Round Mountain (center), seen here from the WNW with the hills of the California Coast Range in the background, is one of a series of basaltic-andesite cinder cones erupted along a N-S-trending line at the eastern margin of the Clear Lake volcanic field. These cones form some of the youngest products of the volcanic field. Lava flows from Round Mountain extend west into High Valley (lower right) and east to the North Fork Cache River. The background hills are composed of Cretaceous-Jurrasic metamorphic rocks of the Franciscan formation.

Photo by Paul Kimberly, 1997 (Smithsonian Institution).

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

Clear Lake Volcanic Field