Geothermal energy is clean and plentiful, but up until now, it has mostly been restricted in the U.S. to the western part of the country because of the unique geologic qualities of the region. Namely, the ground is a lot hotter there. But advances in geothermal drilling techniques mean that the country is no longer beholden to old ideas about the temperature thresholds of geothermal; we can now make heat from areas where the drills reach temperatures as low 212 degrees Fahrenheit, which opens up areas across the U.S.
This Google Earth map from SMU’s Geothermal Laboratory, funded by a Google.org grant, details the country's geothermal resources based on the availability of advanced drilling techniques. The conclusion: The U.S. can produce over three million megawatts of geothermal energy, or 10 times the capacity of currently installed coal power plants.
The map reveals a number of untapped geothermal resources, including Western Pennsylvania, West Virginia, northern Louisiana, South Dakota, and southeastern Colorado. In West Virginia alone, there is a geothermal treasure trove that rivals the state's current coal-based power supply.
Of course, just because we can drill in all these places doesn't mean we should. Geothermal drilling can induce seismicity in some areas--so it's possible that drilling can cause earthquakes.
Regardless of whether drilling poses any real seismic danger, there will probably be plenty of NIMBYs protesting future developments--not that the majority of our other energy-producing technologies are much safer.