geothermal flux

Heat from the earth's interior generated by early gravitational collapse, and later radioactive decay. Geothermal energy may be extracted by pumping water down through an injection well and forcing it through joints in the hot rocks. When the water returns to the surface it may be converted to steam, for use in a generator, or run through a heat exchanger. This is potentially an important energy source in any volcanically active area, and is used in Iceland and New Zealand.