• Aerial view of Aniakchak Caldera taken from northern rim


    National Monument & Preserve Alaska

Natural Features & Ecosystems

Looking into the Caldera from The Gates, Troy Hamon, NPS Chief of Resource Management
Looking into the Caldera from The Gates.
NPS Photo by Troy Hamon
Aniakchak Caldera is a raw and rugged volcanic feature located in a landscape that is, because of its remoteness, little affected by human occupancy. Plant and animal communities are in tune with the natural phenomena that control their habitat. Volcanic activity has subsided since the last eruption in 1931, but the geologic processes that follow such activity continue to weather, erode, and redistribute the volcanic materials. Hot spots and warm springs on the caldera floor indicate that eruptive activity may resume at any time.

Did You Know?

Did You Know?

The outlet of the Aniakchak River, referred to as "The Gates," was formed when water within the caldera breached the rim and carved through the wall. Terrace deposits above the current water level of Surprise Lake indicate that the lake once filled 50 percent more of the caldera.