion signals from Pavlof have been detected on the infrasound network located at Sand Point and on the local seismic network today. The volcano is currently obscured by clouds in satellite images. It is unknown if the explosions produced any volcanic ash, but their small size suggests any hazard is currently confined to the area around the volcano's summit. Because these signals are above normal background for Pavlof, the Alaska Volcano Observatory is raising the Aviation Color Code to YELLOW and the Alert Level to ADVISORY.\" On November 6, 2019, AVO lowered the Aviation Color Code and Volcano Alert Level to GREEN/NORMAL, citing no additional signs of unrest after the explosion signals on October 19.\r\nFrom Orr and others, 2023: \"In 2019, Pavlof Volcano showed signs of weak activity that caused AVO to raise the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY three times...They were raised...to YELLOW and ADVISORY on October 19 when small explosion signals were detected by the infrasound array in Sand Point and on the local seismic network, then were lowered back to GREEN and NORMAL on November 6...\r\n\"A total of 90 earthquakes were located within 20 km of Pavlof Volcano during 2019. Of these events, 44 were classified as volcano-tectonic (VT) earthquakes, with a collective depth range of −2.85 to 31.5 km and a local magnitude (ML) range of −0.41 to 1.65. The other 46 were classified as LP earthquakes, with a depth range of 8 to 34 km and a ML range of −0.36 to 1.65. Of the 46 LP events, 21 were located ~5 km northeast of Pavlof Volcano beneath Pavlof Sister, a pattern also seen in the seismicity of previous years (Power and others, 2004b). AVO recorded several tremor episodes at Pavlof Volcano in 2019. There is no obvious temporal relationship between the tremor and the earthquake activity...The activity of 2019 ended with additional tremor pulses that took place on October 18 and December 14.\r\n\"The annual number of earthquakes located at Pavlof Volcano increased between 2017 and 2019. This trend is probably influenced by improvements made to Pavlof Volcano’s seismic network in the summer of 2017, but the fact that AVO located significantly fewer events in 2019 than 2018 suggests a change in activity level unrelated to the network improvements.\"","StartYear":2019,"StartMonth":10,"StartDay":19,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":10,"EndDay":19,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Pavlof","ParentVolcano":"Pavlof","VolcanoID":"ak210","ParentVolcanoID":"ak210"},{"ID":4571,"Name":"Cleveland 2019/11","Description":"From Orr and others, 2023: \"Thermal anomalies and a small summit steam plume appeared occasionally in satellite imagery over the following several months. Clear satellite views in August 2019 showed that a pit, centered on the January dome, had formed since February. More satellite imagery acquired in early November indicated uplift of the new summit dome. Because this uplift was coincident with an apparent increase in the brightness of the summit thermal anomaly and a more robust steam plume, AVO raised the Aviation Color Code and Volcano Alert Level to ORANGE and WATCH. Subsequent satellite imagery, however, showed that the uplift was an artifact from the satellite viewing angle and was not real. The Aviation Color Code and Volcano Alert Level for Mount Cleveland were returned to YELLOW and ADVISORY on November 15, where they remained for the rest of the year. The repose period of 2019 marked the longest at Mount Cleveland since its onset of eruptive activity in 2001.\"\r\nFrom Orr and others, 2024: \"The character of volcanic activity at Mount Cleveland in late 2019 - low seismicity, occasional thermal anomalies, and a small summit steam plume (Orr and others, 2023) - carried over into 2020, and Mount Cleveland began the year at an Aviation Color Code and Volcano Alert Level of YELLOW and ADVISORY. No changes within the summit crater were observed during the first several months of the year; elevated surface temperatures and a weak steam plume were observed sporadically during periods of clear weather. The low level of thermal activity was corroborated by high-resolution satellite imagery in April and May that showed a partly snowcovered dome, suggesting the surface was cold. \r\n\"Because of the apparent quiescence at Mount Cleveland, its Aviation Color Code and Volcano Alert Level were changed to UNASSIGNED on May 7 at 23:37 UTC (14:37 HADT).