These explosions were detected by local seismic sensors, local and regional infrasound sensors, and, when weather conditions allowed, in webcam and satellite images. Small explosions producing low-level ash clouds from the north crater of Mount Cerberus on Semisopochnoi Island occurred multiple times per day throughout the last week. Within the past 280 years a large explosive eruption produced pyroclastic flows that partially filled the Glacier Creek valley on the southwest flank.Ĭurrent Aviation Color Code: ORANGE The eruption at Semisopochnoi volcano continues.
A poorly documented eruption occurred in 1945, also producing a lava dome that was partially destroyed in the 1974 eruption. That eruption produced at least one ash cloud that likely exceeded an altitude of 25,000 ft above sea level.
A steep-sided lava dome, emplaced during the most recent significant eruption in 1974, occupies the center of the crater. The volcano is a composite structure consisting of an older dissected volcano and a younger parasitic cone with a 3 km-diameter summit crater. It is located 43 km (26 miles) east of the community of Adak.
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. Great Sitkin is monitored by local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks. Such 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. The terrain is steep in these areas, and blocks of lava and lava rubble could detach from the terminus of the flow lobes without warning and form small rock avalanches in these valleys. No ash emissions were observed and no local observations have been reported to AVO this week.Įrupted lava has overtopped the summit crater rim and is flowing into small valleys on the south, west, and north flank of the volcano. Elevated surface temperatures consistent with lava effusion were detected in satellite data all week when the volcano was not obscured by cloud cover. Geological Survey Friday, December 3, 2021, 12:56 PM AKST (Friday, December 3, 2021, 21:56 UTC) GREAT SITKIN VOLCANOĬurrent Aviation Color Code: ORANGE Lava effusion within the summit crater of Great Sitkin Volcano continues at a slow rate according to observations made throughout the week.
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