geothermal energy is formed by magma heating earth 's crust
global_warming is heating. volcanic_rock is igneous_rock. heat is form_of_energy. geothermal_energy is energy. earths_core is magma. thermals is rising_currents_of_warm_air. magma is rock. magma is ver_hot. basalt is igneous_rock. geothermal_energy is heat.