BackgroundThe 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.
Smithsonian / GVP volcano information
See also: Sentinel hub | Landsat 8