Duncan Peak, California, USA
(c) 2003 Andrew Alden, licensed to About.com, Inc. (fair use policy)
Duncan Peak dominates the western skyline of Hopland, California, in Mendocino County. The floodplain in the foreground is part of the Sanel Valley, a downdropped block along the Maacama fault system. This fault system is one thread of the wide set of faults, including the San Andreas fault to the west of here, that accommodates the motion between the North American and Pacific crustal plates. A short distance to the east is The Geysers, where a subterranean steam field supports the world's largest geothermal power facility. Here's an introduction to geothermal power.