Humans have been enjoying water heated by the Earth for millenia. Bath, England, for example, got its name from the hot springs savored by relaxing Romans.
Nowadays, geothermal power plants also take advantage of water heated by the Earth's interior to boil water into steam. The steam then turns a turbine to make energy. Geothermal is cheap to operate, less expensive to build than nuclear and produces significantly less pollution than fossil fuels.
However, the need for accessible underground heat limited the technology to places like California, the Philippines, El Salvador and Iceland. But new technologies and maps of the Earth's crust are making geothermal a renewable energy competitor to fossil fuels, even in places like coal-rich West Virginia.
In fact, a recent study suggested the United States, already the world's top geothermal energy producer according to the Geothermal Energy Association, may have geothermal resources under its feet capable of producing 10 times the capacity of all coal plants now installed.
Want proof? Google it. The geothermal maps are available on Google Earth, which also helped fund the project.