plate tectonics

Plate Tectonics Plate tectonics is the theory that the lithosphere (the outer part of solid Earth) is divided into a small number of plates that float on and travel independently over the Earth's mantle. Much of the Earth's seismic activity and volcanism, along with mountain-building processes, occurs at the boundaries of these plates. The surface of the Earth is composed of about a dozen large plates and several small ones. Within each plate the rocks …

…in any detail the implications of the plate-tectonic theory for the evolution of continental orogenic belts; most thought had been devoted to the oceans. In 1969 John Dewey of the University of Cambridge outlined an analysis of the Caledonian-Appalachian orogenic belts in terms of a complete plate-tectonic cycle of events, and this provided a model for the interpretation of other pre-Mesozoic (Paleozoic and Precambrian) belts. For a detailed discussion of plate-tectonic theory and its far-reaching effects,