The mantle is made of a very thick and dense material, this causes the plates to "float" on it. Geologists strongly believe that the mantle "flows" because of convection currents. When the convection currents provide flow in the mantle they move the earth's crust. The crust gets a boost and it works like a conveyor belt. How does this occur?. It's caused by the very hot material in the deepest part of the mantle, there is a cycle that repeats,over and over - (rising), then cooling, (sinking again) and then heating, (rising.)