Coso Volcanic Field

Photo of this volcano
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 36.03°N
  • 117.82°W

  • 2400 m
    7872 ft

  • 323180
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

Most Recent Bulletin Report: February 1992 (BGVN 17:02) Citation IconCite this Report


Tectonic earthquake swarm

A seismic swarm started on 17 February, with activity peaking by 20 February, and still declining as of 26 February (figure 1). More than 300 small high-frequency earthquakes (eight with M > 3.0) were recorded, the largest (M 4.0) at 0319 on 19 February. Hypocenters show a 3-km-long pattern elongated to the NNW, at 3-5 km depths (figure 2). The focal mechanism for the largest event showed mainly strike-slip motion (right-lateral on a N-S plane, or left-lateral on an E-W plane), with a small normal component. There were no reports of injuries or damages.

Figure (see Caption) Figure 1. Hourly number of earthquakes in the Coso Mountains, 17-26 February 1992. Courtesy of the USGS.
Figure (see Caption) Figure 2. Epicenter map (top) and E-W cross-section showing focal depths (bottom) of >300 high-frequency earthquakes recorded in the Coso Mountains, 17-26 February 1992. Courtesy of the USGS.

The Coso region is an active geothermal area that has had seismic swarms in the past, as in 1982 when thousands of events were recorded, the largest M 4.9. The Volcano Peak cinder cone and lava flow, apparently the youngest features in the Coso Mountains, are believed to have been erupted 0.039 ± 0.033 mybp. (K/Ar age).

Information Contacts: J. Mori and W. Duffield, USGS.

The Global Volcanism Program has no Weekly Reports available for Coso Volcanic Field.

Bulletin Reports - Index


Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

02/1992 (BGVN 17:02) Tectonic earthquake swarm




Information is preliminary and subject to change. All times are local (unless otherwise noted)


February 1992 (BGVN 17:02) Citation IconCite this Report


Tectonic earthquake swarm

A seismic swarm started on 17 February, with activity peaking by 20 February, and still declining as of 26 February (figure 1). More than 300 small high-frequency earthquakes (eight with M > 3.0) were recorded, the largest (M 4.0) at 0319 on 19 February. Hypocenters show a 3-km-long pattern elongated to the NNW, at 3-5 km depths (figure 2). The focal mechanism for the largest event showed mainly strike-slip motion (right-lateral on a N-S plane, or left-lateral on an E-W plane), with a small normal component. There were no reports of injuries or damages.

Figure (see Caption) Figure 1. Hourly number of earthquakes in the Coso Mountains, 17-26 February 1992. Courtesy of the USGS.
Figure (see Caption) Figure 2. Epicenter map (top) and E-W cross-section showing focal depths (bottom) of >300 high-frequency earthquakes recorded in the Coso Mountains, 17-26 February 1992. Courtesy of the USGS.

The Coso region is an active geothermal area that has had seismic swarms in the past, as in 1982 when thousands of events were recorded, the largest M 4.9. The Volcano Peak cinder cone and lava flow, apparently the youngest features in the Coso Mountains, are believed to have been erupted 0.039 ± 0.033 mybp. (K/Ar age).

Information Contacts: J. Mori and W. Duffield, USGS.

The Global Volcanism Program is not aware of any Holocene eruptions from Coso Volcanic Field. If this volcano has had large eruptions (VEI >= 4) prior to 10,000 years ago, information might be found on the Coso Volcanic Field page in the LaMEVE (Large Magnitude Explosive Volcanic Eruptions) database, a part of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Photo Gallery


The Coso volcanic field at the western edge of the Basin and Range province consists of largely Pliocene to late-Pleistocene rhyolitic lava domes and basaltic cinder cones covering a 400 sq km area. This view looks south across the range from Cactus Peak with some of the 38 light-colored rhyolitic lava domes of the Coso volcanic field in the foreground and dark-colored basaltic cinder cones and associated lava flows in the background. Active fumaroles and thermal springs are present in an area that is a producing geothermal field.

Photo by Paul Kimberly, 1997 (Smithsonian Institution).
See title for photo information.
Bubbling mudpots are abundant in the Coso Hot Springs on the eastern margin of the Coso volcanic field. The hot springs occur along faults at the margins of a horst capped by rhyolitic rocks and are associated with fumaroles, mudpots, and widespread areas of hydrothermally altered ground.

