Bogoslof

Photo of this volcano
  • United States
  • Alaska
  • Submarine
  • 1992 CE
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 53.93°N
  • 168.03°W

  • 150 m
    492 ft

  • 311300
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

Most Recent Weekly Report: 12 April-18 April 2017 Citation IconCite this Report


Increased seismicity at Bogoslof was recorded by stations on nearby islands starting around 1501 on 15 April, prompting AVO to raise the Aviation Color Code to Orange and the Volcano Alert Level to Watch. The seismic activity subsided a few hours later; there was no evidence of renewed eruptive activity from infrasound, lightning, or satellite data during 15-18 April.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


Most Recent Bulletin Report: July 1992 (BGVN 17:07) Citation IconCite this Report


New lava dome enlarges island

A large new lava dome grew on the N side of Bogoslof Island (figure 1) during the steam-and-ash eruption reported in 17:6. The eruption apparently began about 6 July, and the last reports of activity were received on 24 July.

Figure (see Caption) Figure 1. Sketch map of Bogoslof Island, showing the 1992 dome and new flat land just offshore (labeled "rocks"). Pre-1992 features are drawn from a 1982 pocket-transit survey by John Reeder, which had shown substantial erosion of the soft 1926-27 pyroclastic deposits since USGS mapping in 1947 (Byers, 1959). Courtesy of John Reeder.

A plume was first visible on satellite imagery at about 1500 on 6 July, rising to an estimated 3 km altitude. Previous small plumes, if any, would have been obscured by clouds at about 6 km altitude that had remained over the area for the previous few days. Just after 1700 on 6 July, Thomas Madsen (Aleutian Air) saw a continuously rising steam column that disappeared into low clouds at 350 m altitude. From his vantage point 30 km SSE, the column appeared to be emerging from the sea just beyond the island. No eruptive activity had been evident during his previous flight two days earlier. At about 1800, Joe May and David Alborn (MarkAir) saw a white plume reaching at least 1.8 km altitude. During the late afternoon of 7 July, a commercial fisherman saw a rocky new island, with steam and some ash emerging from its summit, between Bogoslof Island and Fire Island (the 1883 dome). A fracture extended from the new island's summit to the sea, from where steam was also rising. No eruptive activity had been evident when the fisherman passed Bogoslof early 6 July.

Only intermittent small plumes appeared on satellite imagery through 13 July. However, plumes were continuous for the next two days, reaching a maximum altitude, on 14 July, of 5.5 km. The largest plume, at 1140 on 15 July, extended ~100 km ESE over neighboring Unalaska Island at 3-3.5 km altitude. At 1755 that day, May and Alborn saw a fairly dark, continuous, steam-and-ash plume that reached about 3.5 km elevation. Satellite images again showed only intermittent plumes 16-17 July, and none since then. Additional pilot observations included a rapidly rising mushroom-shaped cloud with a black stem, reaching at least 4.5 km above sea level on 17 July at 1623 (Wyman Owens, Peninsula Airways). On 20 July at 1830 Joseph Maricelli (Northwest Airlines) saw a gray plume rising from Bogoslof, with a very pale top that may have reached 8 km altitude. A gray cloud was still rising to 4.5 km when Randy Lovett and Tom Peebles (MarkAir) passed at 2056.

Photographs taken from a boat by Larry Shaishnikoff on 21 July, and video footage from a U.S. Coast Guard C-130 aircraft on 24 July, show a profusely steaming new lava dome at the N tip of the main island. Steam with some ash was emerging from most of the dome's surface during Shaishnikoff's visit. Incandescent lava could be seen within large crags over most of the dome, but was brightest on the upper NW and SE flanks. Estimates of its size from the video footage (AVO) and photographs (John Reeder) were similar, at ~80-90 m high and roughly 300-400 m across. It has a steep-sided central spire surrounded by a blocky, more gently sloping debris apron, and is adjacent to the remnant of the 1927 dome. Rock color and surface texture looked very similar to those of the 1927 dome in the Shaishnikoff photos. Approximately horizontal new land ("rocks" on figure 1) extended slightly above sea level just NNE of the dome. No steaming was occurring from these rocks, which may have been uplifted sea floor. Dall porpoises, numerous birds, and some Steller sea lions near Fire Island, several hundred meters from the new dome, did not appear to have been affected by the activity.

Pilot reports of steaming and possible ash emission continued through 24 July, after which occasional pilot observations indicated no further significant activity.

