The Shishaldin Volcano is one of the most active volcanoes in the Aleutian arc. It has erupted at least 29 times since 1775. The cone has a base diameter of approximately 10 miles (16 km). The most recent eruptive period occurred in April-May 1999.
Mt. Isanotski is a stratovolcano, also known as "Ragged Jack" for its rugged and jagged features, that is located on Unimak Island in the Aleutian island chain. It has not erupted since the 1840s.