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  • United States
  • Alaska
  • Stratovolcano
  • 1830 CE
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 54.65°N
  • 164.43°W

  • 1112 m
    3647 ft

  • 311350
  • Latitude
  • Longitude

  • Summit

  • Volcano

The Global Volcanism Program has no activity reports for Fisher.

The Global Volcanism Program has no Weekly Reports available for Fisher.

The Global Volcanism Program has no Bulletin Reports available for Fisher.

Volcano Types

Lava dome(s)

Tectonic Setting

Subduction zone
Continental crust (> 25 km)

Rock Types

Andesite / Basaltic Andesite
Basalt / Picro-Basalt
Trachyte / Trachyandesite


Within 5 km
Within 10 km
Within 30 km
Within 100 km

Geological Summary

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.

Eruptive History

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

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1830 Aug Unknown Confirmed 2 Historical Observations Mount Finch
1826 Oct 11 1827 Jan (?) Confirmed 3 Historical Observations Mount Finch
1795 (in or before) Unknown Confirmed   Historical Observations
0400 ± 50 years Unknown Confirmed   Radiocarbon (uncorrected) Turquoise cone
3170 BCE ± 75 years Unknown Confirmed 5 Radiocarbon (uncorrected) Turquoise cone
7420 BCE ± 200 years Unknown Confirmed 6 Radiocarbon (uncorrected) NE and SW parts of Fisher caldera

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.


Metrogoon Lake


Feature Name Feature Type Elevation Latitude Longitude
Eastern Mound Stratovolcano
Eickelberg Peak Stratovolcano 1094 m
Finch, Mount Stratovolcano 477 m 54° 40' 0" N 164° 22' 0" W
Neptune Cone Stratovolcano
Nick's Cone Cone
Turquoise Cone Stratovolcano


Feature Name Feature Type Elevation Latitude Longitude
Pyro Hill Maar

Photo Gallery

This 1974 view shows part of the interior of Fisher caldera on Unimak Island in the eastern Aleutian Islands. Fisher is an 11 x 18 km caldera that formed about 9100 years ago during the eruption of compositionally zoned ash flows that overtopped topographic barriers more than 500 m in elevation. The caldera contains two large lakes and a smaller lake that drains through a notch in the south caldera rim. There has been one poorly documented historical eruption from Fisher in 1826.

Photo by Tom Miller, 1974 (U.S. Geological Survey).


The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. 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.

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.

Affiliated Databases

Large Eruptions of Fisher Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.