No ashfall has been reported at the two nearest towns, Dutch Harbor/Unalaska (100 km E of Bogoslof) and Nikolski (Umnak I., 120 km SW). The principal hazards from Bogoslof's eruptions are to aircraft in the Aleutian Islands and on Trans-Pacific international routes across the Bering Sea. No aircraft incidents have been reported. A SIGMET issued 20 July was cancelled the next day. No seismometers are maintained near the island.

The volcano's subaerial portion consists of fragmental deposits, agglomerate, lava spires, dome remnants, and beach sediments, all of historical age (Byers, 1959). All sampled rocks are high-potassium andesites and basalts (Arculus et al., 1977). The island is remote and uninhabited, but houses a large sea-lion rookery. The island's low elevation and frequent explosive activity since the first historical eruption in 1796 have resulted in rapid, well-documented morphologic changes over the past 200 years. Particularly vigorous eruptions occurred in 1883, 1907 (both of which deposited small amounts of ash on Dutch Harbor), and 1926-27. These eruptions were characterized by sporadic, violent explosions, with lava flows and dome-building continuing for several months (Jaggar, 1930). Three kilometers of muddy water encountered by a ship near the island in September 1951 may have been from a submarine eruption.

References. Arculus, R., Delong, S., Kay, R.W., Brooks, C., and Sun, S., 1977, The Alkalic Rock Suite of Bogoslof Island, Eastern Aleutian Arc, Alaska: Journal of Geology, v. 85, p. 177-186.

Byers, F.M., 1959, Geology of Umnak and Bogoslof Islands, Alaska: USGS Bulletin 1028-L.

Jaggar, T., 1930, Recent Activity of Bogoslof Volcano: The Volcano Letter, no. 275, p. 1-3.

Information Contacts: AVO; J. Reeder, ADGGS.

Weekly Reports - Index


2017: January | February | March | April
2016: December


12 April-18 April 2017 Citation IconCite this Report


Increased seismicity at Bogoslof was recorded by stations on nearby islands starting around 1501 on 15 April, prompting AVO to raise the Aviation Color Code to Orange and the Volcano Alert Level to Watch. The seismic activity subsided a few hours later; there was no evidence of renewed eruptive activity from infrasound, lightning, or satellite data during 15-18 April.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


5 April-11 April 2017 Citation IconCite this Report


On 5 April AVO reported that the Aviation Color Code for Bogoslof was lowered to Yellow and the Volcano Alert Level was lowered to Advisory based on the absence of detected activity at the volcano for the past three weeks; the last large explosion occurred on 8 March. No significant volcanic activity was detected in seismic, infrasound, or satellite data during 6-11 April.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


29 March-4 April 2017 Citation IconCite this Report


AVO reported that no significant volcanic activity at Bogoslof was detected in seismic or infrasound data during 29 March-4 April, and satellite views were often obscured by clouds or showed nothing noteworthy. Weakly elevated surface temperatures were identified in satellite images during 28-29 March. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Warning.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


22 March-28 March 2017 Citation IconCite this Report


AVO reported that no significant volcanic activity at Bogoslof was detected in seismic or infrasound data during 22-28 March, and satellite views were often obscured by clouds or showed nothing noteworthy. Weakly elevated surface temperatures were identified in satellite images during 21-23 March. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Warning.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


15 March-21 March 2017 Citation IconCite this Report


AVO reported that no significant volcanic activity at Bogoslof was detected in seismic or infrasound data during 15-21 March, and satellite views were either obscured by clouds or showed nothing noteworthy. Slightly elevated surface temperatures were identified in satellite images during 16-17 and 20-21 March. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Warning.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


8 March-14 March 2017 Citation IconCite this Report


AVO reported that an explosive event at Bogoslof began at about 2236 on 7 March, indicated in seismic, lightning, and infrasound data, and lasted about three hours. Though ash was not immediately visible in satellite data, AVO raised the Aviation Color Code (ACC) to Red and the Volcano Alert Level (VAL) to Warning. Later, satellite images showed a large ash cloud rising to an altitude of 10.7 km (35,000 ft) a.s.l. and drifting E. This event was the first detected eruptive activity since 19 February, and more than 1,000 lightning strokes related to the volcanic eruption cloud were detected during this event, by far the highest number observed to date. In addition the seismic levels were among the highest detected since the beginning of the eruption. Satellite images from 8 March showed that the W part of the island had grown significantly. The ACC was lowered to Orange and the VAL was lowered to Watch on 9 March.

