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News
Tuesday, Jun 02, 2015
A decline in seismicity over the last few months and no sign of activity in daily satellite images prompts AVO to downgrade Semisopochnoi volcano from Aviation Color Code YELLOW and Volcanic Alert Level ADVISORY to UNASSIGNED. (USGS) [more]
Current seismic signal at Semisopochnoi (AVO)
Thursday, Mar 26, 2015
The Alaska volcano observatory (AVO) detected significantly increased earthquake activity under the volcano and warns of a possible eruption: ... [more]
 

Semisopochnoi volcano

Stratovolcano 1221 m / 4,006 ft
United States, Aleutian Islands, 51.93°N / 179.58°E
Current status: restless (2 out of 5)
Semisopochnoi webcams / live data | Reports
Semisopochnoi volcano books
Last update: 23 Dec 2016
Typical eruption style: unspecified
Semisopochnoi volcano eruptions: 1987No recent earthquakes
TimeMag. / DepthDistanceLocation

Background:

Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km wide at sea level and contains an 8-km-wide caldera. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is 1221-m-high Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island's northern part. The three-peaked 774-m-high Mount Cerberus volcano was constructed during the Holocene within the caldera. Each of the peaks contains a summit crater; lava flows on the northern flank of Cerberus appear younger than those on the southern side. Other post-caldera volcanoes include the symmetrical 855-m-high Sugarloaf Peak SSE of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the NE part of the caldera. Most documented historical eruptions have originated from Cerberus, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone within the caldera could have been active during historical time.
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Smithsonian / GVP volcano information


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