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3 definitions found
 for plate tectonics
From The Collaborative International Dictionary of English v.0.48 :

  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 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.
     [PJC]

From The Collaborative International Dictionary of English v.0.48 :

  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 Webster]
  
     2. (Geol. & Phys. Geog.) the branch of geology concerned with
        the rock structures and external forms resulting from the
        deformation of the earth's crust; also, similar studies of
        other planets. Also called structural geology.
        [PJC]
  
     plate tectonics a geological theory which considers the
        earth's crust as divided into a number of large relatively
        rigid plates, which move relatively independently on the
        more plastic asthenosphere under the influence of magmatic
        upwellings, so as to drift apart, slide past, or collide
        with each other, causing the formation, breakup, or
        merging of continents, and causing volcanism, the building
        of mountain ranges, and the subduction of one plate
        beneath another. In recent decades a large body of data
        have accumulated to support the theory and provide some
        details of the mechanisms at work. One set of supporting
        observations consists of data showing that the continents
        have slowly moved relative to each other over long periods
        of time, a phenomenon called continental drift. Africa
        and South America, for example, have apparently moved
        apart from a connected configuration at about 2 to 3 cm
        per year over tens of millions of years.
        [PJC]

From WordNet (r) 3.0 (2006) :

  plate tectonics
      n 1: the branch of geology studying the folding and faulting of
           the earth's crust [syn: tectonics, plate tectonics,
           plate tectonic theory]

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