The 11 x 18 km Fisher caldera on western Unimak Island NE of Westdahl volcano is one of the largest calderas in the Aleutian arc. The caldera, which is elongated in a NE direction, formed around 9400 years ago, accompanied by emission of large-volume, mobile pyroclastic flows that reached the Bering Sea and the Pacific Ocean. Two satellitic cones are located below the north rim, NE of its 1112-m high point at Eickelberg Peak, which rises more than 900 m above three lakes on the caldera floor, one of which drains through a notch in the southern caldera rim. A large composite cone, Mount Finch, is found at the center of the caldera, which also contains a small breached cinder cone. Historical eruptions have occurred in the 18th and 19th centuries. Low-temperature fumaroles are located at the western flank of Mount Finch, and Turquoise Lake, at the base of the cone, emits hydrogen sulfide gas.
The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography.
Bindeman I A, Fournelle J H, Valley J W, 2001. Low-delta 18O tephra from a compositionally zoned magma body: Fisher caldera, Unimak Island, Aleutians. J Volc Geotherm Res, 111: 35-53.
Coats R R, 1950. Volcanic activity in the Aleutian Arc. U S Geol Surv Bull, 974-B: 35-47.
Fournelle J H, 1988. The geology and petrology of Shishaldin volcano, Unimak Island, Aleutian arc, Alaska. Unpublished PhD thesis, John Hopkins Univ, 507 p.
Gardner J E, Burgisser A, Stelling P, 2007. Eruption and deposition of the Fisher Tuff (Alaska): evidence for the evolution of pyroclastic flows. J Geol, 115: 417-435.
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.
Miller T P, Smith R L, 1977. Spectacular mobility of ash flows around Aniakchak and Fisher Calderas, Alaska. Geology, 5: 173-176.
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 Unpublished manuscript, unpaginated.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, 1975. Igneous-related geothermal systems. U S Geol Surv Circ, 726: 58-83.
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.
Stelling P, Gardner J E, Beget J, 2005. Eruptive history of Fisher caldera, Alaska, USA. J Volc Geotherm Res, 139: 163-183.