Katmai Caldera, a collapse feature that formed during the catastrophic eruption of nearby Novarupta volcano in June, 1912, is a steep-walled, 1.5-km (1 mi)-diameter crater which truncates a formerly 2,290-m (7,513 ft)-high stratovolcano. The caldera is partially filled by a blue-green lake about 250 m (820 ft) deep. The lake level was still rising when last measured in the mid-1970's. Photograph by C. Neal, U.S. Geological Survey, June 4, 1990.
Image courtesy of AVO / U.S. Geological Survey.