Two earthquakes swarms were detected during 9-11 March; the first began at 1750 on 9 March and ended at 1400 on 10 March, and the second was detected from 1900 on 10 March to 0500 on 11 March. Mildly elevated surface temperatures were identified in satellite data during 10-11 March. A third swarm began at 0500 on 12 March. A short-duration event, from 1131 to 1143 on 13 March, produced a small ash cloud that rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted SSW. AVO noted that after the event, the level of seismic activity declined and the repeating earthquakes, detected for much of the previous several days, stopped. Weakly elevated surface temperatures were observed in two satellite images from 13 March. A photograph taken by a pilot showed a low-level, billowy steam plume rising from the general area of the intra-island lake.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


1 March-7 March 2017 Citation IconCite this Report


AVO reported that no significant volcanic activity at Bogoslof had been detected in seismic, infrasound, or sometimes cloudy satellite data during 1-7 March. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Warning.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


22 February-28 February 2017 Citation IconCite this Report


AVO reported that no significant volcanic activity at Bogoslof had been detected in seismic, infrasound, or mostly cloudy satellite data during 22-28 February. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Warning.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


15 February-21 February 2017 Citation IconCite this Report


AVO reported that during 15-16 February cloud cover prevented satellite views of Bogoslof; no other data indicated eruptive activity. At 0955 on 17 February seismic data indicated the beginning of an explosive event, prompting AVO to raise the Aviation Color Code (ACC) to Red and the Volcano Alert Level (VAL) to Warning. Individual pulses of seismicity was recorded until 1140, and then afterwards seismicity was low. Satellite images and pilot observations indicated that an ash plume rose to an altitude of 11.6 km (38,000 ft) a.s.l. The event was also verified by infrasound and lightning data. Another short-lived explosive event began at 1546, detected in infrasound and seismic data. A volcanic cloud identified in satellite images rose as high as 7.6 km (25,000 ft) a.s.l.

An explosion at 0450 on 18 February was detected in seismic, infrasound, and lightning data. The seismic data suggested that ash emissions lasted several minutes, and then seismicity decreased. A preliminary evaluation of satellite data indicated that a cloud rose at least as high as 7.6 km (25,000 ft) a.s.l.; the cloud drifted SW. On 19 February the ACC was lowered to Orange and the VAL was lowered to Watch. Later that day seismic and infrasound data recorded a series of short-lived explosive pulses during 1708-1745. The ACC was raised to Red and the VAL was raised to Warning. A plume identified in satellite images rose as high as 7.6 km (25,000 ft) a.s.l. and drifted 160 km SE over Unalaska Island. AVO geologists on the island described the cloud has having a white upper portion and a slightly darker lower portion. Storms in the region impacted data communications at AVO's facility in Dutch Harbor on 20 February, limiting AVO's ability to forecast and detect eruptions at Bogoslof.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


8 February-14 February 2017 Citation IconCite this Report


AVO reported that during 8-12 and 14 February cloud cover prevented satellite views of Bogoslof; no other data indicated eruptive activity. At 0724 on 13 February seismicity significantly increased, prompting AVO to raise the Aviation Color Code (ACC) to Red and the Volcano Alert Level (VAL) to Warning. Satellite images acquired through 0930 showed no ash emissions above the 3 km (10,000 ft) a.s.l. cloud deck, and no lightning was detected. AVO concluded that, despite the intensity of seismic activity, a significant ash emission was not produced during this event; the ACC was lowered to Orange and the VAL was lowered to Watch.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


1 February-7 February 2017 Citation IconCite this Report


AVO reported that no further emissions were detected at Bogoslof after an explosion at 0520 on 31 January; the Aviation Color Code (ACC) was lowered to Orange and the Volcano Alert Level (VAL) was lowered to Watch the next day. A burst of tremor lasting nine minutes was detected starting at 0457 on 3 February. A second burst, starting at 0533 and lasting 20 minutes, was also detected by infrasound instruments, indicating an explosion. No ash cloud was detected above the meteorological cloud deck in satellite data. An event that began at 1642 produced a small volcanic plume that drifted about 40 km N below an altitude of 7.6 km (25,000 ft) a.s.l. Seismic tremor significantly decreased later that evening. Weakly elevated surface temperatures were observed in two satellite images acquired on 5 February, possibly related to hot deposits from explosive activity the day before.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


