Tapping the Earth's natural heat

T he Earth is a bountiful source of heat. It continuously produces heat at depth, primarily by the decay of naturally radioactive chemical elements (principally uranium, thorium, and potassium) that occur in small amounts in all rocks. This deep heat then rises toward the cooler surface, where scientists can measure the rate of its escape through the Earth's crust. The annual heat loss from the Earth is enormous equivalent to 10 times the annual energy consumption of the United States and more than that needed to power all nations of the world, if it could be fully harnessed! Even if only 1 percent of the thermal energy contained within the uppermost 10 kilometers of our planet could be tapped, this amount would be 500 times that contained in all oil and gas resources of the world. The Earth's natural heat is cleaner than conventional sources of energy (coal, oil, and gas), and there is less environmental impact associated with its use.