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Plate tectonics and basin formation (view source)
Revision as of 15:40, 30 June 2015
, 15:40, 30 June 2015no edit summary
===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.
[[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:Cont-cont.jpg|framed|center|Continent-Continent Divergent <ref> http://geomaps.wr.usgs.gov/parks/pltec/contvscont289x153.gif </ref>]]
==The Cause of Plate Motion==
===Mantle Convection===
The widely accepted opinion regarding the cause of the plates move at this time is because of the convection currents in the mantle. The heat from the core of the Earth is transferred to the surface of the Earth through the mantle. The heat from the core warms up the liquid rock on mantle that closest to the core, causing the liquid rock to expand and rise toward the crust. The cooler liquid rock near the surface sinks back down toward the core. In doing so, a current of liquid rock is set up flowing toward the surface and back down again. This mantle convection is believed the causes the plates movement.
[[File:Mantle_convection_cell.jpg|framed|center|Mantle Convection <ref> http://research.bpcrc.osu.edu/education/rr/plate_tectonics/mantle_convection_cell.gif
</ref>]]
===Ridge Push===
[[File:Ridge_push-slab_push.jpg|framed|right|Ridge Push and Slab Pull Mechanism <ref> http://www.tulane.edu/~sanelson/images/mantleconvect.gif
</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.
===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.
==Continental Drift==
[[File:Continental_drift1.jpg|framed|center|Continental Drift <ref> http://media-1.web.britannica.com/eb-media/99/101699-004-066A8D00.jpg </ref>]]
The revolution in the science of earth has been started since the early 19th century, when the emergence of a radical thought at that time to propose a hypothesis about the continents that move on the surface of the earth. Actually, the theory of plate tectonics already emerged when the idea of the Flotation hypothesis Continent (Continental Drift) was introduced first time by Alfred Wegener (1915) in his book "The Origins of Oceans and Continents". An effect of this floatation continent hypothesis is a hypothesis which assumes that the continents that exist today united formerly known as the super-continent called Pangaea. This super-continent Pangaea allegedly formed 200 million years ago which was then fragmented into pieces smaller then migrate or drifted into position as it is today.
Proof of the existence of the super-continent Pangaea 200 million years ago supported by the facts as follows:
===The similarity of shorelines===
The lack of compatibility coastline in the eastern part of the South American continent with a coastline of the western part of the African continent. Both this coastline when matched to one another will coincide. Wegener suspected that both continents were originally one. Based on the lack of compatibility shape of the coastline was then Wegener tried to match all the continents on earth.
===The discovery of fossils from animals and plants are widespread and separated on several continents===
* Cynognathus fossil, a reptile that lived about 240 million years ago and was found in the South American continent and the African continent.
* Mesosaurus fossil, a reptile that lived in freshwater lakes and rivers that lived about 260 million years ago, was found in the South American continent and the African continent.
* Lystrosaurus fossil, a reptile that lived on land around 240 million years ago, was found in the continent of Africa, India and Antarctica.
* Clossopteris fossils, a plant that lived 260 million years ago, was found in the continent of Africa, South America, India, Australia, and Antarctica.
===The evidence of ancient climate===
Earth scientist has also been studying the ancient climate, where in 250 million years ago was known that the southern hemisphere at the time it happened a cold climate, where the southern hemisphere was covered by a very thick layer of ice, such as in Antarctica, Australia, South America, Africa, and India. The areas that affected by glaciation in mainland Africa turned constantly to the equatorial region. However, this argument was later rejected, because for a period of glaciation in the southern hemisphere, the northern hemisphere tropical climates was characterized by the development of tropical swamp forests were extremely widespread and was the origin of the coal deposits in America eastern, Europe and Asia.
At this time, experts believe that the new terrestrial land experiencing glaciation came from the mainland, known as the super-continent Pangaea that located deep in the southern part of the current position. The evidence of Wegener to support the hypothesis of continental drift that newly acquired after 50 years of prior public geoscientists believe the truth of the hypothesis of continental drift.
===The similarity of rock type===
The Appalachian mountain path are located in the eastern part of the North American continent with the spread trending northeast and suddenly disappear on the beach Newfoundlands. Mountains that has a same age with the Appalachian mountains are also found in the British Isles and Scandinavia. Both of these mountains would form a continuous mountain paths. By way of uniting or matching the appearance of geological forms that separated by an ocean is needed, but the data are not sufficient to prove the hypothesis of a continental drift. In other words, if a continent has experienced separation from one another, it is absolutely necessary evidence that the geological structure and rock types is suitable or appropriate. Although the evidence of geological appearance is matched between the continents, but it is not enough to prove that the continent has undergone floatation.
=Basin Formation=
One of the geologic events can be explained by the theory of plate tectonics was the formation of basin.
==What's Basin?==
Basin in geology is defined as a low area in the Earth’s crust, of tectonic origin, in which sediments accumulate. Basins range in size from as small as hundreds of meters to large parts of ocean basins.
How basin can be created? On some cases with a small scale, fault movements can create relief of hundreds to thousands of meters laterally, resulting in small but often deep basins. But, the other main reason is because the continent rift. In plate tectonic theory, if one of plates rifting into pieces diverging apart then new basins being born, followed by motion reversal, convergence back together, plate collision, and mountain building.
=Reference=
=Reference=
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