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 thick. Much of the volcano is mantled by snow and ice and several valley glaciers radiate out from the flanks.