Crooked River caldera
The Crooked River caldera is a large and ancient volcano that straddles three central Oregon counties. The diameter of the caldera is about 41 km x 27 km and is notable for the welded tuff present at Gray Butte, Smith Rock, Powell Buttes, Grizzly Mountain and Barnes Butte. The volcano is considered extinct and last erupted about 29.5 Ma.
