The unflattering average shape of Earth. In the process, some of its gravitational potential energy was converted to heat. Some terms defined Heat flow is the quantity of heat escaping per unit time across each unit area of Earth's solid surface Geothermal gradient is the difference in temperature per unit distance in the Earth. We typically refer to the temperature change per kilometer change in depth. A hot pot transfers its heat energy to your hand by conduction if you place your hand in contact with the pot.
Conduction is an important heat-transfer mechanism in Earth's crust and lithosphere.
Cool particles move to hotter regions, where they gain heat energy from the surrounding hotter particles. Boiling water exemplifies convection, as it rises from the hot base of the pot, cools at the surface, and sinks to be heated again. Convection is an important heat-transfer mechanism below Earth's lithosphere, and is locally important in hydrothermal systems in Earth's crust. The infrared radiation generated by a toaster is able to heat bread to make toast. Radiation is not thought to be an important heat transfer mechanism in Earth's interior, because of the opacity of the materials in Earth's interior.