Tectonic Plate Motions

Earth’s outermost layer is the lithosphere, which includes the crust and the upper mantle. This rigid layer is broken into pieces called tectonic plates. But what causes these plates to move?

The answer lies below these plates in the asthenosphere, a partially molten, flowing layer of rock. This layer allows the tectonic plates to move.

This movement of tectonic plates is caused by convection currents within the Earth's mantle.

The mantle material, heated at the Earth's core, rises toward the surface. As it approaches the surface, the material cools and moves horizontally, spreading outward from areas like mid-ocean ridges.

The material continues to cool as it moves and eventually sinks back into the mantle at deep-sea trenches. This sinking material moves horizontally near the core and then rises again, completing a convection cell.

During this cycle, magma rises to the surface at mid-ocean ridges, creating a new seafloor in a process called seafloor spreading. This pushes the tectonic plates apart and reshapes the Earth's surface.