Coso Volcanic Field

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  • Volcanic Region
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  • Last Known Eruption
  • 36.03°N
  • 117.82°W

  • 2400 m
    7872 ft

  • 323180
  • Latitude
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Most Recent Bulletin Report: February 1992 (BGVN 17:02)


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 1. Hourly number of earthquakes in the Coso Mountains, 17-26 February 1992. Courtesy of the USGS.
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.

Index of Bulletin Reports


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




Bulletin Reports

All information contained in these reports is preliminary and subject to change.


02/1992 (BGVN 17:02) 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 1. Hourly number of earthquakes in the Coso Mountains, 17-26 February 1992. Courtesy of the USGS.
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.
Download or Cite this Report

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. Active fumaroles and thermal springs are present in an area that is a producing geothermal field. The youngest eruptions were chemically bimodal, forming basaltic lava flows along with 38 rhyolitic 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 (Monastero 1998, pers. comm.).

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.


Synonyms

Coso Range

Cones

Feature Name Feature Type Elevation Latitude Longitude
Volcano Butte Cone
Volcano Peak Cone

Domes

Feature Name Feature Type Elevation Latitude Longitude
Cactus Peak Dome
Sugarloaf Mountain Dome

Thermal

Feature Name Feature Type Elevation Latitude Longitude
Coso Hot Springs Hot Spring
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).
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).
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).
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).
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).
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).
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).

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

Coombs H A, Howard A D, 1960. United States of America. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 9: 1-68.

Duffield W A, Bacon C R, 1981. Geologic map of the Coso volcanic field and adjacent areas, Inyo County, California. U S Geol Surv Misc Invest Ser Map, I-1200, 1:50,000.

Duffield W A, Bacon C R, Dalrymple G B, 1980. Late Cenozoic volcanism, geochronology, and structure of the Coso Range, Inyo County, California. J Geophys Res, 85: 2381-2404.

Monastero F C, 2002. Model for sucess: an overview of industry-military cooperation in the development of power operations at the Coso geothermal field in southern California. Geotherm Res Council Bull, 31: 188-195.

Monastero F C, 1998. . (pers. comm.).

Smith R L, Shaw H R, 1975. Igneous-related geothermal systems. U S Geol Surv Circ, 726: 58-83.

Wood C A, Kienle J (eds), 1990. Volcanoes of North America. Cambridge, England: Cambridge Univ Press, 354 p.

Volcano Types

Lava dome(s)
Pyroclastic cone(s)
Tuff ring(s)

Tectonic Setting

Rift zone
Continental crust (> 25 km)

Rock Types

Major
Rhyolite
Basalt / Picro-Basalt
Dacite
Andesite / Basaltic Andesite

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km
370
370
577
71,942

Affiliated Databases

Large Eruptions of Coso Volcanic Field Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.