25 January-31 January 2017 Citation IconCite this Report


AVO reported that no further emissions were detected at Bogoslof after an explosion at 0453 on 24 January; the Aviation Color Code (ACC) was lowered to Orange and the Volcano Alert Level (VAL) was lowered to Watch the next day. An hour-long seismic increase began at 0134 on 25 January though no evidence of eruptive activity was evident. Based on lightning and seismic data an explosive event began at 0650 on 26 January, and another burst of seismicity was recorded at 0706. The ACC was raised to Red and the VAL was raised to Warning. An ice-rich cloud, first identified in satellite data at 0700, likely contained ash, and rose as high as 9.8 km (32,000 ft) a.s.l. and drifted SE at lower altitudes, and NE at altitudes above about 6.1 km (20,000 ft) a.s.l. The ACC was lowered to Orange and the VAL was lowered to Watch later that day. Lightning and seismic data again indicated an explosive event at 0824 on 27 January, prompting AVO to raise the Aviation Color Code (ACC) to Red and the Volcano Alert Level (VAL) to Warning. An ice-rich cloud that likely contained ash rose to an altitude of 7.6 km (25,000 ft) a.s.l. and drifted E; seismicity related to ash emissions remained elevated for 48 minutes. The ACC was lowered to Orange and the VAL was lowered to Watch later that day.

Several short bursts of seismic activity were detected at 0520 and 0608 on 30 January. An infrasound signal accompanied the first event indicating an explosion; an eruption cloud was identified in satellite data at 0530, rising to an altitude of 6.1 km (20,000 ft) a.s.l. later that day AVO noted that bursts of explosive activity continued and intensified; more than 10 short-duration explosions were detected in seismic, infrasound, and lightning data. The Aviation Color Code (ACC) was raised to Red and the Volcano Alert Level (VAL) was raised to Warning. Ash plumes rose as high as 7.6 km (25,000 ft) a.s.l. and drifted 125 km SE. Trace amounts of ashfall and a sulfur odor were reported in Unalaska/Dutch Harbor (98 km E). By the next day the explosions had subsided or ended. Satellite images acquired on 31 January showed significant changes to the island. AVO stated that freshly erupted volcanic rock and ash had formed a barrier that separated the vent from the sea, suggesting that the change had resulted in the more ash-rich emissions occurring during 30-31 January.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


18 January-24 January 2017 Citation IconCite this Report


AVO reported that an explosive event at Bogoslof began at about 1320 on 18 January, generating an ash plume that rose at least to an altitude of 9.4 km (31,000 ft) a.s.l. and drifted NE. The dark (ash-rich) plume was identified in satellite images and observed by a pilot, and produced lightning strikes and infrasound signals detected by sensors in Sand Point and Dillingham. Analysis of a satellite image suggested the presence of very hot material (lava) at the surface immediately surrounding the vent, which was the first such observation since the beginning of the eruption. AVO raised the Aviation Color Code (ACC) to Red and the Volcano Alert Level (VAL) to Warning. A second lower-altitude cloud was visible in satellite images around 1400, likely corresponding with an increase in seismic tremor that occurred from 1340-1355. The ACC was lowered to Orange and the VAL was lowered to Watch the next day.

Another explosion was detected at 1317 on 20 January, following an approximately 30-minute-long increase in seismic activity, based on seismic data and lightning detected from the World Wide Lightning Location Network. Pilots observed an ash plume rising to an altitude of 11 km (36,000 ft) a.s.l. and drifting SE. Satellite images indicated an ice-rich plume and lava present at the vent. The ACC was raised to Red and the VAL was raised to Warning, but were again lowered one level to Orange and Watch, respectively, the next day. Several lightning strikes north of Bogoslof indicated that an explosive event began at 1409 on 22 January. An ash plume identified in satellite images rose to an altitude of 9.1 km (30,000 ft) a.s.l. The ACC was raised to Red and the VAL was raised to Warning, and again lowered one level the next day. Following a period of increasing seismicity, an explosive event began at 0453 on 24 January, as indicated in seismic data and lightning detection, prompting AVO to raise the ACC to Red and the VAL to Warning. Seven minutes later an ice-rich plume which likely contained ash rose too altitudes of 7.6-10.7 km (25,000-35,000 ft) a.s.l. and drifted E.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


11 January-17 January 2017 Citation IconCite this Report


AVO reported that photos taken by a pilot on 10 January showed Bogoslof covered with dark gray ash, and a roughly 300-m-diameter submarine explosion crater on the E side of the island. Unrest continued during 11-17 January. Two short-lived explosions (five to six minutes long) were seismically detected at 1123 and 1230 on 12 January and observed by pilots. The estimated altitudes of the first and second plumes were 5.5 and 4.4 km (18,000 and 14,500 ft) a.s.l., respectively. Seismicity again increased at 2126 on 14 January and remained elevated. Six explosive events were detected between 2216 on 14 January and 0350 on 15 January. No volcanic clouds were identified in satellite data, although one lightning strike was recorded at 2232 on 14 January. Increased seismicity on 17 January indicated minor explosive activity; steam plumes with minor amounts of ash rose no higher than 4.6 km (15,000 ft) a.s.l. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