\"","StartYear":2019,"StartMonth":11,"StartDay":7,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2019,"EndMonth":11,"EndDay":15,"EndTime":null,"EndQualifier":1,"EndQualifierUnit":"week","Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":4611,"Name":"Great Sitkin activity 2020","Description":"From Orr and others, 2024: \"In late July 2016, Great Sitkin Volcano entered a period of increased unrest characterized by an elevated frequency of earthquakes, anomalous steaming from its summit crater, and small explosive events (Dixon and others, 2020). Similar small earthquakes and steaming from the summit crater continued throughout 2020. \r\n\"AVO located 3,393 earthquakes at Great Sitkin Volcano during 2020, a large increase from earlier years. This increase may, in part, reflect network upgrades made during the 2019 field season that replaced older analog sensors with broadband sensors capable of digital telemetry. This new instrumentation has proven more reliable at Great Sitkin Volcano than the older equipment, improving AVO’s ability to detect and locate earthquakes in the area. \r\n\"In late January 2020, Great Sitkin Volcano began to experience an increase in earthquake activity that was interpreted as unrelated to the recently improved seismic detection capabilities, prompting AVO to raise the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY on February 26. This activity peaked in late March and then slowly declined throughout the remainder of 2020. In response to the declining rates of seismicity, the Aviation Color Code and Volcano Alert Level were lowered back to GREEN and NORMAL on October 21. No seismic or infrasound signals indicative of explosive events were detected at the volcano during 2020. \r\n\"The hypocenters of earthquakes at Great Sitkin Volcano in 2020 were principally clustered within the shallow crust, extending from the summit to roughly 10 km [6 mi] depth below sea level. Earthquakes were also recorded at depths between 10 and 35 km [6 and 22 mi]; these had waveforms and frequency contents suggesting both volcano-tectonic (VT) and deep LP events. Located events ranged in magnitude from ML -1.2 to ML 3.5. The ML 3.5 event occurred on March 6 (at 15:31 UTC; 05:31 HAST) under the east rim of the summit crater at a depth of 0.2 km [0.1 mi]. This earthquake was the strongest event recorded beneath Great Sitkin Volcano since its period of unrest began in 2016. For comparison, the largest earthquake recorded beneath the volcano’s edifice since monitoring began in 1999 was ML 4.3. That event took place on May 28, 2002, and was located beneath the southeast flank of the volcano (Pesicek and others, 2008). \r\n\"The other notable earthquake activity at Great Sitkin Volcano in 2020 consisted of a cluster of seven earthquakes that occurred between January 31 and February 1. These seven events ranged from ML -0.6 to 0.27 and had depths ranging from 22.6 to 27.0 km [14.0 to 16.8 mi]. \r\n\"AVO noted no major changes or unusual activity at the summit crater and dome during 2020, although the degree of visible steaming decreased compared to the 2016-2019 period (Dixon and others, 2020; Cameron and others, 2023; Orr and others, 2023). Photographs taken by passing airplanes in March, shortly after the ML 3.47 earthquake of March 6, show small snow-free areas and minor steaming at the summit of the volcano. Satellite imagery of Great Sitkin Volcano acquired in June and July indicated weakly elevated surface temperatures.\"","StartYear":2020,"StartMonth":2,"StartDay":26,"StartTime":null,"StartQualifier":1,"StartQualifierUnit":"Months","EndYear":2020,"EndMonth":10,"EndDay":21,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Great Sitkin","ParentVolcano":"Great Sitkin","VolcanoID":"ak111","ParentVolcanoID":"ak111"},{"ID":4581,"Name":"Cleveland 2020/6","Description":"From Orr and others, 2024: \"Intermittent explosive eruptions have taken place [at Cleveland] every year since 2001. In 2020, Mount Cleveland had one confirmed explosion...