The Coso Volcanic Field is located in Inyo County, California, at the western edge of the Basin and Range geologic province and northern region of the Mojave Desert.

Initiation of volcanism at Coso preceded the onset of Basin and Range crustal extension there, as expressed by normal faulting.

The earlier of the two principal periods of volcanism began with the emplacement of basalt flows over a surface of little relief.

Obsidian is exposed locally on most extrusions, and analyses of fresh glass indicate that all of the rhyolite is of the so-called high-silica variety; SiO2 content is essentially constant at 77 percent.

The chief period of exploitation was between approximately 3000 and 1000 years ago, when people mined obsidian by constructing benches in hillsides and digging deep pits to access raw materials (Elston and Zeier 1984; Gilreath and Hildebrand 1997).

A multi-disciplinary program of geothermal assessment carried out in the 1970s defined a potential resource of 650 megawatts electric with a nominal life span of 30 years.

[4] The Coso Volcanic Field is one of the most seismically active regions in the United States, producing dozens of tremors in the M1 and M2 range each week.

On July 4th and 5th, 2019 two large earthquakes sparked a surge of activity in the area in and around the Coso Volcanic Field.

Within a week, more than 8000 (M1.0-4.5) smaller earthquakes had joined the swarm, though only 27 quakes larger than M4.5 occurred after the largest events.

[6] Earthquake swarms are common in the Coso area, often producing hundreds of tremors over periods as short as a few days.