Earthquakes seemed to outline a special feature of earth's crust. Earthquakes let scientists know where the crust was moving. This led to the discovery that the Earths crust was broken up into regions, or plates. Earthquakes happen most often along these plate boundaries. This was evidence that continents can move. The movements of the plates are called plate tectonics. The Earths crust is divided into plates. There are about a dozen large plates and several small ones. Each plate is named for the continent or ocean basin it contains. Scientists know he plates are in motion. They now know the direction and speed of this motion . Plates dont move very fast. They move only a few centimeters a year. This is about the same rate fingernails grow. So you might wonder, what could cause this motion? What supplies the energy to cause this change? 
How many plates is the earth's crust divided into?
Uncountable