Assessment of geothermal resources of the United States: 1978

The geothermal resource assessment presented in this Circular is a refinement and updating of USGS Circular 726. Nonproprietary information available in June 1978 is used to assess geothermal energy in the ground and, when possible, to evaluate the fraction that might be recovered at the surface. Five categories of geothermal energy are discussed:

a. Conduction-dominated regimes

b. Igneous-related geothermal systems

c. High-temperature (>1500C) and intermediate-temperature (90°-150°C) hydrothermal convection systems

d. Low-temperature (