\r\n\"[O]n June 2 at 06:31 UTC (June 1 at 21:31 HADT), a small explosion triggered the infrasound alarm in Adak, Alaska, and was detected shortly thereafter on the infrasound array in the City of Dillingham, Alaska. A small ash cloud was observed shortly afterward in satellite imagery drifting southward at an altitude of ~22,000 ft (~6,700 m). This event was the first explosion detected at Mount Cleveland since January 2019 - a span of 17 months and the longest repose period at the volcano since its onset of eruptive activity in 2001. In response, the Aviation Color Code and Volcano Alert Level were elevated to ORANGE and WATCH on June 2 at 07:46 UTC (June 1 at 22:46 HADT).\r\n\"The explosion destroyed ~60 percent of the 2019 dome, excavated and widened the crater slightly, and sent pyroclastic and debris flows as far as ~3 km [1.9 mi] down the flanks of the volcano. Hot debris landing on snow may have triggered some of these flows by melting and remobilizing mixtures of debris and snow. Satellite imagery acquired after the explosion also showed a trace ash deposit extending southward from the summit, discoloring the snow on the volcano’s flanks. Aerial photographs taken on June 3 showed that impact craters from ballistically ejected bombs and blocks dotted the snow, and satellite imagery acquired later showed that the ejecta reached as far as 1,400 m [4,600 ft] from the summit crater.\r\n\"Activity at Mount Cleveland diminished after the June 2 explosion. A weak steam plume dissipated after a few days, and no conspicuous degassing or definitive elevated surface temperatures were observed in satellite imagery thereafter through the rest of the year. Because of the lack of activity, the Aviation Color Code and Volcano Alert Level were downgraded to YELLOW and ADVISORY on June 17, then to UNASSIGNED on September 3, where the volcano stayed for the rest of the year.\"","StartYear":2020,"StartMonth":6,"StartDay":1,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2020,"EndMonth":6,"EndDay":1,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Cleveland","ParentVolcano":"Cleveland","VolcanoID":"ak52","ParentVolcanoID":"ak52"},{"ID":4591,"Name":"Makushin 2020/6","Description":"From Orr and others, 2024: \"Seismic activity near Makushin Volcano increased beginning in the summer of 2020. An earthquake swarm kicked off on June 15 at 21:16 UTC (13:16 AKDT) with an earthquake of local magnitude (ML) 4.2 that was located ~12 km [7.5 mi] east-southeast of the volcano. This event was followed by hundreds of aftershocks in the same general area with several of ML 3–4, including a ML 4.1 earthquake on June 16 at 00:34 UTC (June 15 at 16:34 AKDT). The two ML 4 earthquakes and many of their aftershocks were felt strongly by residents of the City of Unalaska. The earthquake depths during this period ranged from 5 to 14 km. \r\nElevated seismicity near the volcano continued for the remainder of 2020, although the events gradually decreased in frequency over time. No other signs of unrest or surface deformation were observed at Makushin Volcano in remote sensing data, gas measurements, GNSS data, InSAR data, or webcam images. However, several deep long-period (LP) earthquakes (depths greater than 9 km [5.6 mi]) were recorded beneath the volcano’s summit prior to and during the June swarm. These LP events may represent magma movement in the lower crust, although such earthquakes are not unusual for Makushin Volcano. \r\n\"At the time of the swarm, AVO was uncertain whether the earthquake sources were related to tectonic or volcanic stresses. Therefore, on June 16, a seismic watch schedule was implemented, and the Aviation Color Code and Volcano Alert Level were raised to YELLOW and ADVISORY. On September 8, after seismic activity had returned to background levels and no other signs of volcanic unrest were observed, the Aviation Color Code and Volcano Alert Level were lowered back to GREEN and NORMAL. \r\n\"By analyzing the fault plane solutions of the earthquakes in the swarm, Lanza and others (2022) found that many of the larger earthquakes had P-axes oriented consistently with the regional maximum compression, but most of the smaller earthquakes had P-axes perpendicular to the regional maximum compression. On the basis of these findings, they concluded that the triggering mechanism of the earthquakes was most likely a combination of stresses from tectonic and magmatic sources along existing fault lines.