Geothermal heat map of US hot springs

Every hot spring on this site, plotted over a map of the heat rising through the ground. The warm colors mark where heat from deep in the earth reaches the surface fastest, and the springs crowd into them.

Tap a pin for the spring's water temperature and heat flow. Alaska and Hawaii springs are on the map without a heat flow value.

Heat flow measures how much warmth works its way up from deep inside the earth, in milliwatts per square meter. Across the United States it averages about 65.

Most of the West runs well above that. The crust there has been stretched thin and broken by faults, which leaves hot rock closer to the surface. Rain and snowmelt sink down through those cracks and come back up hot.