Sutter Buttes—The Lone Volcano in California’s Great Valley

The volcanic spires of the Sutter Buttes tower 2,000 feet above the farms and fields of California’s Great Valley, just 50 miles northnorthwest of Sacramento and 11 miles northwest of Yuba City. The only volcano within the valley, the Buttes consist of a central core of volcanic domes surrounded by a large apron of fragmental volcanic debris. Eruptions at the Sutter Buttes occurred in early Pleistocene time, 1.6 to 1.4 million years ago. The Sutter Buttes are not part of the Cascade Range of volcanoes to the north, but instead are related to the volcanoes in the Coast Ranges to the west in the vicinity of Clear Lake, Napa Valley, and Sonoma Valley.

The Sutter Buttes stand as a remarkable geographic and geologic feature of California’s Great Valley, and they remain a subject of scientific interest and research. One curious feature is the presence at the surface in the castellated core of a huge block, one-quarter mile across, of crystalline rock (Cretaceous granite) characteristic of the Sierran basement. This is one of many puzzles remaining for geologists to solve in future studies.

http://geology.com/usgs/sutter-buttes/