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  • Country
  • Subregion Name
  • Primary Volcano Type
  • Last Known Eruption
  • 51.93°N
  • 179.58°E

  • 1221 m
    4005 ft

  • 311060
  • Latitude
  • Longitude

  • Summit

  • Volcano

There are no activity reports for Semisopochnoi.

 Available Weekly Reports

There are no Weekly Reports available for Semisopochnoi.

Summary of eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1987 Apr 13 Unknown Confirmed 2 Historical Observations Sugarloaf ?
1873 Unknown Confirmed   Historical Observations Cerberus
[ 1830 ] [ Unknown ] Uncertain     Cerberus
[ 1792 ] [ Unknown ] Uncertain     Cerberus
[ 1790 ] [ Unknown ] Uncertain     Cerberus
[ 1772 ] [ Unknown ] Uncertain     Cerberus

The following references are the sources used for data regarding this volcano. References are linked directly to our volcano data file. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title. Additional discussion of data sources can be found under Volcano Data Criteria.

Coats R R, 1950. Volcanic activity in the Aleutian Arc. U S Geol Surv Bull, 974-B: 35-47.

Coats R R, 1959a. Geologic reconnaissance of Semisopochnoi Island western Aleutian Islands Alaska. U S Geol Surv Bull, 1028-O: 477-519.

Delong S E, Perfit M R, McCulloch M T, Ach J, 1985. Magmatic evolution of Semisopochnoi Island, Alaska: trace-element and isotopic constraints. J Geol, 93: 609-618.

Henning R A, Rosenthal C H, Olds B, Reading E (eds), 1976. Alaska's volcanoes, northern link in the ring of fire. Alaska Geog, 4: 1-88.

IAVCEI, 1973-80. Post-Miocene Volcanoes of the World. IAVCEI Data Sheets, Rome: Internatl Assoc Volc Chemistry Earth's Interior..

Miller T P, McGimsey R G, Richter D H, Riehle J R, Nye C J, Yount M E, Dumoulin J A, 1998. Catalogue of the historically active volcanoes of Alaska. U S Geol Surv Open-File Rpt, 98-582: 1-104.

Motyka R J, Liss S A, Nye C J, Moorman M A, 1993. Geothermal resources of the Aleutian arc. Alaska Div Geol Geophys Surv, Prof Rpt, no 114, 17 p and 4 map sheets.

Myers J D, 1994. The Geology, Geochemistry and Petrology of the recent Magmatic Phase of the Central and Western Aleutian Arc. Unpublished manuscript, unpaginated.

Smith R L, Shaw H R, Luedke R G, Russell S L, 1978. Comprehensive tables giving physical data and thermal energy estimates for young igneous systems of the United States. U S Geol Surv Open-File Rpt, 78-925: 1-25.

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.