Since the 1920s The Geysers geothermal power plant 72 miles (115 kilometers) north of San Francisco has been pumping out electricity harvested from hot rocks deep within Earth's crust. But there are only so many natural volcanic formations to be tapped. In locations that are not blessed by easy access to this natural resource, drilling into the hot rock bed and pumping fluid through it has the potential to unleash 2,000 times the total annual consumption of energy in the U.S., according to a 2007 report from the Massachusetts Institute of Technology.

The 1.5-megawatt geothermal power plant at Soultz-sous-Forêts in France is an attempt to deliver on that promise in Europe.

Slide Show: Man-Made Geothermal Power

Companies in Australia like Geodynamics are nearing completion of similar systems, and even Google has invested in developing the technology here in the U.S. After all, for just $1 billion over the next 40 years, the U.S. could develop 100 gigawatts of geothermal electricity generation, which pumps out power 24/7 and emits almost no greenhouse gases or other air pollution.