Unrest at Large Quaternary Silicic Calderas: 
Long Valley caldera (CA)

Landsat Image of the Mono Lake - Long Valley caldera volcanic region. Mono Lake is located in the upper left corner of the image. Long Valley caldera is the oval depression
The ongoing unrest includes recurring earthearthquake swarms and continued dome-shaped uplift of the central section of the caldera (the resurgent dome).

Project Summary Calderas are collapse structures associated with the world's largest volcanic eruptions. Several Quaternary calderas exhibit signs of restlessness, including seismicity and uplift, which may last for decades. The fact that some calderas (e.g., Yellowstone) have subsided without eruption or clear evidence of intrusion into the adjacent crust, has led some to suggest that the uplift and seismicity are caused by perturbations to the calderasí hydrothermal systems rather than to the intrusion of magma. Differentiating between magmatic intrusion on the one hand, and thermal expansion or pressurization of the caldera hydrothermal system on the other, is critical for accurate assessment of volcanic hazards. 

Long Valley caldera, located on the eastern front of the Sierra Nevada range in California, formed by collapse of the roof of the magma chamber during the catastrophic eruption of the Bishop Tuff 0.73 million years ago. Since mid 1980, the caldera has experienced ground uplift and numerous earthquake swarms, prompting the U.S. Geological Survey to issue a "Notice of Potential Volcanic Hazard" for a few months in 1982 and to start an intensive monitoring effort in the area. Modeling of gravity data  suggests inflation of a magma reservoir beneath the caldera. 

Active research: inversion geodetic and gravity data using more realistically distributed geological sources to move beyond the use of single point sources when modeling geodetic data in volcanic areas.

Tools GPS, micro-gravity, GIS, mathematical modeling
Geographic Location Long Valley caldera (CA)
Group Members Involved Maurizio Battaglia [e-mail] [web page]
Michael Manga, Roland Bürgmann
Project Duration Active project (last GPS and micro-gravity survey in 1999).
More Information Papers on Long Valley
Long Valley caldera GIS database