\"","StartYear":2020,"StartMonth":6,"StartDay":15,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2020,"EndMonth":9,"EndDay":8,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Makushin","ParentVolcano":"Makushin","VolcanoID":"ak188","ParentVolcanoID":"ak188"},{"ID":4601,"Name":"Veniaminof 2020/6","Description":"From Orr and others, 2024: \"Mount Veniaminof did not erupt in 2020, but it did experience a period of elevated seismicity. Beginning on June 14, 2020, this seismicity was characterized by brief periods of continuous tremor (each lasting ~30 seconds to several minutes) and occasional earthquakes. Although no other signs of unrest were observed, this departure from the volcano’s background seismic activity prompted AVO to increase its Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY on June 18. The seismicity changed little until early August, when the level of tremor began to gradually decline. The decrease in seismic activity and the lack of evidence for surface change (no increased temperatures or gas emissions) indicated that activity at Mount Veniaminof had returned to background levels. As a result of these observations, AVO decreased the Aviation Color Code and Volcano Alert Level to GREEN and NORMAL on August 20.\"","StartYear":2020,"StartMonth":6,"StartDay":16,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2020,"EndMonth":8,"EndDay":20,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Veniaminof","ParentVolcano":"Veniaminof","VolcanoID":"ak301","ParentVolcanoID":"ak301"},{"ID":4863,"Name":"Novarupta ash resuspension 2020","Description":"From Orr and others, 2024: \"On September 14 (AKDT), strong winds entrained and resuspended ash from the Katmai region, carrying it northwestward at an altitude of ~4,000 ft (~1,200 m). Strong winds again picked up ash on October 31 (AKDT), carrying it southward at an altitude of ~5,000 ft (~1,500 m), as well as on November 2 (AKDT), carrying the ash southeastward at an altitude of ~5,000 ft (~1,500 m). During each resuspension event, the National Weather Service Alaska Aviation Weather Unit issued a significant meteorological weather advisory for aviators and AVO issued an information statement. The Aviation Color Code and Volcano Alert Level remained GREEN and NORMAL for Mount Katmai during 2020.\"","StartYear":2020,"StartMonth":9,"StartDay":14,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2020,"EndMonth":11,"EndDay":2,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Novarupta","ParentVolcano":"Novarupta","VolcanoID":"ak203","ParentVolcanoID":"ak203"},{"ID":4631,"Name":"Korovin unrest 2020/10","Description":"From Orr and others, 2024: \"The first indication of unrest at Atka volcanic complex in 2020 was a small increase in seismic activity. This activity started in early June and culminated with episodic tremor on June 11-12. The amplitude of the tremor pulses, which each lasted 10-40 minutes, increased slowly and peaked on June 12 at ~13:50 UTC (~04:50 HADT). The tremor then subsided to background levels for the next several months. \r\n\"Beginning on October 15, the TROPOMI satellite instrument made occasional SO2 detections at Atka volcanic complex. These SO2 detections were the first at the complex in 2020 and indicated elevated volcanic degassing. An additional two satellite SO2 detections were made during the next two weeks, which also coincided with an increase in the number of earthquakes located in the area. In response to this heightened level of activity, AVO elevated the Aviation Color Code and Volcano Alert Level to YELLOW and ADVISORY on October 28. No additional satellite SO2 detections were made in the following weeks, and seismicity declined in late November, indicating a return to background activity. AVO subsequently lowered the Aviation Color Code and Volcano Alert Level back to GREEN and NORMAL on December 3.\"","StartYear":2020,"StartMonth":10,"StartDay":15,"StartTime":null,"StartQualifier":null,"StartQualifierUnit":null,"EndYear":2020,"EndMonth":12,"EndDay":3,"EndTime":null,"EndQualifier":null,"EndQualifierUnit":null,"Volcano":"Korovin","ParentVolcano":"Atka volcanic complex","VolcanoID":"ak171","ParentVolcanoID":"ak17"}]