Young and Old Volcanoes in Eastern California: New Map, Report and Public Events

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The map includes the Long Valley Caldera, Mono-Inyo chain, Mammoth Mountain and the Middle Fork canyon of the San Joaquin River, including Devils Postpile National Monument.

Geophysical unrest beneath the Mammoth Mountain volcano, and in adjacent parts of the Sierra Nevada and Long Valley Caldera, has generated some concern among residents, stakeholders, and geoscientists since at least 1980 when four magnitude-6 earthquakes shook the area. Three decades of volcano monitoring near Mammoth Mountain has documented numerous earthquake swarms, ground deformation, and emission of magmatic carbon dioxide gas . The new map and publication contribute detailed information to scientists' understanding of the eruption frequency and volcanic history of the area, which is essential for assessing the region's likely long-term future volcanic activity.

The new map and report represent a significant milestone after decades of geologic fieldwork and research. The release of the map and report coincides with the 2016 celebration of the 100th anniversary of the establishment of the National Park Service. In the month of July, staff from the USGS, Devils Postpile National Monument and Inyo National Forest have teamed up to offer outdoor educational activities for the public as the new map and report are unveiled. CalVO geologists Wes Hildreth, Judy Fierstein, and others will be hosting an interpretive talk at Minaret Vista Overlook near the monument on July 14. They will also lead an interpretive hike to the Devils Postpile formation and to nearby Rainbow Falls, both in the monument, on July 15. If you plan to visit Devils Postpile National Monument this week, be sure to check out these great opportunities to hear about the volcanic history of the area from expert geologists!