What is a Volcanic Crater Lake?

Volcanic crater lakes are formed as a result of volcanic activity that occurred thousands of years ago. During an eruption, magma present in the magma chamber under the volcano is expelled, often very forcefully. When the magma chamber empties, the support that the magma had provided inside the chamber disappears. As a result the sides and top of the volcano collapse inward creating a crater or caldera.

Some calderas form a lake as the bowl shaped depression fills with water, usually from precipitation. A famous example of this is Crater Lake in Klamath County, Oregon. This caldera formed over 7,700 years ago when a stratovolcano, Mt. Mazama, violently erupted.

Mount Mazama

Mount Mazama was an important symbol to the native Makalak people who lived in the surrounding areas. Makalak legend says hat the collapse of the mountain was caused by a brutal battle between the spirit of the sky and the spirit of the mountain. The eruption signaled the end of the battle, but the native tribes mourned the loss of the volcano that they had considered sacred.

For several thousand years after the major eruption, there were a number of smaller eruptions that continued inside the caldera. One was so big that it formed an island in Crater Lake called Wizard Island.

Is Crater Lake Considered to be an Active Volcano?

The last known eruption at Crater Lake occurred when a small lava dome erupted under water on the east flank of the base of Wizard Island about 4,800 years ago. Since that time, the volcano has remained quiet, allowing as much as 100 feet of sediment to accumulate on the lake bottom. Although the volcano that formed Crater Lake is considered dormant, Crater Lake is still monitored closely by the United States Geological Survey Cascades Volcano Observatory seismic monitoring network.

Where Is Crater Lake?

Crater Lake National Park is in Klamath County, a premier destination for popular attractions and secret discoveries. In addition to Crater Lake National Park, Klamath County is home to four national forests and 4 national wildlife refuges. The county is named for the Klamath tribe of Native Americans that populated the area when the first European explorers arrived in the mid-19th century. For more information about Klamath County, order a free visitors guide. Better yet, come to Klamath County and see for yourself!