Bristlecone Pine and Wizard Island

Volcano Status: Dormant.
Age/Last Eruption: Crater Lake began about 500,000 years ago as Mount Mazama, a progressively building volcanic cone. About 7,700 years ago, cataclysmic eruptions, 42 times greater than those of Mount St. Helens in 1980, spewed ash over 5,000 square miles. The eruptions covered parts of 8 U.S. states and 3 Canadian provinces with 6 inches of ash. Some local areas were buried in over 50 feet of ash. After the volcano's magma chamber had emptied, the top of the mountain collapsed, resulting in a caldera. Up until about 4,000 years ago, volcanic activity within the caldera prevented the formation of a lake and built the cinder cones Wizard Island and the submerged Merriam Cone. Over the last 4,000 years, the volcano has been quiet, and the lake began to fill the caldera. Crater Lake is now the deepest lake in the United States with a maximum depth of 1,932 feet (589 meters) and an average depth of 1,500 feet (457 meters).
Peak Elevation: 8,151 feet (2,484 meters); Mount Mazama originally attained an elevation of 12,000 feet (3,650 meters).
Volcano Type/Deposits: Caldera. Composed of basalt to rhyolite lava and pyroclastic deposits.

Print No. A99NW-20-11.