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Long Valley Caldera

Find U.S. Volcano

The 16 x 32 km (20 x 10 mi) Long Valley caldera east of the central Sierra Nevada Range formed as a result of the voluminous Bishop Tuff eruption (considered a "supereruption") about 760,000 years ago.

Quick Facts

Location: California, Mono County
Latitude: 37.7° N
Longitude: 118.87° W
Elevation: 2,600 (m) 8,530 (f)
Volcano type: caldera
Composition: basalt to rhyolite
Most recent eruption: 16,000-17,000 years ago
Nearby towns: Mammoth Lakes
Threat Potential: Very High*

*based on the National Volcano Early Warning System

Summary

Resurgent doming in the central part of the caldera occurred shortly after the caldera-forming eruption. During early resurgent doming, the caldera was filled with a large lake that left lake-shore traces (strandlines) on the caldera walls and the resurgent dome peninsula; the lake eventually drained through the Owens River Gorge.

Along the caldera's ring fault, Mammoth Knolls is the youngest eruption about 100,000 years ago. In the topographic basin, Cone 2652 in West Moat is about 33,000 years old and dacite lavas in NW Moat are 40,000-27,000 years old. The mafic chain along the west rim is 16,000 to 17,000 years old. The caldera remains thermally active, with many hot springs and fumaroles, and has had significant deformation, seismicity, and other unrest in recent years. A robust geothermal system inside the caldera fuels the Casa Diablo power plant, which generates enough power for 40,000 homes. 

The late-Pleistocene to Holocene Mono-Inyo Craters, which cut the northwest topographic rim of the caldera, along with Mammoth Mountain, on the southwest topographic rim, is west of the structural caldera and are chemically and tectonically distinct from the Long Valley magmatic system. The most recent activity in the area was about 300 years ago in Mono Lake. Both Long Valley Caldera and Mammoth Mountain have experienced episodes of heightened unrest over the last few decades (earthquakes, ground uplift, and/or volcanic gas emissions). As a result, the USGS manages a dense array of field sensors providing the real-time data needed to track unrest and assess hazards.

News

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When it comes to calderas, how big is big?

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Getting sphere-ious about spherulites

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USGS volcano scientists visit Long Valley

Publications

California’s exposure to volcanic hazards

The potential for damaging earthquakes, landslides, floods, tsunamis, and wildfires is widely recognized in California. The same cannot be said for volcanic eruptions, despite the fact that they occur in the state about as frequently as the largest earthquakes on the San Andreas Fault. At least ten eruptions have taken place in the past 1,000 years, and future volcanic eruptions are inevitable.The

Authors
Margaret Mangan, Jessica Ball, Nathan Wood, Jamie L. Jones, Jeff Peters, Nina Abdollahian, Laura Dinitz, Sharon Blankenheim, Johanna Fenton, Cynthia Pridmore

2018 update to the U.S. Geological Survey national volcanic threat assessment

When erupting, all volcanoes pose a degree of risk to people and infrastructure, however, the risks are not equivalent from one volcano to another because of differences in eruptive style and geographic location. Assessing the relative threats posed by U.S. volcanoes identifies which volcanoes warrant the greatest risk-mitigation efforts by the U.S. Geological Survey and its partners. This update

Authors
John W. Ewert, Angela K. Diefenbach, David W. Ramsey

The California Volcano Observatory: Monitoring the state's restless volcanoes

Volcanic eruptions happen in the State of California about as frequently as the largest earthquakes on the San Andreas Fault Zone. At least 10 eruptions have taken place in California in the past 1,000 years—most recently at Lassen Peak in Lassen Volcanic National Park (1914 to 1917) in the northern part of the State—and future volcanic eruptions are inevitable. The U.S. Geological Survey Californ

Authors
Wendy K. Stovall, Mae Marcaida, Margaret T. Mangan

Science

Long Valley Caldera Field Guide

Ten stops were chosen from published scientific field guides and from California Volcano Observatory field trip notes to represent the geology of the area.
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Long Valley Caldera Field Guide

Ten stops were chosen from published scientific field guides and from California Volcano Observatory field trip notes to represent the geology of the area.
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Vertical columns of volcanic rock at Devils Postpile National Monument

A spectacular display of a columnar-jointed basalt flow.
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Long Valley Caldera Field Guide - Glass Creek Flow

Example of two magmas that mixed during an eruption.
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Long Valley Caldera Field Guide - Glass Creek Flow

Example of two magmas that mixed during an eruption.
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