4. Geothermal Energy

Geysers can be used as an energy source, tapping into Earth's geothermal heat. Photo courtesy of CK-12. 

Geothermal energy comes from heat deep below the surface of the Earth. That heat may come to the surface naturally or it may be available through drilling. Nothing must be done to the geothermal energy. It is a resource that can be used without processing.

The heat that is used for geothermal power may come to the surface naturally as hot springs or geysers, like The Geysers in northern California. Where water does not naturally come to the surface, engineers may pump cool water into the ground. The water is heated by the hot rock and then pumped back to the surface for use. The hot water or steam from a geothermal well spins a turbine to make electricity.

Geothermal energy is clean and safe. The energy source is renewable since hot rock is found everywhere in the Earth, although in many parts of the world the hot rock is not close enough to the surface for building geothermal power plants. 

Geothermal power plant in Iceland. Photo coutesy of CK-12. 

Source: Geothermal Power. Retrieved frmo http://www.ck12.org/book/CK-12-Earth-Science-Concepts-For-High-School/r16/section/12.14/ on August 27, 2013.