A hot spring is a place where warm or hot water (significantly warmer than ambient ground temperature, usually around 55-57 degrees in the eastern United States) issues from the ground on a regular basis for at least a predictable part of the year. The water is heated by geothermal heat, or heat generated from the interior of the Earth. This occurs in various "hot spots", where magma or other mantle material is close to the surface. If the water becomes so heated that it builds steam pressure and erupts in a jet above the surface of the Earth, it is termed a geyser.
At least two United States national parks feature hot springs: