plate margin
plate margin (plate boundary) The boundary of one of the plates that form the upper layer (the lithosphere) and together cover the surface of the Earth. Plate margins are characterized by a combination of tectonic and topographic features: oceanic ridges, Benioff zones, young fold mountains, and transform faults. Plate margins are of three main types: (a) constructive margins where newly created lithosphere is being added to plates which are moving apart at oceanic ridges; (b) convergent margins which can be either destructive margins, where one plate is carried down into the mantle, beneath the bordering plate, at a subduction zone, or a collision zone, where two island arcs or continents, or an arc and a continent, are colliding; or (c) conservative margins, where two plates are moving in opposite directions to each other along a transform fault. All three margins are seismically active, with volcanic activity at constructive and destructive margins. Some plate margins exhibit features of more than one of the three main types and are known as combined plate margins. See PLATE TECTONICS; and SEA-FLOOR SPREADING.
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Benioff Zone , Benioff zones are dipping, roughly planar zones of increased earthquake activity produced by the interaction of a downgoing oceanic crustal plate wit… Plate Tectonics , plate tectonics, theory that unifies many of the features and characteristics of continental drift and seafloor spreading into a coherent model and h… Subduction Zone , Subduction zones occur at collision boundaries where at least one of the colliding lithospheric plates contains oceanic crust . In accord with plate… Ocean , Oceans are large bodies of salt water that surround Earth's continents and occupy the basins between them. The four major oceans of the world are the… Project Mohole , Hess, Harry Hammond
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Hess was the son of Elizabeth Engel Hess and of Julian S. Hess, a member of the New… Seafloor Spreading , seafloor spreading, theory of lithospheric evolution that holds that the ocean floors are spreading outward from vast underwater ridges. First propos…
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plate margin