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Long Valley Exploratory Well



Long Valley Drill RigA scientific drilling effort has been proposed to deepen an existing 2-km deep hole to a target depth of between 3.5 and 4.0 km. The borehole is located near the center of the resurgent dome of Long Valley Caldera in east-central California. Deepening the well has been accomplished by continuous H-size coring (2.5" diameter core) to the target depth. The ICDP with 80% matching funds from the California Energy Commission (CEC), the U.S. Department of Energy (DoE), and the U.S. Geological Survey (USGS) supported the project. Long Valley Caldera has shown sustained unrest since 1980 characterized by recurring earthquake swarms, inflation (dome-shaped uplift) of the resurgent dome, and increased levels of fumarolic activity accompanied by high concentrations of carbon dioxide (CO2) gas in the soils around Mammoth Mountain on the southwest margin of the caldera. The existing 2-km-deep hole is located directly over the center of inflation in the resurgent dome (total uplift since 1979 is 60 cm and the current uplift rate is 2-3 cm/y) and at the northern margin of the earthquake swarm activity.    

Scientific goals of the proposed drilling were to shed light on the nature of processes at mid-crustal depths in areas of active deformation by

  • drilling into the seismogenic volume beneath the resurgent dome and
  • obtaining a complete core section for studies of the petrology, fracture state, and pore fluids,
  • determining the temperature profile below the hydrologic convective regime that appears to control temperature shallower than 2 km,
  • determining the state of stress within the seismogenic volume, and
  • modeling present-day hydrothermal conditions.

In the long term, the hole is being used as a geophysical observatory with a number of down-hole instrument packages to track processes occurring directly above the inflating magma chamber driving unrest in the caldera.

(Photo ©:ICDP)



North America, U.S.A., United States of America, California, Sierra Nevada, Long Valley Caldera



37° 40' 47'' N, 118° 54' 31'' W (Please scroll down to end of page for more information.)


Project Start and End
  • Begin of drilling June 15, 1998
  • End of drilling September 15, 1998


Programs and Funding


Principal Investigators
  • David P. Hill, U.S. Geological Survey at Sacramento
  • John Sass, U.S. Geological Survey at Flagstaff
  • John Traver Finger, Sandia National Laboratories


Cooperating Principal Investigators
  • Roy A. Bailey, U.S. Geological Survey at Sacramento
  • Christoph Clauser, RWTH Aachen University, E.ON Energy Research Center, Applied Geophysics and Geothermal Energy
  • John C. Eichelberger, U.S. Geological Survey at Reston, Volcano Hazards Program
  • John C. Eichelberger, University of Alaska at Fairbanks, Graduate School
  • William L. Ellsworth, U.S. Geological Survey at Menlo Park, Earthquake Hazards Program, Northern California
  • Christopher D. Farrar, U.S. Geological Survey at Sacramento
  • Stephen Hoyt Hickman, U.S. Geological Survey at Menlo Park, Earthquake Hazards Program, Northern California
  • Paul Kasameyer, Lawrence Livermore National Laboratory, Earth Science Division
  • Vicki Sue McConnell, Geological Society of America
  • Michael L. Sorey, U.S. Geological Survey at Sacramento
  • John W. Valley, University of Wisconsin at Madison, Department of Geoscience, Geophysics
  • Daniel F.C. Yang, Borealis Geopower
  • Mark D. Zoback, Stanford University, School of Earth Sciences, Department of Geophysics


Partners and Contractors



Caldera, California, Drilling, ICDP-1997/13, Long Valley, LVEW, Thermal Regimes, U.S.A., Volcanic Systems


Current State



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