Yunaska is the largest of the Islands of Four Mountains

Islands of Four Mountains

Islands of Four Mountains is an island grouping of the Aleutian Islands in Alaska, United States. The chain includes, from west to east, Amukta, Chagulak, Yunaska, Herbert, Carlisle, Chuginadak, Uliaga, and Kagamil Islands. This island chain is located between Amukta Pass and the Andreanof Islands...

 group in the Aleutian Islands of southwestern Alaska

Alaska

Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

, United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. It has a land area of 66.834 sq mi (173.099 km²) and no population at the 2000 census

United States Census, 2000

The Twenty-second United States Census, known as Census 2000 and conducted by the Census Bureau, determined the resident population of the United States on April 1, 2000, to be 281,421,906, an increase of 13.2% over the 248,709,873 persons enumerated during the 1990 Census...

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The island comprises two volcanic mountains, with a valley between. The western mountain is composed of four overlapping and eroded stratovolcanoes, with a cinder cone field at the western end. It has not been historically active. The eastern mountain is a large shield volcano with two overlapping summit calderas, which last erupted in 1937.