Publications Details

Science guide for the Long Valley Caldera deep hole

Rundle, J.B.

The Magma Energy Program of the US Department of Energy, Geothermal Technology Division, is planning to begin drilling a deep (6 km) exploration well in Long Valley Caldera, California, in September 1988. The location of the well is in the central part of the caldera, coincident with a large number of shallow (5-7 km) geophysical anomalies identified through many independent investigations. Results from the hole will permit the following: direct investigation of the geophysical anomalies interpreted to be magma; investigation of the patterns and conditions of deep fluid circulation and heat transport below the caldera floor; determination of the amount of collapse and subsequent resurgence of the central portion of Long Valley caldera; and determination of the intrusion history of the central plutonic complex beneath the caldera, and establishment of the relationship of intrusive to eruptive events. The hole will thus provide a stringent test of the hypothesis that magma is still present within the central plutonic complex. If the interpretation of geophysical anomalies is confirmed, the hole will provide the first observations of the environment near a large silicic magma chamber. 80 refs., 7 figs., 2 tabs.