Aniakchak National Monument and Preserve Volcanoes

Aniakchak Crater lies in the historically active volcanic belt of the Aleutian Mountain Range. The crater is, to be precise, a dry caldera, remnant of a mountain hollowed out by explosion and collapse. Aniakchaks' outer slopes are characterized as having sparse vegetation, barren ash flows, precipitous cliffs, and tilted rock strata. The interior of the caldera contains examples of almost every kind of volcanic feature: lava flows, areas of unusually high ground temperature, cinder cones, a lava plug, warm springs, explosion pits, and layers of volcanic and sedimentary rocks exposed by volcanic action. Vent Mountain, one of the cinder cones, rises 2,200 feet above the caldera floor. Since cinder cones rarely exceed 1,000 feet in height, Vent Mountain is unusually high. In the top of the Vent there is a crater about 2,000 feet in diameter. Other cinder cones in the caldera are over 200 feet high. The caldera averages 6 miles in diameter and encompasses about 30 square miles. The lowest point on the floor is 1,100 feet above sea level. Some of the highest points are at Aniakchak Peak, reaching heights of about 4,400 feet.