Andrew Steinitz at the World Almanac discusses an "MIT report, which suggests that geothermal energy could commercially supply 10% of the United States’ electrical supply by 2050. Geothermal energy doesn’t seem to get a whole lot of attention; according to MIT, the last in-depth study was done in 1979. This energy traditionally comes from hot springs near the Earth’s surface (like in Reykjavik, Iceland). They emit hot steam, which spins turbines to generate electricity. In contrast to coal, a non-renewable fossil fuel that generates half of the U.S. electrical supply, geothermal energy creates very few emissions; and unlike other "alternative" energy forms, geothermal energy generators can run non-stop without relying on sunlight or wind."