The large sections of the lithosphere are called tectonic plates. These plates are made up of the crust and upper mantle of the Earth, and they sit on top of the asthenosphere.
The tectonic plates are an important part of understanding the evolution of the appearance of the Earth through the years. In general, the plates measure about 100 to 200 kilometers thick. Underneath these tectonic plates, the hot asthenosphere moves and causes the movement of the plates above.
The movement of these plates causes the land masses to slowly move. Earth looks very different in modern times than millions of years ago. Continents collide and move apart as a result of the plates. The movement of two plates against one another causes earthquakes and forms mountains.