Plate Tectonics - Definition - Law Dictionary Home Dictionary Definition plate-tectonics

Definition :

A geological theory which holds that the crust of the earth the lithosphere is divided into a small number of large separate plates which float and move slowly around on the more plastic asthenosphere breaking apart and moving away from each other at points where magma upwells from below and driven by such upwellings and other currents on the athenosphere sliding past each other colliding with each other and in some cases being submerged subducted one below the other This theory is now widely accepted and explains many geological phenomena such as the clustered locations of earthquakes mountain building volcanism and the similarities observed between the geology of continents such as South America and Africa which are now far apart but according to the theory were once joined together The motions of such tectonic plates are very slow typically only several centimeters per year but over tens and hundreds of millions of years cause very large changes in the relative positions of the continents The consequence of such movement of plates is called continental drift