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The Geothermal Map of California

Susan F. Hodgson

The Geothermal Map of California is the most comprehensive map made of the state’s geothermal resources. Released in October 2002 by the California Department of Conservation’s Division of Oil, Gas and Geothermal Resources and the California Geological Survey, the map is drawn at a scale of 1:1,500,000 and was digitally produced with a PC-based geographic information system. It includes digital layers of geothermal field boundaries, sites of power plants and other commercial geothermal projects, low- and high-temperature wells, and thermal springs.

For many years, four major institutions have been gathering geo-thermal information about the state. Now for the first time, all the data are brought
together: boundaries of Known Geothermal Resource Areas from the U.S. Bureau of Land Management; commercial, low-temperature geothermal projects from the Geo-Heat Center of the Oregon Institute of Technology; thermal springs and low-temperature geothermal wells from the California Geological Survey; and geothermal fields, power plants, high-temperature production wells, and plugged and abandoned wells from the California Division of Oil, Gas and Geothermal Resources.

The map is designed for energy planners, geothermal developers, resource managers and everyone who is curious about California’s geothermal resources. Because the map is so complete, people can see at a glance where the state’s geothermal features are located and where they stand in relation to each other.

For example, while California’s best-known volcanoes — Mount Shasta and Mount Lassen — are both in the northernmost part of the state, California’s geothermal resources, both commercial and undeveloped, are concentrated in the border areas surrounding the central Great Valley, and most areas of the state are devoid of any geothermal features at all. Except for the thermal springs, the geothermal features on the map are clustered to such an extent that only five inset maps and an additional small map of California are needed to illustrate them all. The shaded relief map overlying the large state map shows where the geothermal areas lie in respect to the mountain ranges and valleys.

Highlights of the map are:

To order the Geothermal Map of California, contact the California Department of Conservation, Division of Oil, Gas and Geothermal Resources, at 801 K Street, MS 20-20, Sacramento, CA 95814-3530. Phone: 916/445-9686, or online. The map is available for $3, flat or folded, including shipping and handling.

A related map, the Energy Map of California, drawn at a scale of 1:1,000,000, may be purchased flat or folded for $5, including shipping and handling. Geothermal in California, a booklet about geothermal resources and geothermal development prepared for students in grades eight through 12, is available free of charge.

Hodgson is publications supervisor for the California Division of Oil, Gas, and Geothermal Resources. She writes about geothermal resources and development around the world. E-mail:

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