The earth has many layers. 

The outer layer (the lands and water) is called the crust.
The crust is broken up into huge pieces of rock called plates. 

These plates are always moving.
Earth quakes happen when one plate slips beneath another or when they grind past each other.
Scientists think the movement of earth's plates may have causes the continents to break up and move over millions of years!

This process is called plate tectonics, and the large mass of earth before we have continents is called Pangea.
Mountains are created when earth's crust plates move and bump into each other.