plate tectonics

/pleɪt tɛkˈtɒnɪks/ (say playt tek'toniks)

a theory concerning the movements of the earth's lithosphere that explains how tectonic plates ride on the moving asthenosphere; supporting the theory of continental drift and sea-floor spreading.
The key principle of plate tectonics is that the rigid crustal plates (tectonic plates) that make up the outer layers of the earth are in constant motion driven by convection currents within the asthenosphere or mantle. The plate boundaries, where they collide, move apart or grind against each other, are associated with earthquakes and volcanic activity, such as the Pacific Ring of Fire, and the formation of topographical features such as mountain ranges, rift valleys and oceanic ridges and trenches. The Himalayas, for example, are being pushed up as the Indo-Australian Plate, which is moving north at the rate of five centimetres a year, collides with the Asian Plate. The Australian continent lies in the centre of the Indo-Australian Plate, so earthquake and volcanic activity is low; the Darling Fault, east of Perth, is the result of an old collision. The East African Rift is opening up as the African Plate moves away from the Eurasian Plate. Plate tectonics explains the similarity in rock types, fossils, flora and fauna in different continents, such as Australia and Antarctica, by suggesting that they were joined at one time. See also tectonic plate.

Australian English dictionary. 2014.

Look at other dictionaries:

  • plate tectonics — plate tectonic, adj. Geol. a theory of global tectonics in which the lithosphere is divided into a number of crustal plates, each of which moves on the plastic asthenosphere more or less independently to collide with, slide under, or move past… …   Universalium

  • plate tectonics — plate tectonics, n. (Geol.) 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 …   The Collaborative International Dictionary of English

  • plate tectonics — Tectonics Tec*ton ics, n. 1. The science, or the art, by which implements, vessels, dwellings, or other edifices, are constructed, both agreeably to the end for which they are designed, and in conformity with artistic sentiments and ideas. [1913… …   The Collaborative International Dictionary of English

  • plate tectonics — n. Geol. the theory that the earth s surface consists of plates, or large crustal slabs, whose constant motion explains continental drift, mountain building, etc …   English World dictionary

  • Plate tectonics — The tectonic plates of the world were mapped in the second half of the 20th century …   Wikipedia

  • plate tectonics — noun the branch of geology studying the folding and faulting of the earth s crust • Syn: ↑tectonics, ↑plate tectonic theory • Members of this Topic: ↑Pangaea, ↑Pangea • Hypernyms: ↑morphology, ↑ …   Useful english dictionary

  • plate tectonics — N UNCOUNT Plate tectonics is the way that large pieces of the earth s surface move slowly around. [TECHNICAL] …   English dictionary

  • plate tectonics — plate′ tecton′ics n. gel a geologic theory that describes the earth s crust as divided into a number of rigid plates, movement of which accounts for such phenomena as continental drift and the distribution of earthquakes • Etymology: 1965–70… …   From formal English to slang

  • plate tectonics — plate tec tonics n [U] technical the study of the forming and movement of the large sheets of rock that form the surface of the Earth …   Dictionary of contemporary English

  • plate tectonics — plate tec tonics noun uncount SCIENCE the study of the large layers of rock under the surface of the Earth, and how they were formed and move …   Usage of the words and phrases in modern English

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