The Theory of Plate Tectonics

The lithosphere is made from the crust and the uppermost part of the mantle

The lithosphere is rigid, brittle rock

These plates float on the asthenosphere

The super continent that Alfred Wegener described in his theory of Continental Drift

Convection currents in the asthenosphere drive the movement of lithospheric plates

Hot magma in the asthenosphere begins to rise, similar to the way hot air rises.

As it rises to the top of the asthenosphere, it cools and becomes more dense.

This cooler, dense magma then sinks again. As it sinks, it gets warmer, until the process begins again

This movement of magma is what drives the plates to move.