<P> Geothermal energy is heat energy generated and stored in the Earth . Thermal energy is the energy that determines the temperature of matter . The geothermal energy of the Earth 's crust originates from the original formation of the planet and from radioactive decay of materials ( in currently uncertain but possibly roughly equal proportions ) . The geothermal gradient , which is the difference in temperature between the core of the planet and its surface , drives a continuous conduction of thermal energy in the form of heat from the core to the surface . The adjective geothermal originates from the Greek roots γη ( ge ) , meaning earth , and θερμος ( thermos ) , meaning hot . </P>
where does the heat energy for geothermal energy resources come from
from the original formation of the planet from radioactive decay of materials