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Geothermal energy

Geothermal Energy

Geothermal energy comes from steam (or hot water that has been converted to steam) from deep inside the earth. The word geothermal comes from the Greek words geo for earth, and therme for heat. So geothermal means "earth heat."

Our planet's interior is very hot—at its core, 4,000 miles deep, temperatures may reach over 9,000°F. This heat is continuously conducted from the earth's core to the surrounding layer of rock, the mantle.

There are some places around the earth where magma (hot molten earth from the mantle) pushes up through cracks into the crust near the earth's surface. Magma can heat nearby rock and water as hot as 700°F. Some of this hot water reaches the earth's surface as hot springs or geysers, and some stays trapped deep underground in cracks and porous rocks. This hot water can be used directly or converted into steam to turn turbines that generate electricity at geothermal power plants.


Besides hot spring bathing, heating of individual buildings and of entire cities is the oldest and most common direct use of natural hot water. In Klamath Falls, Oregon, which has one of the largest city geothermal heating systems in the United States, geothermal water is also piped under roads and sidewalks to keep them from icing over in freezing weather. The city could not afford to use any other method to keep hot water running continuously through cold pipes!