The creation of oceanic crust and its collision with continental crust cause the continents to move across the Earth's surface over geologic time. Mountain building is the result of plate collisions. For example, the Himalayas were created when the Indian plate crashed into the Eurasian plate. In the collision oceanic sedimentary deposits were pushed vertically to great altitudes. This explains why you can find marine fossils in mountain environments.
Earthquakes are also a result of plate tectonics.
They occur at faults, tectonic plate boundaries, and at the mid-oceanic ridge. Most earthquakes result after the sudden movement of one mass rock relative to another mass. The rock resisted movement in the past because of friction. However, pressure and stress builds up until the friction is overcome. The size of an earthquake is relative to potential energy build up before the friction is overcome.