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| Volcanic Field of Southern California | |
|---|---|
| Name | Volcanic Field of Southern California |
| Caption | Composite map of volcanic centers in southern California and adjacent regions |
| Location | Southern California, United States |
| Elevation | Variable |
| Type | Monogenetic volcanic field, basaltic cinder cones, lava flows, rhyolitic domes |
| Age | Pleistocene–Holocene |
| Last eruption | Holocene (disputed) |
Volcanic Field of Southern California is a dispersed ensemble of volcanic centers, cinder cones, lava flows, and volcanic vents distributed across southern California and adjacent parts of Baja California, near tectonic boundaries including the San Andreas Fault, the Garlock Fault, and the transition to the Gulf of California. The field records interactions between the Pacific Plate, the North American Plate, transtensional basins such as the Salton Trough, and regional crustal structures including the Mojave Desert and the Peninsular Ranges. Its features have been studied by geologists from institutions such as the United States Geological Survey, the California Geological Survey, and universities including California Institute of Technology, University of California, Los Angeles, and University of California, Berkeley.
The field lies within a tectonic mosaic shaped by plate boundaries exemplified by the San Andreas Fault system, the plate-bounding transform adjacent to the Gulf of California rift, and the diffuse shear that affects the Mojave Desert and the Salton Trough. Regional tectonics involve interaction among the Pacific Plate, the North American Plate, the Cocos Plate, and the microplate blocks of Baja California. Volcanism is linked to transtensional basins such as the Salton Sink, pull-apart basins like San Gorgonio Pass, and lithospheric processes beneath the Peninsular Ranges Batholith. Studies reference work by researchers associated with Scripps Institution of Oceanography, Stanford University, and the Geological Society of America on stress fields and crustal thinning.
The volcanic field comprises discrete volcanic centers including basaltic cinder cones, shield volcanoes, and rhyolitic domes near areas like the Cima Volcanic Field, the Amboy Crater area, and volcanic features in the Victorville to Barstow corridor. Morphologies include spatter cones, scoria cones, pahoehoe and aa lava flows, and lava tubes comparable to features studied at Lava Beds National Monument and in the Cascades Volcanic Arc. Surface expressions are mapped in conjunction with regional landforms such as the Mojave National Preserve, the Anza-Borrego Desert State Park, and near infrastructure corridors like Interstate 15 and Interstate 10.
Eruptive ages span late Pliocene to Holocene, with many centers active in the Pleistocene and a few proposed Holocene events comparable to young eruptions documented at Parícutin and inferred from radiocarbon-dated charcoal and paleosols at sites studied by teams from Arizona State University and University of Arizona. Chronologies derive from radiometric methods including K–Ar dating, Ar–Ar dating, and radiocarbon dating applied by laboratories at USGS Menlo Park and university geochronology centers. Correlations with regional climate records from Lake Cahuilla and paleoseismic records along the San Andreas Fault inform temporal patterns of eruption and repose.
Rock types range from alkali basalts and basanites to transitional tholeiites and silicic products such as dacite and rhyolite; mineral assemblages include olivine, clinopyroxene, plagioclase, and accessory magnetite and ilmenite. Geochemical trends reflect mantle source heterogeneity, fractional crystallization, and crustal assimilation analogous to processes invoked for the Basin and Range Province and the Transverse Ranges. Isotopic studies using Sr–Nd–Pb systems conducted by researchers at California Institute of Technology, Scripps Institution of Oceanography, and University of California, Davis indicate mixture of depleted mantle components and enriched lithospheric signatures similar to those reported for parts of the Mexican Volcanic Belt.
Seismic tomography, gravity surveys, and magnetotelluric profiles from programs led by USGS, Scripps Institution of Oceanography, and Caltech Seismological Laboratory have imaged low-velocity zones and crustal anomalies beneath volcanic centers, suggesting partial melts or enhanced heat flow beneath transtensional regions like the Salton Trough. Remote sensing using Landsat, ASTER, InSAR, and airborne radiometric surveys have mapped lava flow extents, thermal anomalies, and deformation; these datasets are integrated with digital elevation models from USGS National Map and Shuttle Radar Topography Mission to quantify vent alignments and structural controls, paralleling approaches used for the Yellowstone volcanic field and Hawaii Volcanoes National Park.
Hazard analyses consider potential for low-to-moderate severity basaltic eruptions, lava flow emplacement, and volcanic gas release, evaluated relative to population centers such as Los Angeles, Riverside County, and San Bernardino County and critical infrastructure including Interstate 10, Interstate 15, and State Route 78. Assessments draw on probabilistic models used by USGS Volcano Hazards Program and emergency planning frameworks employed by Federal Emergency Management Agency and state offices like the California Governor's Office of Emergency Services. Secondary hazards include ash dispersal affecting airports such as Los Angeles International Airport, groundwater contamination in basins like the Coachella Valley, and induced seismicity along nearby faults including the Garlock Fault.
Indigenous peoples including groups associated with the Mojave, Cahuilla, Luiseño, and Tongva territories lived with volcanic landscapes and incorporated volcanic stones into tools and trade networks documented by archaeologists at institutions such as Smithsonian Institution, University of California, Riverside, and San Diego Museum of Man. Historic-era features were surveyed during expeditions such as the U.S. Army Corps of Topographical Engineers reports and later by geological surveys during the era of John Muir-era exploration. Contemporary conservation and recreation occur within protected areas managed by agencies including the National Park Service, Bureau of Land Management, and California Department of Parks and Recreation.
Category:Volcanism of California