Fisher Volcano, USA
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Fisher Volcano, USA
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.
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.
PHOTO SOURCE: Tom Miller, 1974 (U.S. Geological Survey), courtesy of the Global Volcanism Program, Smithsonian National Museum of Natural History, used with permission.
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