Photo by Paul Kimberly, 1997 (Smithsonian Institution).
See title for photo information.
A cooperative program of the U.S. Navy China Lake Naval Weapons Station and private industry has developed geothermal power at the Coso volcanic field. The first well was drilled in 1981 and production now exceeds 250 megawatts, greatly reducing energy costs to the Navy and providing additional electricity to the southern California power grid. This view from the NW shows turbine plants and production well ponds at Coso. Devils Kitchen, a fumarolic area with extensively hydrothermally altered ground, appears at the upper right.

Photo by Paul Kimberly, 1997 (Smithsonian Institution).
See title for photo information.
Red Cone, a basaltic cinder cone at the western margin of the Coso volcanic field, is a prominent landmark visible from Highway 395, which follows the eastern margin of the Sierra Nevada Range. The late-Pleistocene cinder cone is the largest of a group of isolated cones along the valley floor. An area of more concentrated young basaltic cones and lava flows occurs to the SE along the crest of the volcanic horst forming the Coso Range.

Photo by Paul Kimberly, 1997 (Smithsonian Institution).
See title for photo information.
The Sugarloaf Mountain lava dome and associated lava flows, seen here from the west, is the largest of 38 rhyolitic lava domes of the Coso volcanic field, rising 300 m above its base. The high-silica rhyolite of Sugarloaf Mountain contains localized areas of obsidian that were used as a source of arrowheads for native Americans. The dome has been dated at about 41,000 +/- 21,000 years and is one of the youngest volcanic vents at Coso.

Photo by Lee Siebert, 1997 (Smithsonian Institution).
See title for photo information.
Red Cone (center) is the largest of a group of isolated basaltic scoria cones and lava flows on the floor of the Rose Valley in the western part of the Coso volcanic field. The late-Pleistocene scoria cone is seen here from the NE, with the towering fault scarp of the Sierra Nevada Range in the background. Highway 395 traverses Rose Valley between the cone and the Sierras.

Photo by Lee Siebert, 1997 (Smithsonian Institution).
See title for photo information.
A series of basaltic cinder cones and related lava flows at the southern end of the Coso volcanic field form some of the youngest volcanic products at Coso. The cones and flows are concentrated along the south edge of a NE-trending horst that is capped by rhyolitic lava domes and flows. Many of the flows, such as the one left of center, are intracanyon flows that traveled down existing drainages.

Photo by Lee Siebert, 1997 (Smithsonian Institution).
See title for photo information.

Smithsonian Sample Collections Database


The following 51 samples associated with this volcano can be found in the Smithsonian's NMNH Department of Mineral Sciences collections. Catalog number links will open a window with more information.

Catalog Number Sample Description
NMNH 117460-100 Rhyolite
NMNH 117460-101 Rhyolite
NMNH 117460-102 Rhyolite
NMNH 117460-103 Rhyolite
NMNH 117460-104 Obsidian
NMNH 117460-105 Perlite
NMNH 117460-106 Obsidian
NMNH 117460-107 Obsidian
NMNH 117460-108 Obsidian
NMNH 117460-109 Rhyolite
NMNH 117460-110 Rhyolite
NMNH 117460-111 Rhyolite
NMNH 117460-112 Rhyolite
NMNH 117460-113 Rhyolite
NMNH 117460-114 Rhyolite
NMNH 117460-115 Rhyolite
NMNH 117460-116 Rhyolite
NMNH 117460-117 Rhyolite
NMNH 117460-159 Rhyolite
NMNH 117460-160 Rhyolite
NMNH 117460-161 Rhyolite
NMNH 117460-162 Rhyolite
NMNH 117460-163 Obsidian
NMNH 117460-164 Obsidian
NMNH 117460-165 Rhyolite
NMNH 117460-166 Obsidian
NMNH 117460-167 Obsidian
NMNH 117460-168 Rhyolite
NMNH 117460-169 Pumice
NMNH 117460-172 Rhyolite
NMNH 117460-173 Rhyolite
NMNH 117460-74 Marekanite
NMNH 117460-81 Rhyolite
NMNH 117460-82 Rhyolite
NMNH 117460-83 Rhyolite
NMNH 117460-84 Rhyolite
NMNH 117460-85 Perlite
NMNH 117460-86 Obsidian
NMNH 117460-87 Obsidian
NMNH 117460-88 Rhyolite
NMNH 117460-89 Rhyolite
NMNH 117460-90 Obsidian
NMNH 117460-91 Obsidian
NMNH 117460-92 Obsidian
NMNH 117460-93 Obsidian
NMNH 117460-94 Obsidian
NMNH 117460-95 Obsidian
NMNH 117460-96 Obsidian
NMNH 117460-97 Obsidian
NMNH 117460-98 Obsidian
NMNH 117460-99 Rhyolite

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