Find U.S. Volcano
Crater Lake partly fills one of the most visually spectacular calderas of the world, an 8-by-10-km (5-by-6-mi) basin more than 1 km (0.6 mi) deep formed by collapse of the volcano known as Mount Mazama during a series of explosive eruptions about 7,700 years ago.
Location: Oregon, Klamath County
Latitude: 42.93° N
Longitude: 122.12° W
Elevation: 2,487 (m) 8,159 (f)
Volcano type: Caldera
Composition: Basalt to Rhyolite
Most recent eruption: 6,600 years ago
Threat Potential: Very High*
*based on the National Volcano Early Warning System
Having a maximum depth of 594 m (1,949 ft), Crater Lake is the deepest lake in the United States. Mount Mazama straddles the Cascade volcanic axis and is a cluster of overlapping stratovolcanoes that is the most voluminous Quaternary volcanic system in the Oregon Cascades. The volcano's compound edifice has been active relatively continuously since 420,000 years ago, and it is built mostly of andesite to dacite until it began erupting rhyodacite about 30,000 years ago, ramping up to the caldera-forming eruption. Excellent preservation and easy access make Mount Mazama, Crater Lake caldera, and the deposits formed by the climactic eruption constitute a natural laboratory for study of volcanic and magmatic processes. Research relating to the caldera-forming eruption has been of fundamental importance to volcanologists, helping them to understand large explosive eruptions, compositional zonation in magma chambers, and collapse caldera mechanisms. The climactic eruption is also the source of the widespread Mazama ash, a useful Holocene stratigraphic marker throughout the Pacific Northwest, adjacent Canada, and offshore.