'Heat, although not a "substance" in the physical sense, behaves in many ways analogous to water.'
Heat from the earth, or geothermal heat, arises from the heat dissipated from the centre of the earth and, at shallow depth, from heating by the sun. High-enthalpy (deep) geothermal heat is found within some granitic rocks due to slightly raised levels of the radiogenic isotopes of potassium, uranium and thorium.
Download the science briefing paper Who owns geothermal heat? from the British Geological Survey (BGS)
