Geothermal Energy

Geothermal energy is the heat contained within Earth that generates geological phenomena on a planetary scale. The term geothermal energy is often used to indicate that part of Earth's heat that can, or could, be recovered and exploited by humans. The presence of volcanoes, hot springs, and other thermal phenomena clearly demonstrates that the interior of Earth is hot: Earth's temperature increases with depth.

This heat is continually generated by the decay of the long-lived radioactive isotopes of uranium (238U, 235U), thorium (232Th), and potassium (40K), which are present in Earth, in addition to the primordial energy of planetary accretion. The total heat content of the crust of Earth can be estimated in the order of 5.4 × 1021 MJ (mega-joules). As a comparison, the ...