plates to move
Convection within the Earths mantle causes the plates to move. Mantle material is heated above the core. The hot mantle rises up towards the surface Figure below . As the mantle rises it cools. At the surface the material moves horizontally away from a mid-ocean ridge crest. The material continues to cool. It sinks back down into the mantle at a deep sea trench. The material sinks back down to the core. It moves horizontally again, completing a convection cell.