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 by 27 kilometres (25 mi × 17 mi) 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.^[1]

Crooked River caldera
Crooked River caldera
Highest point
Coordinates	44°18′N 120°54′W
Geography
Location	Deschutes, Crook, and Jefferson counties, Oregon, U.S.
Geology
Rock age	29.5 Ma
Mountain type(s)	Caldera, supervolcano
Volcanic arc	Cascade Volcanic Arc, Ochoco Mountains
Last eruption	29.5 million years ago

References

1. The Crooked River Caldera is also a supervolcano. "Field trip guide to the Oligocene Crooked River caldera: Central Oregon's Supervolcano, Crook, Deschutes, and Jefferson Counties, Oregon" (PDF). Oregon Geology. Oregon Department of Geology and Mineral Studies. 2009. Retrieved 2014-12-29.