Hydrothermal Energy Resources (Illustrated GIF)

Conventional hydrothermal resources occur below the ground where three ingredients combine: heat, water and permeable rock. When heated water or steam is trapped in a porous rock below a layer of less permeable rock, a hydrothermal reservoir is formed. These reservoirs may be high-temperature (>150 degrees), medium-temperature (90-150 degrees) or low-temperature (<90 degrees). 

High-temperature hydrothermal resources tend to occur near plate boundaries, such as in the Western U.S., and may be associated with hot springs and vents on the Earth’s surface. Medium- and low- temperature hydrothermal resources are more widely distributed. 

This GIF is modified from an illustration by Kimber Petersen in a 2025 Fact Sheet.