Aniakchak National Monument and Preserve Aniakchak National Monument and Preserve Aniakchak has been referred to as the United States' most fascinating recent volcanic feature.
Aniakchak caldera is the largest along the Alaskan Peninsula.
Its volcanic history starts about 3,500 years ago when a dramatic explosion ejected 3,000 feet of mountain into the air. The remainder of this mountain then collapsed, leav ing a great crater. Since then many lesser eruptions have build up small cinder cones along with lava flows and explosion pits. The Aniakchak's most recent volcanic activity occurred in 1931, when an explosion ejected thousands of tons of ash into the atm osphere. Aniakchak is located on the Pacific Ocean rim of the what is called the Ring of Fire, which is a circle of volcanic hot spots associated with continental plate movement.