Mountains big and small have been the result of plate teconics.

The formation of the Himalayas was created when the Indian subplate burrowed under the European continent and formed the Appalachian Mountains.

When the North American and African plates collided, a large separation of earth materialized and the Atlantic Ocean opened up.

The volcanic and seismic activity of the West Coast of the US occurs as a result of grinding of the North American and Pacific plates.

The above are just a few examples of the effects of plate tectonics. The geological history of Earth is littered with such phenomena that have made the Earth what it is today.