Mount Katmai is a large active stratovolcano on the Alaska Peninsula in southern Alaska, located within Katmai National Park and Preserve. It is about 6.3 miles in diameter with a central lake-filled caldera about two by three miles in size, formed during the Novarupta eruption of 1912. The caldera rim reaches a maximum elevation of 6,716 feet. In 1975 the surface of the crater lake was at an elevation of about 4,220 feet, and the estimated elevation of the caldera floor is about 3,400 ft.