Geologic Background:
The Coso volcanic field, located east of the
Sierra Nevada Range at the western edge of the Basin and
Range province consists of Pliocene to Quaternary
rhyolitic lava domes and basaltic cinder cones covering a
400 sq km area. Much of the volcanic field lies within
the China Lake Naval Weapons Center. The youngest
eruptions were chemically bimodal, forming basaltic lava
flows along with 38 rhyolite lava flows and domes, most
with youthful, constructional forms. The latest dated
eruption formed the Volcano Peak basaltic cinder cone and
lava flow and was Potassium-Argon dated at 39,000 +/-
33,000 years ago. Although most activity ended during the
late Pleistocene, the youngest lava dome may be of
Holocene age based on geomorphological evidence.
Historic Activity:
- Active fumaroles and thermal springs are present in
an area that is a producing geothermal field.
Recent Activity:
- Fumaroles are present and volcanic field is also well
known as a geothermal area.
- Seismic swarms have occurred in the past, as in 1982
when thousands of events were recorded, the largest a
magnitude 4.9. Another seismic swarm occurred in February
1992, with activity peaking on Feb. 20. More than 300
small high-frequency earthquakes were recorded, the
largest was a magnitude 4.0 on Feb. 19.
Data Sources:
- Global Volcanism Network (V. 17, No. 2).
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