Long Valley Caldera | U.S. Geological Survey Official websites use .gov .gov website belongs to an official government organization in the United States. Secure .gov websites use HTTPS lock ( or means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites. Long Valley Caldera Find U.S. Volcano Filters The map displays volcanoes, earthquakes, monitoring instruments, and past lava flows. Get Help Earthquake Plots To view an earthquake cross-sectional plot, click "Draw Plot" to start drawing on the map. Once the plot area is selected, click on "View Plot" to view chart or "Clear Plot" to start over. Map Layers Earthquake Colors Earthquake Depth Units Earthquake Time Units Results Filters The map displays volcanoes, earthquakes, monitoring instruments, and past lava flows. Get Help Earthquake Plots To view an earthquake cross-sectional plot, click "Draw Plot" to start drawing on the map. Once the plot area is selected, click on "View Plot" to view chart or "Clear Plot" to start over. Settings Map Layers Earthquake Colors Earthquake Depth Units Earthquake Time Units Map Legend Map Legend Results Long Valley Caldera Science Multimedia Publications Maps News Connect 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. A quiet exhalation at Long Valley January 13, 2026 A quiet exhalation at Long Valley Is it just me, or is it quiet? A seismically uneventful year for Long Valley January 6, 2026 Is it just me, or is it quiet? A seismically uneventful year for Long Valley Hazard-ception: Fires are a hazard for monitoring California's hazardous volcanoes November 18, 2025 Hazard-ception: Fires are a hazard for monitoring California's hazardous volcanoes View All February 25, 2019 California’s exposure to volcanic hazards 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... Authors Margaret Mangan, Jessica Ball, Nathan Wood, Jamie L. Jones, Jeff Peters, Nina Abdollahian, Laura Dinitz, Sharon Blankenheim, Johanna Fenton, Cynthia Pridmore By Volcano Hazards Program Volcano Science Center California Volcano Observatory Clear Lake Volcanic Field Coso Volcanic Field Lassen Volcanic Center Long Valley Caldera Mammoth Mountain Medicine Lake Mono Lake Volcanic Field Mono-Inyo Craters Mount Shasta Salton Buttes Soda Lakes Ubehebe Craters October 22, 2018 2018 update to the U.S. Geological Survey national volcanic threat assessment 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... Authors John W. Ewert, Angela K. Diefenbach, David W. Ramsey By Volcano Hazards Program Volcano Science Center Agrigan Ahyi Seamount Alamagan Anatahan Asuncion Belknap Black Butte Crater Lava Field Black Rock Desert Volcanic Field Blue Lake Crater Carrizozo Lava Flow Cascade Range Weekly Update Cinnamon Butte Clear Lake Volcanic Field Coso Volcanic Field Crater Lake Craters of the Moon Volcanic Field Daikoku Seamount Davis Lake Volcanic Field Devils Garden Lava Field Diamond Craters Volcanic Field Dotsero Volcanic Center East Diamante Esmeralda Bank Farallon de Pajaros Fukujin Seamount Glacier Peak Guguan Haleakalā Hell's Half Acre Lava Field Hualālai Indian Heaven Volcanic Field Jordan Craters Volcanic Field Kama‘ehuakanaloa Kasuga 2 Kīlauea Lassen Volcanic Center Long Valley Caldera Mammoth Mountain Markagunt Plateau Volcanic Field Maug Islands Mauna Kea Mauna Loa Medicine Lake Mono Lake Volcanic Field Mono-Inyo Craters Mount Adams Mount Bachelor Mount Baker Mount Hood Mount Jefferson Mount Rainier Mount Shasta Mount St. Helens Newberry Ofu-Olosega Pagan Red Hill-Quemado Volcanic Field Ruby Salton Buttes San Francisco Volcanic Field Sand Mountain Volcanic Field Sarigan Soda Lakes South Sarigan Seamount Supply Reef Ta'u Island Three Sisters Tutuila Island Ubehebe Craters Uinkaret Volcanic Field Valles Caldera Wapi Lava Field Weekly Update West Crater Volcanic Field Yellowstone Zealandia Bank Zuni-Bandera Volcanic Field December 10, 2014 The California Volcano Observatory: Monitoring the state's restless volcanoes 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... Authors Wendy K. Stovall, Mae Marcaida, Margaret T. Mangan By Natural Hazards Mission Area Volcano Hazards Program Volcano Science Center Clear Lake Volcanic Field Coso Volcanic Field Lassen Volcanic Center Long Valley Caldera Mammoth Mountain Mono Lake Volcanic Field Mono-Inyo Craters Mount Shasta Salton Buttes Soda Lakes Ubehebe Craters View All November 20, 2023 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. By California Volcano Observatory Long Valley Caldera Long Valley Caldera Field Guide November 20, 2023 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. November 19, 2023 Vertical columns of volcanic rock at Devils Postpile National Monument A spectacular display of a columnar-jointed basalt flow. By California Volcano Observatory Long Valley Caldera Vertical columns of volcanic rock at Devils Postpile National Monument November 19, 2023 Vertical columns of volcanic rock at Devils Postpile National Monument A spectacular display of a columnar-jointed basalt flow. November 18, 2023 Long Valley Caldera Field Guide - Glass Creek Flow Example of two magmas that mixed during an eruption. By California Volcano Observatory Long Valley Caldera Long Valley Caldera Field Guide - Glass Creek Flow November 18, 2023 Long Valley Caldera Field Guide - Glass Creek Flow Example of two magmas that mixed during an eruption. View All 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 Volcanoes Hazards Program Links Assess Prepare Forecast Activity Products Observatories About Was this page helpful?