Images

Some of the 24 overlapping lava domes that make up Mammoth Mountain are visible in this 3D geologic map. Many of the domes are made of dacite ("dsd", "dwr") and rhyolite lava ("rss", "rsq"), and are surrounded by smooth surface deposits of pumice and sedimentary material. 

The eddy covariance station shown in this photo has been continuously measuring CO₂ emissions since 2014, providing half-hourly measurements of volcanic gas flux. Unlike previous seasonal monitoring that was limited by snowpack, this 6-meter-tall tower setup with commercial power allows year-round operation - a first for volcanic gas monitoring in this environment.

View of the Mammoth Mountain lava dome complex overlooking Horseshoe Lake.

Photograph of permanent eddy covariance station installed since 2014 in area of volcanic CO₂ emissions on Mammoth Mountain, California. USGS photo by Jennifer Lewicki, August 2019.

Main hydrothermal features of the new (2016) 3-D model of the subsurface at Long Valley Caldera. This schematic is based on a survey of the electrical properties of the earth (magnetotellurics) below. Arrows show subsurface water flow, with colors keyed to changing water temperature, from blue (cold) to red (hot). Purple arrows show an extinct hot water pathway.

Volcanic-gas "sniffer" installed at Mammoth Mountain, California measures temperature plus carbon dioxide and other gas concentration from a steaming vent.

Carbon dioxide gas detection instrument installed at Horseshoe Lake, Mammoth Mountain, California.

Hydrothermal system and water flow in the subsurface beneath Long Valley Caldera, California. Cartoon Illustration from USGS FS 2007-3045.

Map of volcanic ashfall. Areas of the United States that once were covered by volcanic ash from Yellowstone's giant eruptions 2 million and 630,000 years ago, compared with ashfall from the 760,000-year-old Long Valley caldera eruptions at Mammoth Lakes, California, and the 1980 eruption of Mount St. Helens, Washington.

An aerial view looking south of the Long Valley volcanic region in the area of Mono Lake, showing a line of rhyolite lava domes and explosion craters. An inset map shows the locations of silcic magmatic centers in the Long Valley area.