When the planet was first formed, it was a fiery ball of liquid and gas. As it cooled, an outer crust formed over the hot mass. This crust is the surface of the earth where man dwells.
Geothermal energy is nearly as old as the Earth itself.
It comes from heat being trapped in hot melted rock, called magma or lava, below the Earth's surface. When this heat energy is tapped, it is a tremendous source of power. When rainwater seeps through cracks in the Earth's crust, it is heated by magma and turns to steam. The steam rises to the atmosphere, cools, turns back to liquid, falls back to earth as rain and eventually seeps back through cracks to be turned back into steam. Arizona has an abundance of low-temperature geothermal areas, or hot springs, in the southeastern part of the state.