Coso Range
The range is underlain principally by Mesozoic granitic rocks that are partly veneered by upper Cenozoic volcanic rocks of the Coso Volcanic Field. The volcanic units (in apparent decreasing age) include (1) widespread basaltic flows, (2) dacitic flows and tuff, and (3) rhyolitic domes and flows and basaltic cones and flows. These volcanic rocks are encompassed by an oval-shaped zone of late Cenozoic ring faulting that measures about 24 miles (39 km) east to west and 28 miles (45 km) north to south and that defines a structural basin. Most of the Coso Range and a slice of the adjacent Sierra Nevada lie within this ring structure. The youngest volcanic rocks are Pleistocene and, with associated active fumaroles, occupy a north-trending structural and topographic ridge about 11.2 by 6.2 miles (18 by 10 km) near the center of the basin. The ring structure and associated volcanic rocks suggest a large underlying magma chamber that has periodically erupted lava to the surface during the past few million years.
Prehistory
Numerous rock art sites (the Coso Rock Art District) are found in the range, left by the ancient Coso people. The prehistoric Coso inhabitants exported volcanic glass (Coso obsidian) and this highly valued toolstone has been found as far distant as the Channel Islands of California. Little Petroglyph Canyon and Renegade Canyon within the Range are open for guided tours through the Maturango Museum in Ridgecrest, California.