A roughly 3-m-high rounded glacial erratic at the Bumpass Hell parking lot is witness to the extensive glacial erosion that has affected much of Lassen Volcanic National Park. Brokeoff volcano in the background is the glacially eroded remnant of a large stratovolcano that formed begining about 600,000 years ago. At its peak the volcano may have reached a height of 3350 m. Glacial erosion of hydrothermally altered rocks at the core of the volcano has produced a large central depression.

Photo by Lee Siebert, 1998 (Smithsonian Institution).

This image is made available under the Public Domain Dedication CC0 license, but proper attribution is appreciated.

Lassen Volcanic Center