USGS Volcano Notice - DOI-USGS-AVO-2022-03-18T09:38:53-08:00

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, March 18, 2022, 11:47 AM AKDT (Friday, March 18, 2022, 19:47 UTC)

GREAT SITKIN VOLCANO (VNUM #311120)
52°4'35" N 176°6'39" W, Summit Elevation 5709 ft (1740 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Satellite images early in the past week showed that slow lava effusion continues at Great Sitkin. Two lava flow lobes, south and west of the summit crater, continue to grow in length. A steam plume from the active vent in the summit crater was also observed. Clouds obscured all images after March 15. The overall level of seismicity was very low.

Erupted lava has overtopped the summit crater rim and is flowing into small valleys on the south, west, and north flanks of the volcano. The terrain is steep in these areas, and blocks of lava could detach from the terminus of the flow lobes without warning and form small rock avalanches in these valleys. One such avalanche from the southern crater rim flow front was observed in satellite data from March 7, 2022. These avalanches may liberate ash and gas and could travel several hundred meters beyond the lava flows; they would be hazardous to anyone in those areas.

Great Sitkin is monitored by local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks.

Great Sitkin Volcano is a basaltic andesite volcano that occupies most of the northern half of Great Sitkin Island, a member of the Andreanof Islands group in the central Aleutian Islands. It is located 26 mi (43 km) east of the community of Adak. The volcano is a composite structure consisting of an older dissected volcano and a younger parasitic cone with a 3 km-diameter summit crater. A steep-sided lava dome, emplaced during the most recent significant eruption in 1974, occupies the center of the crater. That eruption produced at least one ash cloud that likely exceeded an altitude of 25,000 ft (7.6 km) above sea level. A poorly documented eruption occurred in 1945, also producing a lava dome that was partially destroyed in the 1974 eruption. Within the past 280 years a large explosive eruption produced pyroclastic flows that partially filled the Glacier Creek valley on the southwest flank.

PAVLOF VOLCANO (VNUM #312030)
55°25'2" N 161°53'37" W, Summit Elevation 8261 ft (2518 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

The eruption of Pavlof Volcano continued throughout the past week and was characterized by occasional small explosions early in the week and growth of a spatter cone from the east summit vent. No ash emissions were detected in clear webcam or satellite images. No explosions have been detected since March 14 but moderate seismic tremor and satellite detection of elevated surface temperatures were seen each day.

Periods of lava spatter and fountaining from the vent on the volcano’s upper east flank have been occurring since mid-November 2021. This activity has built a small cone and sent flows down the flank that melt the snow and ice and produce variable amounts of meltwater. The meltwater typically incorporates loose debris on the flank of the volcano and forms thin (less than 2 m thick) lahars. The lahar deposits extend down the east-southeast flank for several kilometers, not quite to the base of the volcano.

Previous eruptions of Pavlof indicate that the level of unrest can change quickly and the progression to more significant eruptive activity can occur with little or no warning.

Pavlof is monitored by local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks.

Pavlof Volcano is a snow- and ice-covered stratovolcano located on the southwestern end of the Alaska Peninsula about 592 mi (953 km) southwest of Anchorage. The volcano is about 4.4 mi (7 km) in diameter and currently has active vents on the north and east sides close to the summit. With over 40 historic eruptions, it is one of the most consistently active volcanoes in the Aleutian arc. Eruptive activity is generally characterized by sporadic Strombolian lava fountaining continuing for a several-month period. Ash plumes as high as 49,000 ft (15 km) above sea level have been generated by past eruptions of Pavlof, and during the March 2016 eruption, ash plumes as high as 40,000 ft (12.2 km) above sea level were generated and the ash was tracked in satellite data as distant as eastern Canada. The nearest community, King Cove, is located 30 mi (48 km) to the southwest of Pavlof.

SEMISOPOCHNOI VOLCANO (VNUM #311060)
51°55'44" N 179°35'52" E, Summit Elevation 2625 ft (800 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

The eruption at Semisopochnoi volcano continued during the last week. Small explosions were detected in seismic and infrasound data each day. Seismicity remains elevated, and mostly consisted of periods of seismic tremor. Clear satellite and webcam images showed continuous steaming and low-level ash emission from the north crater of Mount Cerberus.

Small explosions that produce minor ash deposits within the vicinity of the active north crater of Mount Cerberus, with ash clouds typically under 10,000 ft (3 km) above sea level, have characterized the recent activity and show no signs of abating.

Semisopochnoi is monitored by local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks.

Remote Semisopochnoi volcano occupies the largest, young volcanic island in the western Aleutians. The volcano is dominated by a 5-mile (8 km) diameter caldera that contains a small lake and several post-caldera cones and craters. The age of the caldera is not known with certainty but is likely early Holocene. Prior to 2018, the previous known historical eruption of Semisopochnoi occurred in 1987, probably from Sugarloaf Peak on the south coast of the island, but details are lacking. Another prominent, young post-caldera landform is Mount Cerberus, a three-peaked cone cluster in the southwest part of the caldera. The island is uninhabited and part of the Alaska Maritime National Wildlife Refuge. It is located 40 mi (65 km) northeast of Amchitka Island and 130 mi (200 km) west of Adak.

DAVIDOF VOLCANO (VNUM #311040)
51°57'15" N 178°19'34" E, Summit Elevation 1076 ft (328 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

An earthquake swarm in the vicinity of Davidof volcano that began on Monday, January 24, has continued this last week with small earthquakes detected each day. The rate of earthquakes was similar to previous weeks. Clouds obscured most satellite images. This earthquake activity may be associated with volcanic unrest, or it could be due to regional tectonic activity.

There is no real-time seismic monitoring network at Davidof volcano. The closest seismometers are approximately 9 miles (15 km) to the east of the volcano on Little Sitkin Island. Davidof is also monitored by satellite data and remote infrasound and lightning networks.

Davidof volcano is a mostly submerged stratovolcano in the Rat Islands group in the western Aleutian Islands, about 218 miles (350 km) west of Adak. The subaerial part of the volcano comprises Davidof, Khvostof, Pyramid, and Lopy islands, which encircle Crater Bay, a 1.5-mile (2.5 km) diameter caldera. The islands are built up from interbedded lava flows and explosive deposits. The volcano has been sparsely studied, but visits by Alaska Volcano Observatory geologists in 2021 documented thick sequences of rhyolite to dacite pyroclastic flow and fall deposits that represent the most recent explosive eruptions. The age of these deposits is unknown, but they appear older than Holocene deposits from nearby Segula and Little Sitkin. There are no known historical eruptions from Davidof.

OTHER ALASKA VOLCANOES

Information on all Alaska volcanoes is available at: http://www.avo.alaska.edu.

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CONTACT INFORMATION:

Michelle Coombs, Scientist-in-Charge, USGS, mcoombs@usgs.gov, (907) 786-7497

David Fee, Coordinating Scientist, UAFGI, dfee1@alaska.edu, (907) 322-4085

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.