4 January-10 January 2017 Citation IconCite this Report


AVO reported that a five-minute-long seismic signal detected by sensors on islands near Bogoslof began at 2118 on 3 January along with a series of lightning strikes identified by the World Wide Lightning Location Network. An ash cloud identified in satellite data rose as high as 10 km (33,000 ft) a.s.l. and drifted N. AVO raised the Aviation Color Code (ACC) to Red and the Volcano Alert Level (VAL) to Warning. No other indications of activity were noted for the next few days, the ACC and the VAL were lowered to Orange and Watch, respectively, on 5 January. Later that day, at 1324, seismicity again escalated, and lightning strikes indicated another significant and short-lived (five minutes) explosion. The ash plume was visible on satellite images and observed by pilots, and had risen to an estimated altitude of 10.7 km (35,000 ft) a.s.l., detached, and drifted NNW. The ACC was raised to Red and the VAL was raised to Warning, but were again lowered one level the next day. Seismic and infrasound data from neighboring islands indicated another explosive event, beginning at 2230 on 8 January. Seismic data suggested two strong pulses, during 2233-2234 and at 2256, consistent with two distinct volcanic clouds observed in satellite images. The second cloud was larger, rising to an altitude of 10.7 km (35,000 ft) a.s.l. and drifting NW. The ACC was raised to Red and the VAL was raised to Warning, but were again lowered one level to Orange and Watch, respectively, the next day.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


28 December-3 January 2017 Citation IconCite this Report


On 27 December AVO noted that since there was no indication of elevated seismicity at Bogoslof during the previous day the Aviation Color Code (ACC) was lowered to Orange and the Volcano Alert Level (VAL) was lowered to Orange. AVO noted that there is no ground-based volcano monitoring equipment on Bogoslof; activity is monitored by satellite images, information from the Worldwide Lightning Location Network pertaining to volcanic-cloud lightning, and data from seismic and infrasound instruments on other islands.

An increase of volcanic tremor started to be detected at 1755 on 28 December with the largest burst, recorded at 1807 and lasting 50 minutes. Inclement weather prevented satellite confirmation of accompanying emissions. The report noted that this type of seismic activity had accompanied each of the previous explosions at Bogoslof since the eruption began last week, prompting AVO to issue a Volcano Activity Notice (VAN) and Volcano Observatory Notice for Aviation (VONA) in case there was an ash plume released.

Another increase in seismicity began at 1900 on 29 December and progressed, merging into a continuous tremor sequence indicative of a possible ash-producing eruption. At 2345 a 30-minute-long, ash-producing event began, with an ash plume possibly rising as high as 6.1 km (20,000 ft) a.s.l. that drifted NE. The ACC and VAL were raised to Red and Warning, respectively. A 45-minute-long explosive event began at 2230 on 30 December, indicated by seismic data and lightning strikes. Meteorological cloud cover prevented satellite views. No further explosions were detected afterward, so on 1 January 2017 the ACC was lowered to Orange and the VAL was lowered to Watch. Increased seismicity detected at 1353 on 2 January and lasting about 10 minutes likely indicated a relatively minor explosion; meteorological cloud cover prevented visual observations.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


21 December-27 December 2016 Citation IconCite this Report


AVO reported that the explosive eruption at Bogoslof, which was reported by several pilots around 1530 on 20 December and produced an ash plume that rose to 10.3 km (34,000 ft) a.s.l., lasted about 30 minutes. The ash plume detached and dispersed S. AVO had raised the Aviation Color Code (ACC) to Red and the Volcano Alert Level (VAL) to Warning, but since no further activity was detected or observed the ACC was lowered to Orange and the VAL was lowered to Watch. On 21 December periods of discrete earthquakes and continuous seismic tremor were recorded by instruments on nearby volcanoes. At 1610 an explosive eruption detected in satellite data and by seismic instruments on nearby islands again lasted about 30 minutes. An ash plume rose to an altitude of 10.7 km (35,000 ft) a.s.l. and drifted N. The ACC and VAL were raised to Red and Warning, respectively. Seismicity declined rapidly afterward and remained low; the ACC was lowered to Orange and the VAL was lowered to Watch. Strong continuous seismic activity started abruptly at about 1340 on 22 December.

AVO noted that the eruption had dramatically changed the island. Satellite images showed that a small new island had formed just offshore of the NE end of the main island, the previous shore and much of the NE side of Bogoslof Island adjacent to the new island had been mostly removed (and was likely the site of the new, underwater vent), and deposition of material had occurred on the W side of the island.

