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===Convergent Plate Boundaries===

===Convergent Plate Boundaries===

Convergent plate boundaries are the collisions between tectonic plates. The collisions between tectonic plates can be distinguished into ocean-ocean convergent, ocean-continent convergent, or continent-continent convergent. The character of the boundary depends partly on the type of plates that converge. In ocean-ocean convergent, a plate can move toward another plate, where one plate subducts under the other. While, in ocean-continent convergent, the dense oceanic plate subducts under the continental plate. In continent-continent convergent, the two approaching plate collide and crumple but neither is subducted.

Convergent plate boundaries are the collisions between tectonic plates. The collisions between tectonic plates can be distinguished into ocean-ocean convergent, ocean-continent convergent, or continent-continent convergent. The character of the boundary depends partly on the type of plates that converge. In ocean-ocean convergent, a plate can move toward another plate, where one plate subducts under the other. While, in ocean-continent convergent, the dense oceanic plate subducts under the continental plate. In continent-continent convergent, the two approaching plate collide and crumple but neither is subducted.<ref>Carlson, Plummer, Hammersley. ''PHYSICAL GEOLOGY: Earth Revealed''. 9th edition. New York: The McGraw-Hill Companies, Inc, 2011. ISBN 978-0-07-122184-9</ref>

[[File:Ocean-ocean.jpg|framed|center|Ocean-Ocean Convergent <ref> http://oceansjsu.com/images/exp5_oceanocean_conv.gif </ref>]]

[[File:Ocean-ocean.jpg|framed|center|Ocean-Ocean Convergent <ref> http://oceansjsu.com/images/exp5_oceanocean_conv.gif </ref>]]

[[File:Continental-ocean.jpg|framed|center |Ocean-Continent Convergent <ref> http://geology.com/usgs/gold-prospecting/convergent-boundary-and-magma.jpg </ref>]]

[[File:Continental-ocean.jpg|framed|center |Ocean-Continent Convergent <ref> http://geology.com/usgs/gold-prospecting/convergent-boundary-and-magma.jpg </ref>]]

[[File:Ridge_push-slab_push.jpg|framed|right|Ridge Push and Slab Pull Mechanism <ref> http://www.tulane.edu/~sanelson/images/mantleconvect.gif

[[File:Ridge_push-slab_push.jpg|framed|right|Ridge Push and Slab Pull Mechanism <ref> http://www.tulane.edu/~sanelson/images/mantleconvect.gif

  </ref>]]

  </ref>]]

Ridge push or sliding plate force is a proposed mechanism for plate motion in plate tectonics. When a plate moves away from a divergent boundary, it cools and thickens. Cooling sea floor subsides as it moves, and this subsidence forms the broad side slopes of the mid-ocean ridge. An even more important slope form on the base of the lithosphere mantle. The mantle thickens as cooling converts asthenospheric mantle to lithospheric mantle. Therefore, the boundary between them is a slope down which the lithosphere slides. The oceanic plate is thought to slide down this slope at the base of lithosphere, which may have a relief of 80 to 1000 kilometres.

Ridge push or sliding plate force is a proposed mechanism for plate motion in plate tectonics. When a plate moves away from a divergent boundary, it cools and thickens. Cooling sea floor subsides as it moves, and this subsidence forms the broad side slopes of the mid-ocean ridge. An even more important slope form on the base of the lithosphere mantle. The mantle thickens as cooling converts asthenospheric mantle to lithospheric mantle. Therefore, the boundary between them is a slope down which the lithosphere slides. The oceanic plate is thought to slide down this slope at the base of lithosphere, which may have a relief of 80 to 1000 kilometres.<ref>Carlson, Plummer, Hammersley. ''PHYSICAL GEOLOGY: Earth Revealed''. 9th edition. New York: The McGraw-Hill Companies, Inc, 2011. ISBN 978-0-07-122184-9</ref>

===Slab Pull===

===Slab Pull===

The other proposal is called slab pull. Cold lithosphere sinking at a steep angle through hot mantle should pull the surface part of the plate away from the ridge crest and then down into mantle as it cools. A subduction plate sinks because it is denser than the surrounding mantle. This density contrast is partly due to the fact that sinking lithosphere is cold. The subduction plate may also increase its density while it sinks, as low-density materials such as water are lost and as plate minerals collapse into denser form during subduction. Slab pull is thought to be at least twice as important as ridge push in moving an oceanic plate away from aridge crest. Slab pull causes rapid plate movement.  

The other proposal is called slab pull. Cold lithosphere sinking at a steep angle through hot mantle should pull the surface part of the plate away from the ridge crest and then down into mantle as it cools. A subduction plate sinks because it is denser than the surrounding mantle. This density contrast is partly due to the fact that sinking lithosphere is cold. The subduction plate may also increase its density while it sinks, as low-density materials such as water are lost and as plate minerals collapse into denser form during subduction. Slab pull is thought to be at least twice as important as ridge push in moving an oceanic plate away from aridge crest. Slab pull causes rapid plate motion.<ref>Carlson, Plummer, Hammersley. ''PHYSICAL GEOLOGY: Earth Revealed''. 9th edition. New York: The McGraw-Hill Companies, Inc, 2011. ISBN 978-0-07-122184-9</ref>

==Continental Drift==

==Continental Drift==

=References=

=References=

<references />

<references />

* Carlson, Plummer, Hammersley. ''PHYSICAL GEOLOGY: Earth Revealed''. 9th edition. New York: The McGraw-Hill Companies, Inc, 2011. ISBN 978-0-07-122184-9

* <ref>Carlson, Plummer, Hammersley. ''PHYSICAL GEOLOGY: Earth Revealed''. 9th edition. New York: The McGraw-Hill Companies, Inc, 2011. ISBN 978-0-07-122184-9</ref>

* Christian Vérard, Cyril Hochard, Peter O. Baumgartner, Gérard M. Stampfli. 2015. ''Geodynamic evolution of the Earth over the Phanerozoic: Plate tectonic activity and palaeoclimatic indicators''. Journal of Palaeogeography, 4(2): 167-188.

* Christian Vérard, Cyril Hochard, Peter O. Baumgartner, Gérard M. Stampfli. 2015. ''Geodynamic evolution of the Earth over the Phanerozoic: Plate tectonic activity and palaeoclimatic indicators''. Journal of Palaeogeography, 4(2): 167-188.

* http://csmres.jmu.edu/geollab/vageol/vahist/plates.html

* http://csmres.jmu.edu/geollab/vageol/vahist/plates.html