Geothermal

Geothermal energy (from the Greek roots geo, meaning earth, and therm, meaning heat) refers to energy in the form of natural heat flowing outward from within the Earth and contained in rocks, water, brines, or steam. This heat is produced mainly by the decay of naturally occurring radioactive isotopes of thorium, potassium, and uranium in the Earth's core. Geothermal energy can be used for electricity production, for direct use purposes, and for home heating via geothermal heat pumps.