Plate tectonics

Summary

Plate tectonics is the theory that the outer shell of the Earth, the lithosphere, is broken into a few rigid plates. The plates move over the weaker mantle below. Almost all deformation, earthquakes and volcanism are concentrated at the boundaries between plates. Because the plates are rigid pieces of a spherical shell, the relative motion of two plates is a rotation about an Euler pole. The theory explains the distribution of earthquakes, mountain belts, ocean ridges and trenches, and the drift of continents.