Plate Tectonics is a theory explaining the structure of the earth's crust and many associated phenomena as resulting from the interaction of rigid plates that move slowly over the underlying mantle. Why does the earth's plate tectonics move? Tectonic plates move because, they are floating on top of the liquid mantle. The mantle itself moves due to convection currents. Also hot rock rises and gives off some heat, then falls. This creates vast swirls of moving liquid rock under the crust of the earth, which jostles the plates of crust on top. A theory is that all the continents can fit together like puzzle pieces. The Atlantic coasts of Africa and South America appear to fit together neatly, like the pieces of a puzzle. The same