As used in sections 66-1101 to 66-1106, unless the context otherwise requires:

(1) Geothermal resources shall mean (a) the natural heat of the earth and the energy produced by that heat, including pressure, and (b) the material medium containing that energy;

(2) Geothermal fluids shall mean the naturally present ground water in geothermal occurrences;

(3) Geothermal occurrence shall mean an underground geologic formation at temperatures higher than the normal gradient; and

(4) Material medium shall mean geothermal fluids or other substances injected into a geothermal occurrence by which geothermal energy is transported to the surface.