The plates of the Earth’s surface move because of the intense heat in the Earth’s core, which causes it to move the molten rock in the mantle. It moves in a pattern called a convection cell, which is formed when a material emerges, cooled and eventually, it sinks. As the cold material sinks, heated and re-emerge.
At some point, scientists thought that the Earth’s plates moved only on the giant convection cells, but now believe that the plates have proper motion, rather than just travel. Just like convection cells, plates have warmer, thinner parts, which are more likely to emerge, and cold, dense parts, more likely to sink.
The new plate parts emerge because they are hot, and because the plate is thin. As the hot magma rises to the surface of the spreading ridges and forms new crust, the new crust pushes the rest of the board out of the way.
It is likely that the old plate layers to sink towards the mantle of subduction zones because they are cooler, and are thicker and denser than the mantle material is below them. This is called, push plates.
This image shows a cross section showing the Earth’s mantleconvection cells. The thrust of ridges occurs towards the center,where plates are separating. The thrust plate occurs in subduction zones, where a plate is pushed down into the mantle.