Definition of Geothermal Energy

Geothermal energy is heat extracted from the Earth’s interior. The term originates from two Greek roots: the word geo which means “earth” and the word thermos which means “heat.”

How is geothermal energy obtained?
The temperature increases with depth in the Earth, a value called the geothermal gradient. Beneath stable continents the gradient is ordinarily 30°C/km, however, in active tectonic areas it can be as high as 100°C/km. Ground water circulating underground through the hot rocks is heated. Very deep wells can be drilled to access the steam and water from these sources. In some places there is molten rock, called magma, which is extremely hot. Once brought to the surface, the energy can be used as heat or to generate electricity, or to heat buildings. Geothermal energy also can come from shallow ground, although the temperature is the lower.

What is geothermal energy used for?
Geothermal energy is used for electricity generation. It is also used as a form of direct heat.