An explosion occurred at 0930 on 23 December. A Coast Guard ship in the vicinity reported ash emissions, lightning, and ejected lava and fragmented material. The ash plume rose to an altitude below 9.1 km (30,000 ft) a.s.l. Coast Guard observers noted that ash emission subsided around 1037. The ACC/VAL were raised to Red/Warning. On 24 December seismic unrest was periodically detected by nearby island networks, but levels were generally low. The ACC was lowered to Orange and the VAL was lowered to Watch. A period of tremor detected in the evening on 25 December may have been associated with a minor, low-level ash emission (below 3 km or 10,000 ft a.s.l.); several lightning strikes in the area were recorded. Lightning strikes, seismic data, and satellite images indicated a continuing eruption that began at 1405 on 26 December. An ash plume rose to an altitude of 9.1 km (30,000 ft) a.s.l. and drifted WSW. The ACC/VAL were again raised to Red/Warning.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


14 December-20 December 2016 Citation IconCite this Report


AVO reported that a short-lived explosive eruption at Bogoslof, observed and reported by several pilots around 1600 on 20 December, produced an ash plume that rose to 10.3 km (34,000 ft) a.s.l. A subsequent pilot report made 50 minutes later indicated that activity had decreased. Satellite data showed a discrete, short-lived explosion just prior to 1600, and a detached plume that drifted S. AVO raised the Aviation Color Code to Red and the Volcano Alert Level to Warning.

Source: US Geological Survey Alaska Volcano Observatory (AVO)


Bulletin Reports - Index


Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

06/1992 (BGVN 17:06) Steam and ash emission

07/1992 (BGVN 17:07) New lava dome enlarges island




Information is preliminary and subject to change. All times are local (unless otherwise noted)


June 1992 (BGVN 17:06) Citation IconCite this Report


Steam and ash emission

A eruption . . . had begun by 6 July, when airplane pilots first reported steam and ash rising through low clouds. Similar activity was seen through the week, when satellite images revealed repeated plumes from Bogoslof. Pilots reported a cloud to ~3 km altitude on 14 July at 1815. Satellite images showed the plume extending roughly 100 km SE, to the S side of Unalaska Island. An image from 16 July at 1140 showed another plume extending ~100 km E to Unalaska. That day, a pilot saw a white plume rising to ~4 km altitude. An episode of vigorous steam and ash ejection began on 20 July at about 1700, and material had reached nearly 8 km asl by 1725, drifting NNE. A dark gray cloud that was ~15 km wide at 3 km altitude was moving NW from the volcano several hours later. Poor weather prevented subsequent observations, but satellite images showed no volcanic plumes rising above weather-cloud tops at ~6 km elevation. There have been no reports of ashfall. Cloudy weather has prevented direct observation of the island . . . .

Information Contacts: AVO; SAB.


July 1992 (BGVN 17:07) Citation IconCite this Report


New lava dome enlarges island

A large new lava dome grew on the N side of Bogoslof Island (figure 1) during the steam-and-ash eruption reported in 17:6. The eruption apparently began about 6 July, and the last reports of activity were received on 24 July.

Figure (see Caption) Figure 1. Sketch map of Bogoslof Island, showing the 1992 dome and new flat land just offshore (labeled "rocks"). Pre-1992 features are drawn from a 1982 pocket-transit survey by John Reeder, which had shown substantial erosion of the soft 1926-27 pyroclastic deposits since USGS mapping in 1947 (Byers, 1959). Courtesy of John Reeder.

A plume was first visible on satellite imagery at about 1500 on 6 July, rising to an estimated 3 km altitude. Previous small plumes, if any, would have been obscured by clouds at about 6 km altitude that had remained over the area for the previous few days. Just after 1700 on 6 July, Thomas Madsen (Aleutian Air) saw a continuously rising steam column that disappeared into low clouds at 350 m altitude. From his vantage point 30 km SSE, the column appeared to be emerging from the sea just beyond the island. No eruptive activity had been evident during his previous flight two days earlier. At about 1800, Joe May and David Alborn (MarkAir) saw a white plume reaching at least 1.8 km altitude. During the late afternoon of 7 July, a commercial fisherman saw a rocky new island, with steam and some ash emerging from its summit, between Bogoslof Island and Fire Island (the 1883 dome). A fracture extended from the new island's summit to the sea, from where steam was also rising. No eruptive activity had been evident when the fisherman passed Bogoslof early 6 July.

