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| Space Shuttle photo STS047-077-034 looking north-northwest across southern Unimak Island to Fisher caldera. Photo taken in September 1992. |
Fisher is an andesite stratovolcano capped by a caldera. The volcanic center has a volume of about 300 cubic km and a diameter of about 21 km. The stratovolcano has been deeply eroded and glaciated. The caldera is 11 by 18 km and contains two lakes. There are several cinder and spatter cones in the caldera, some up to 2 km is diameter and 400 m in height. Ash-flow tuffs that blanket parts of the volcano are compositionally-zoned from basal dacite (64% silica) up to basaltic andesite (53% silica). The ashflows were very mobile, traversing 15 km and climbing 500 m up nearby mountains. Fisher had a caldera-forming eruption ca. 9100 years ago. Fisher had a poorly documented ash-producing eruption in 1826.
Simkin, T., and Siebert, L., 1994, Volcanoes of the World: Geoscience Press, Tucson, Arizona, 349 p.
Charles A. Wood & Jurgen Kienle, 1990, Volcanoes of North America: United States and Canada, Cambridge University Press, Cambridge, p. 45.
Wood, C.A., and Kienle, J., 1993, Volcanoes of North America: Cambridge University Press, New York, 354 p.
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