page_title: Mount Katmai
section_title: Geology
hierarchical_section_title: Mount Katmai / Geology
caption_attribution_description: English: Katmai caldera before and after surveys of 1908 and 1951
context_page_description: Mount Katmai is a large 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. The mountain is located in Kodiak Island Borough, very close to its border with Lake and Peninsula Borough.
context_section_description: Mount Katmai is one of five vents encircling the Novarupta volcano, source of the VEI 6 eruption and associated voluminous pyroclastic flows in 1912. The volcano has caused ten known fatalities due to gas exposure. Katmai consists chiefly of lava flows, pyroclastic rocks, and non-welded to agglutinated air fall. The Quaternary volcanic rocks at Katmai and adjacent cones are less than 5,000 ft (1,500 m) thick. Much of the volcano is mantled by snow and ice and several valley glaciers radiate out from the flanks.
  Katmai volcano is built on the sedimentary rocks of the Naknek Formation of Late Jurassic age, which are exposed just west of the caldera rim at an elevation of about 5,000 feet (1,520 m), as well as north and southeast of the crater. Sedimentary rocks have been reported at an elevation of over 6,000 feet (1,830 m) in the west wall of the caldera and near the bottom of the eastern wall near 3,400 ft (1,040 m).
caption: Katmai caldera before and after surveys of 1908 and 1951
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