The 2.5-km-wide Kaguyak caldera in the NE part of Katmai National Park is filled by a lake more than 180 m deep whose surface lies 550 m below the caldera rim. The volcano rises directly from lowland areas near sea level south of the Big River. Initially considered to be a typical stratovolcano truncated by a caldera, the pre-caldera edifice has been shown to consist of nine contiguous late-Pleistocene lava dome clusters, most of which lie east of the present caldera. A large post-caldera lava dome extends into the lake on the SW side and another dome forms a small island in the center of the lake. The caldera is unglaciated, and distal tephras from the caldera-forming eruption have been radiocarbon dated at about 5,800 years before present. Voluminous dacitic pyroclastic-flow deposits surround the caldera and reached Shelikof Strait to the SE.