Only intermittent small plumes appeared on satellite imagery through 13 July. However, plumes were continuous for the next two days, reaching a maximum altitude, on 14 July, of 5.5 km. The largest plume, at 1140 on 15 July, extended ~100 km ESE over neighboring Unalaska Island at 3-3.5 km altitude. At 1755 that day, May and Alborn saw a fairly dark, continuous, steam-and-ash plume that reached about 3.5 km elevation. Satellite images again showed only intermittent plumes 16-17 July, and none since then. Additional pilot observations included a rapidly rising mushroom-shaped cloud with a black stem, reaching at least 4.5 km above sea level on 17 July at 1623 (Wyman Owens, Peninsula Airways). On 20 July at 1830 Joseph Maricelli (Northwest Airlines) saw a gray plume rising from Bogoslof, with a very pale top that may have reached 8 km altitude. A gray cloud was still rising to 4.5 km when Randy Lovett and Tom Peebles (MarkAir) passed at 2056.

Photographs taken from a boat by Larry Shaishnikoff on 21 July, and video footage from a U.S. Coast Guard C-130 aircraft on 24 July, show a profusely steaming new lava dome at the N tip of the main island. Steam with some ash was emerging from most of the dome's surface during Shaishnikoff's visit. Incandescent lava could be seen within large crags over most of the dome, but was brightest on the upper NW and SE flanks. Estimates of its size from the video footage (AVO) and photographs (John Reeder) were similar, at ~80-90 m high and roughly 300-400 m across. It has a steep-sided central spire surrounded by a blocky, more gently sloping debris apron, and is adjacent to the remnant of the 1927 dome. Rock color and surface texture looked very similar to those of the 1927 dome in the Shaishnikoff photos. Approximately horizontal new land ("rocks" on figure 1) extended slightly above sea level just NNE of the dome. No steaming was occurring from these rocks, which may have been uplifted sea floor. Dall porpoises, numerous birds, and some Steller sea lions near Fire Island, several hundred meters from the new dome, did not appear to have been affected by the activity.

Pilot reports of steaming and possible ash emission continued through 24 July, after which occasional pilot observations indicated no further significant activity.

No ashfall has been reported at the two nearest towns, Dutch Harbor/Unalaska (100 km E of Bogoslof) and Nikolski (Umnak I., 120 km SW). The principal hazards from Bogoslof's eruptions are to aircraft in the Aleutian Islands and on Trans-Pacific international routes across the Bering Sea. No aircraft incidents have been reported. A SIGMET issued 20 July was cancelled the next day. No seismometers are maintained near the island.

The volcano's subaerial portion consists of fragmental deposits, agglomerate, lava spires, dome remnants, and beach sediments, all of historical age (Byers, 1959). All sampled rocks are high-potassium andesites and basalts (Arculus et al., 1977). The island is remote and uninhabited, but houses a large sea-lion rookery. The island's low elevation and frequent explosive activity since the first historical eruption in 1796 have resulted in rapid, well-documented morphologic changes over the past 200 years. Particularly vigorous eruptions occurred in 1883, 1907 (both of which deposited small amounts of ash on Dutch Harbor), and 1926-27. These eruptions were characterized by sporadic, violent explosions, with lava flows and dome-building continuing for several months (Jaggar, 1930). Three kilometers of muddy water encountered by a ship near the island in September 1951 may have been from a submarine eruption.

References. Arculus, R., Delong, S., Kay, R.W., Brooks, C., and Sun, S., 1977, The Alkalic Rock Suite of Bogoslof Island, Eastern Aleutian Arc, Alaska: Journal of Geology, v. 85, p. 177-186.

Byers, F.M., 1959, Geology of Umnak and Bogoslof Islands, Alaska: USGS Bulletin 1028-L.

Jaggar, T., 1930, Recent Activity of Bogoslof Volcano: The Volcano Letter, no. 275, p. 1-3.

Information Contacts: AVO; J. Reeder, ADGGS.

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Eruptive History


There is data available for 11 Holocene eruptive periods.


Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1992 Jul 6 1992 Jul 24 Confirmed 3 Historical Observations North tip of island (NE of 1927 dome)
[ 1951 Sep 21 ] [ Unknown ] Uncertain 0  
1931 Oct 31 Unknown Confirmed 1 Historical Observations 1926-1927 dome
1926 Jul 1928 Confirmed 2 Historical Observations Between New and Old Bogoslof
[ 1913 Jul ] [ Unknown ] Uncertain     Tahoma Peak
1909 Sep 1910 Sep 19 Confirmed 2 Historical Observations Tahoma Peak
[ 1908 Jan 15 ± 45 days ] [ Unknown ] Uncertain     Metcalf Peak
1906 Mar 1 ± 30 days 1907 Sep 1 Confirmed 3 Historical Observations Metcalf Peak, McCullough Peak
1883 Sep 27 (in or before) 1895 ± 2 years Confirmed 3 Historical Observations New Bogoslof (Grewingk)
1806 1823 Confirmed 2 Historical Observations Old Bogoslof (Castle Rock)
1796 May 1804 Confirmed 3 Historical Observations Old Bogoslof (Castle Rock)

Deformation History


There is no Deformation History data available for Bogoslof.

Emission History


There is no Emissions History data available for Bogoslof.

Photo Gallery


Steam clouds produced by degassing of a growing lava dome rise from the northern tip of Bogoslof Island on July 21, 1992. The 1992 eruption was first observed on July 6, when pilots saw steam and ash rising from low clouds above the volcano. On July 20 an ash column rose to 8 km. A new lava dome grew to 100-m height by the time the eruption ended in late July. The low, 1927 basaltic lava dome forms the dark mass to the right with the pinnacle of Castle Rock behind it.

Photo by Larry Shaishnikoff, 1992 (courtesy of John Reeder, Alaska Div. Geology & Geophysical Surveys).
See title for photo information.
Lava dome remnants from three historical eruptions can be seen in this NW-looking aerial view of Bogoslof Island in the Aleutians. The pinnacle on the left is Castle Rock, also referred to as Old Bogoslof, a remnant of a 1796 lava dome. The circular, flat-topped area to its right is a remnant of a 1927 lava dome. The most recent eruption of Bososlof, in 1992, produced the light-colored conical lava dome forming the tip of the island at upper right. Frequent eruptions and vigorous wave erosion have greatly modified the island in historical time.

Photo by Chris Nye, 1994 (Alaska Division of Geological & Geophysical Surveys).
See title for photo information.
An aerial view shows the 1992 lava dome of Bogoslof Island, the summit of a largely submarine stratovolcano located in the Bering Sea 50 km behind the main Aleutian arc. The 1992 lava dome grew to a height of 100 m in July at the northern tip of Bogoslof Island. The island is about 1.5 x 0.6 km wide, and due to its frequent eruptive activity and energetic wave action, has changed shape dramatically since first mapped in the late 1700's.

Photo by Tom Miller, 1994 (Alaska Volcano Observatory, U.S. Geological Survey).
See title for photo information.
Bogoslof Island is the summit of a largely submarine stratovolcano located in the Bering Sea 50 km behind the main Aleutian arc. The island is about 1.5 x 0.6 km wide, and due to its frequent eruptive activity and energetic wave action, has changed shape dramatically since first mapped in the late 1700's. The conical, rubbly lava dome and offshore spire at the northern tip of the island (bottom center) were formed in 1992. The circular, flat area at the right is a remnant of the 1927 lava dome, and the steep pinnacle is Castle Rock, a 1796 dome remnant.

Photo by Terry Keith, 1994 (Alaska Volcano Observatory, U.S. Geological Survey).
See title for photo information.
Lava dome remnants from four historical eruptions can be seen in this NW-looking aerial view of Bogoslof Island in the Aleutians. The pinnacle on the left is Castle Rock, also referred to as Old Bogoslof, a remnant of a 1796 lava dome. The circular, flat-topped area to its right is a remnant of a 1927 lava dome. The most recent eruption of Bososlof, in 1992, produced the light-colored conical lava dome forming the tip of the island at upper right part of the island. The island at the upper right was formed in 1883.

Photo by John Sease, 1998 (NMS/NOAA).
See title for photo information.

Smithsonian Sample Collections Database


The following 11 samples associated with this volcano can be found in the Smithsonian's NMNH Department of Mineral Sciences collections, and may be availble for research (contact the Rock and Ore Collections Manager). Catalog number links will open a window with more information.

Catalog Number Sample Description Lava Source Collection Date
NMNH 111123-315 Hornblende Andesite -- --
NMNH 111123-316 Hornblende Andesite -- --
NMNH 117642-1 Pumice -- --
NMNH 117642-2 Pumice -- --
NMNH 36855-1 Volcanic Ash -- --
NMNH 36855-2 Hornblende Andesite -- --
NMNH 37033 Hornblende Andesite -- --
NMNH 37034 Hornblende -- --
NMNH 37034-1 Volcanic Ash -- --
NMNH 37034-2 Volcanic Ash -- --
NMNH 37034-3 Andesite Volcanic Ash -- --

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