Mount Katmai is a volcano with glacier-covered walls and a large crater, located near the head of the Alaska Peninsula, in Katmai National Park. It was once much higher, but a violent eruption in 1912 collapsed the mountain. Its crater today is eight miles in circumference and 3,700 feet deep, and holds a lake with a small island. It rises near the shore of the Shelikof Straight, across which Kodiak Island can be seen. Aniakchak and the Aleutian Islands are further south on the same peninsula.
The valley surrounding Katmai is known as the Valley of Ten Thousand Smokes because of the widespread steam and smoke which have risen from the valley floor for much of this century. The volcanic activity was at its zenith just following the eruption of 1912. Only a few vents are still active.