The theory of plate tectonics describes the movement of the plates of the lithosphere relative to each other. This movement creates forces that push and pull on the crust. Crustal rock can absorb and store energy, but only so much. There is a point at which the stress is more than the rock can hold and the rock breaks. When the rock breaks, the stored energy is released and this energy travels through the Earth. This sudden release of energy created when rocks break is called an earthquake. Read More...