The upper layer of the Earth is called the lithosphere and it is not broken into more than a dozen continents that move very slowly in various directions. The lithosphere is divided into several tectonic plates, which are large pieces of the Earth's crust and upper mantle that move relative to each other. There are seven major tectonic plates and a number of smaller ones. These plates move very slowly, at rates of a few centimeters per year, and they can move in different directions. The movement of the tectonic plates is driven by convection currents in the Earth's mantle.