Mount Denison lies near the head of the Serpent Tongue, Hook, and Hallo glaciers NE of Snowy volcano. This poorly known section of Katmai National Park contains a cluster of four closely spaced and mostly ice-covered vents. Mount Denison lies at the SW end of this volcanic chain, which also includes Steller, Kukak, and Devils Desk volcanoes. Orientation of lava flows and a thick cross-bedded tephra deposit suggest that a vent is located near Mount Denison (Swanson, in Wood and Kienle 1990). The precise age of the most recent activity at Denison is not known.