One renewable energy resource that is drawing increasing attention is geothermal. As technology for using geothermal energy improves, the areas that can provide this form of power are expanding.
Researchers at Southern Methodist University, funded by Google, have estimated relative geothermal potential in the US with a new map that is based in part on newer data drawn from oil and gas drilling operations. The results underscore the known good potential in much of the western US, and also note good prospects in parts of the Appalachians (particularly in parts of PA and WV), as well as substantial areas in TX, LA, and MS. Google says the newer geothermal technologies that are being explored in the US and a number of other countries suggest there may be decent geothermal prospects in all 50 states. If the new and old technologies pan out, various experts are saying geothermal could supply a very large percentage of all US energy demand.
- New mapping, SMU press release,  Oct. 25, 2011 (includes map); accompanying report, by David Blackwell and Maria Richards, to be published (date unknown) here. 
- SMU, Geothermal Laboratory ; earlier mapping effort, 2004 Geothermal Map of North America ; Maria Richards,  214-768-1975.
- Google, Enhanced Geothermal Systems  (includes tools to explore the new SMU mapping in Google Earth); FAQs  (touts relatively new methods for tapping geothermal, including techniques that fracture rock and inject fluids, which likely will have some environmental consequences that aren't highlighted by Google); Parag Chokshi,  Clean Energy Public Affairs, 650-383-7075.
For the Bureau of Land Management and US Forest Service perspective on US geothermal prospects (with the focus on the western US), see:
- BLM, Geothermal. 
- TipSheet of Nov. 12, 2008 ; Programmatic EIS , October 2008 (as one starting point, see Volume 1, Chapter 2 for several maps and some detail on general concepts and specific sites).
For other perspectives, see:
To see how US resources mesh with those in Canada, and to possibly gather some additional information about geothermal energy, see the TipSheet of Sept. 28, 2011.