A picture is worth a thousand words—USGS Post Doctoral Fellow Jared Peacock's new 3D geophysical model for the Long Valley Caldera and Mammoth Mountain reveals a subsurface marked by active hydrothermal reservoirs (hot water and fluids), bodies of partial melt (molten rock), and rock that has been pervasively altered to clay by fluids from a now extinct hydrothermal reservoir.
What's Under Long Valley? Water, Heat, and Molten Rock!
Using magnetotelluric (MT) data, Jared located a robust hydrothermal reservoir with a source located about 4 km (2 and a half miles) under Deer Mountain. Groundwater heated in this reservoir flows upward and eastward towards the caldera's Resurgent Dome. A separate hydrothermal reservoir was identified under Mammoth Mountain at a depth of about 1 km (0.6 mi). Both reservoirs are fueled by heat emanating from small bodies of partially molten rock located more than 8 km (5 mi) below the surface. The new model verifies and improves upon the results of earlier geophysical investigations.