Compositional data on gases collected at fumaroles, hot springs, and gas vents across the Long Valley Caldera, California, 1994 – 2020

The Long Valley Caldera in eastern California formed about 760,000 years ago following the eruption of ~600 km3 of high-silica rhyolite. The Long Valley volcanic-hydrothermal system contains sufficient heat to support the Casa Diablo binary geothermal power plant sited on the margin of the resurgent dome. Present day volcanic activity is evidenced by periods of seismicity and deformation and the presence of magmatic volatiles in thermal fluids. The U.S. Geological Survey (USGS) uses a variety of techniques to monitor the volcanic system that underlies the Long Valley Caldera. Monitoring data include measurements of seismicity and deformation and chemical analyses of thermal waters and gases that are emitted at hot springs, fumaroles [...]