A story in today's Arizona Daily Sun in Flagstaff quotes USGS geothermal expert Wendell Duffield as calling the area near Sunset Crater as the greatest potential geothermal energy source in the state. Duffield suggests an 8,000' - 10,000' deep well to test below the Coconino Sandstone which serves as a regional aquifer. He describes the aquifer as responsible for depriving the region of telltale hot springs or steam vents by carrying the heat laterally many miles away to places like Verde hot springs.
Yet, the BLM's regional assessment of areas with the highest potential for geothermal energy, completed ignored the San Francisco Volcanic Field and other promising locales. This may make it harder for companies to explore federal lands in the area because they are not included in the BLM planning.
[right, digital elevation model of the 600+ vents in the San Francisco volcanic field that have erupted during the past 6 million years. Credit, USGS]
Sunset Crater, the youngest in the state, erupted around 1064 A.D.