Iceland is not a country that one would normally expect to be powered by its own heat. But it is. Though it's a lot closer to the North Pole than to the equator, it straddles the Mid-Atlantic Ridge, a mostly underwater mountain range that separates the North American and Eurasian tectonic plates. At such boundaries, cracks can form in the earth's crust, allowing magma that's normally hundreds of miles down to bubble up, causing geysers, hot springs, and the occasional volcano.

In the 1970s, Icelanders recognized that this heat was actually a useful form of energy and began using it to warm homes and generate electricity. "Geothermal" power (geo meaning earth, thermal meaning heat) now supplies a fourth of the country's electricity (the rest comes from hydropower). Most of its buildings are heated with geothermal water, and (envious New Yorkers take note) many Reykjavik sidewalks are heated in winter. Most of its outdoor swimming pools are filled with warm geothermal water, making them comfortable year-round. And since geothermal is almost completely nonpolluting, Reykjavik is now one of the world's cleanest cities.

Not only is geothermal electricity power clean, it's so inexpensive in Iceland that local companies now import bauxite from the Caribbean and refine it into aluminum, a highly energy-intensive process. This combination of cheap power and new industry has transformed Iceland from a poor country into a rich one with the confidence to push the energy envelope. In the coming decade, it plans to use geothermal electricity to make hydrogen to run fuel cells its cars and fishing boats, thus becoming the first country to be completely powered by renewable energy sources.

Wow. If only we all sat on tectonic boundaries, the energy crisis would end in a puff of volcanic steam. Well...as it turns out, a lot of places sit on such boundaries and could, with the right expertise, tap just as much geothermal power as Iceland. And new geothermal technologies now make it possible not only to exploit existing hot springs but also to access and use the earth's heat from pretty much anywhere. As for how much energy this could make available, estimates range from merely huge to completely off the charts. A recent study from the Massachusetts Institute of Technology (MIT) concluded that available geothermal power is several million times greater than current worldwide energy demand.

Learn how geothermal works