A Model of the Hydrothermal System of Long Valley Caldera, California

Abstract

Long Valley caldera, an elliptical depression covering 450 km 2 on the eastern front of the Sierra Nevada in east-central California (Fig. l ), contains a hot-water convection system with numerous hot springs and measured and estimated aquifer temperatures at depth of 18OoC-28O0C. In this study, the results of previous geologic, geophysical, geochemical, and hydrologic investigations of the Long Valley area have been synthesized to develop a generalized conceptual and mathematical model which describes the natural conditions of heat and fluid flow in the hydrothermal system. Because only one deep drill-hole (2 km) has thus far been completed within the caldera, this model must be considered speculative in detail, although its gross features are consistent with known constraints. Details of the work discussed in this summary will be published as a U.S.G.S. open-file report in February, 1977.