Ocean-Ocean Collisions

When two oceanicplates collide one oceanic bowl is eventually subducted under the other.Where one bowl slides under the other is referred to as the "subductionzone". Together the subducting key descends into the mantle wherein it is beinggradually heated a benioff zone is formed. This benioff ar is a zone ofshallow,intermediate and deep focused earthquakes. Some deep concentrated earthquakesthat take place at s ocean- collision borders can be together deep as 670 kilometres.As the subducted key descends into the mantle the is slowly heated allowingthe development of magma. The magma that forms is andesitic in compositionand starts to form when the subducted plate reaches a depth of 100 kilometres.This andesitic magma is developed from the partial melt of the asthenospherejust above the subduction zone. This partial melting of the subducting plateis as result of the ns of water as it descends right into the mantle. The andesiticmagma is currently less thick than the surrounding material so the rises throughthe crust and erupts to type an arc that volcanoes dubbed an island arc. Thedistance in between the trench and the island arc depends considerably upon wherethe subducting plate reaches the 100 kilometre depth. If the subduction angleis steep then the distance in between the arc and the trench will be short.Ifthe suduction angle is shallow the distance is longer. The main featuresare indicated in the diagram below. The swollen is checked out by a bulge in the in the downgoing plate where it is subducted into the mantle.where the platesubducts right into the mantle is known as the trench.the forearc ridge containshighly deformed sedimentary and also metemorphic rock. The backarc region is locatedbehind the arc and also can be compressed or extended.


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Fig.2.1. Ocean-ocean collision region

Ocean-Continent Collisions

When one oceanicand a continental plate collide, ultimately the oceanic key is subductedunder the continent plate due to the high thickness of the oceanic plate.Once again a benioff zone forms where there are shallow intermediary anddeep focus earthquakes. As the oceanic key is subducted sediment is scrapedoff to type an acretionary wedge in ~ the allude of collision between the twoplates. Once the oceanic plate is subducted as result of partial melting of theasthenosphere magma with an andesitic composition is formed. The magma formedis less dense than the surrounding material so the rises come the surface toform a magmatic arc on the leaf of the continent i m sorry the oceanic plateis subducted under. Over time the continental margin, because of compressionforms into a folded mountain belt. Together time goes on the hot magma increasing upwardfrom the subduction zone reasons further compression of the hill belt.Deep mountain roots kind and are slowly metamorphosed and intruded through granitic plutons.Explosive volcanic task is commonly connected withthis form of collision boundary. This is displayed in the diagram below.The majorcomponants of one oceanic - continent collision zone and also a accretionarywedge are also shown in the diagrams below.
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Fig.2.2 Ocean-continent collision zone
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Fig.2.3. Deformation at an ocean-continent collisionzone

Continent-Continent Collision

When 2 continentalplates collide neither plate can be subducted as result of their high bouyancy.With this kind of collision there are no attributes such together a subduction zone,trench or acretionary wedge. The collision of two continental key occurswhen a sea i do not care narrower till both key collide. ~ collision theoceanic lithosphere breaks off and also sinks right into the mantle. The subductionzone eventually becomes inactive The two continents end up being welded togetheras they room compressed with each other over time. The late is thickened through theunderthrusting the one continent under the other. These regions have actually bothshallow emphasis earthquakes and deep emphasis earthquakes as the oceanic lithosphereis subducted under the mounatin range. Thrust faults and highly metamorphisedgranites are common charcteristics of this collision zones. The most wellknown example of this collision ar is the Himalayas wherein India has collidedwith Asia.

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Fig.2.4. Continent-continent collision ar
Mechanisms the Plate movement
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