Why is the Earth still hot?
The heat was generated by the violent accumulation of
planetesimals which created the Earth. Further heat is added by decay of radioactive
elements. The main source is the crystallization of our iron core from
liquid to solid. The heat has trouble getting out because of the
large volume to surface area ratio. Smaller planets cool faster.
Heat is carried out from the interior by “convection”. Hot
rock rises
up to the surface where it radiates its energy and cools, sinking back down.
This
causes the dynamics on our crust.