Geothermal Features

Geothermal features are surface manifestations of the internal heat of Earth interacting with groundwater. Earth's internal heat developed during the early evolution of the planet, and additional heat is generated by the decay of radioactive elements, primarily uranium, thorium, and potassium. However, the most important heat source is shallow magma bodies and associated volcanic activity.

Geothermal areas can be classified into high temperature and low temperature, based either directly on subsurface water temperatures or indirectly on the geological settings. High-temperature geothermal areas have water temperatures in the uppermost 1,000 m (meters) of greater than 200°C. Low-temperature geothermal areas are characterized by water temperatures ranging from close to 20 to 150°C and can be found in formerly active volcanic regions, on the margins of [Page 1271]active volcanic ...