Geothermal power is a great idea as an efficiency measure when closed loops of piping are used to preheat or precool air or water. This can be done anywhere and helps minimize the use of electricity or heating fuels for heating and cooling of building temperatures or the heating of water.
However, when geothermal is used to produce electricity (which, in the U.S., is only possible in western states), these larger systems are all "open-loop" types that suck water out of the ground. These can actually deplete the resource. Open loop geothermal is not clean, as communities are exposed to emissions of hydrogen sulfide, ammonia, carbon dioxide and radon. Also, there are notable environmental justice issues around geothermal proposals in Hawaii and in parts of California, where communities of color have been threatened with damaging geothermal development.
Geothermal in Hawaii:
"During operation of the geothermal wells, gases may be released to the atmosphere. These gases include carbon dioxide, hydrogen sulfide, ammonia, and trace amounts of radon-222. The emission of hydrogen sulfide gas is considered to be the most important public health problem related to the operation of these geothermal wells. Since hydrogen sulfide is heavier than air, it can accumulate in low-lying areas during temperature inversions or when prevailing trade winds are calm."
Geothermal in California:
Geothermal in Nevada:
The good kind of geothermal... the kind you can use anywhere: Geothermal heat pumps