plate tectonics summary

Learn about the theory of plate tectonics

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Below is the article summary. For the full article, see plate tectonics.

Earth's tectonic plates
Map showing Earth's major tectonic plates with arrows depicting the directions of plate movement.

plate tectonics, Theory that the Earth’s lithosphere (the crust and upper portion of the mantle) is divided into about 12 large plates and several small ones that float on and travel independently over the asthenosphere. The theory revolutionized the geological sciences in the 1960s by combining the earlier idea of continental drift and the new concept of seafloor spreading into a coherent whole. Each plate consists of rigid rock created by upwelling magma at oceanic ridges, where plates diverge. Where two plates converge, a subduction zone forms, in which one plate is forced under another and into the Earth’s mantle. The majority of the earthquakes and volcanoes on the Earth’s surface occur along the margins of tectonic plates. The interior of a plate moves as a rigid body, with only minor flexing, few earthquakes, and relatively little volcanic activity.

Pangea Summary

Pangea, in early geologic time, a supercontinent that incorporated almost all the landmasses on Earth. Pangea was surrounded by a global ocean called Panthalassa, and it was fully assembled by the Early Permian Epoch (some 299 million to about 273 million years ago). The supercontinent began to

continental drift Summary

Continental drift, large-scale horizontal movements of continents relative to one another and to the ocean basins during one or more episodes of geologic time. This concept was an important precursor to the development of the theory of plate tectonics, which incorporates it. The idea of a

earthquake Summary

Earthquake, any sudden shaking of the ground caused by the passage of seismic waves through Earth’s rocks. Seismic waves are produced when some form of energy stored in Earth’s crust is suddenly released, usually when masses of rock straining against one another suddenly fracture and “slip.”