This is an image of Crater Lake in Oregon, USA.
Click on image for full size
Image from: U.S. Geological Survey

Crater Lake

Mt. Mazama was once among a cluster of stratovolcanoes stretching along the Washington and Oregon coast. This cluster of volcanoes includes Mt. Hood, Mt. Rainier, and Mt. St. Helens. The magma chamber under Mt. Mazama took 15,000-40,000 yrs to form.

During the few centuries preceding the last, climactic eruption, at least two other large eruptions occurred. Ash and pumice from one of these eruptions extended into eastern Washington and western Nevada.

The last climactic eruption of Mt. Mazama occured 6850 years ago, over a number of months, and produced major outbursts of ash, lava, and hot vapors. Deposits from this series of eruptions have been found in 8 western states and 3 Canadian provinces.

Following the final series of eruptions, the cone of the volcano collapsed into the magma chamber, and Mt Mazama became dormant except for activity which formed a small cinder cone in the center (shown in this picture). The collapsed volcano filled with water and became what we now know as Crater Lake.

The Yakima Indians who lived near Mt. Mazama when it collapsed have a different story of what caused the mountain to fall.

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