Hot dry rock resources occur at depths of 3 to 5 miles (5–8 km) everywhere beneath the Earth's surface and at lesser depths in certain areas. Access to these resources involves injecting cold water down one well, circulating it through hot fractured rocks, and drawing off the heated water from another well. Currently, nobody uses this method commercially. Existing technology also does not yet allow recovery of heat directly from magma, the very deep and most powerful resource of geothermal energy. 