Plate Tectonics
Plate Tectonics is a scientific theory. It describes the large scale motions Earth's lithosphere has encountered. There are currently seven or eight major tectonics plates and several smaller ones. The lithosphere plates ride on the Asthenosphere. Oceanic trench, volcanic activity, mountain-building, and earthquakes occur along these boundaries. The tectonic plates are formed from two types of lithospheres: thicker continental and thin oceanic.