Unimak o͞oˈnĭmăk, yo͞oˈ– [key], volcanic island, 70 mi (113 km) long, off W Alaska. It is the largest of the Aleutian Islands, and nearest to the Alaska Peninsula. The highly symmetrical, cone-shaped Mt. Shishaldin (9,373 ft/2,857 m), one of the most active volcanoes in the Aleutian arc, is on Unimak.

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