Plate Tectonics
Plate tectonics is a theory that really revolutionized the science of geology by linking the internal behavior of the earth to its surface features. It is the theory that the uppermost part of the Earth is made up of 12 rigid lithospheric plates that slowly move laterally over the underlying mantle. The movement of these plates is driven by the convective flow of material in the asthenosphere. This convection starts in the liquid outer core and generally stops at the mantle boundary where heat is then transferred by conduction. However, sometimes these convective currents hit the mantle and continue rising to the base of the crust as vertical currents, called plumes. As these upwelling plumes of hot mantle material impact the base of the lithosphere, they cause lateral spreading, cracking, and rifting. The lithospheric plates continue to split apart and move until they reach a zone of downward flow back into the asthenosphere. This is referred to as a subduction zone.