Skip to main content.


18. Mazama Deposits: a jewel born of destruction

Exotic Terranes

Just 7,700 years ago, Mount Mazama, an active, 12,000-foot tall High Cascade volcano, exploded in a massive eruption that blew 50 cubic miles of rock and ash into the air. The eruption blanketed the surrounding landscape with red-hot flows of ash and pumice and produced a cloud of ash that rained down over an area covering eight western states and three Canadian provinces. What was left of the volcano collapsed on itself, leaving a gaping hole that subsequently filled with snow melt to form Oregon’s iconic Crater Lake, today Oregon’s only national park. The amount of material erupted would cover the entire state to a depth of almost three feet.

OGDC units: includes all mapped Holocene air fall and ash flow deposits from the climatic Mazama eruption

U.S. Geological Survey Scientific Investigations Map 2832, Geologic Map of Mount Mazama and Crater Lake Caldera, Oregon

Age Range: 7,700 years ago
Rock Types: ash, tuff
Did You Know? A layer of ash from Mount Mazama has been found in Edmonton, Alberta, more than 800 miles away.
square bullet Go See It!
Crater Lake National Park
Annie Canyon (near Crater Lake)


« Back    Continue »