I follow CA-20 down through the foothills of the Sierra, and cross California's Great Valley. Sutter Buttes rise 2000 feet as the eroded remnants of the valley's only volcanic feature. In 1849 James Dwight Dana first recognized them as the remains of an extinct volcano, now known to have been active from 1.6 to 1.4 million years ago.
All images copyright © 2014 F.W. Vollmer and may not be used without permission.