The St. George basin geothermal area covers roughly 250 mi 2 (650 km2) in extreme southwestern Utah and includes the Santa Clara and Virgin River Valleys in Washington County. The Pine Valley Mountains to the north, the Beaver Dam Mountains to the west, the Hurricane Cliffs to the east, and the Utah-Arizona state line to the south border of the basin. The basin lies along the western margin of the Colorado Plateau, just east and south of the Basin and Range - Colorado Plateau Transition Zone