One of the principal difficulties in establishing the theory of continental drift (the idea that tectonic plates drift around on Earth's surface) was identifying a source of energy capable of powering such movements. What do we now believe to be the source of this energy?

The energy that drives this movement is heat within the earth, this heat comes from two main sources which are;

1) residual heat left over from the formation of our planet billions of years ago.

2) The radioactive decay of naturally occurring chemical elements (notably uranium, thorium, and potassium) in the earth releases energy in the form of heat. These two sources of heat warm Earth's mantle and cause it to rise and sink, this rising and sinking creates a convectional movement of earth mantle.