Ocean-Ocean Collisions

When 2 oceanicplates collide one oceanic plate is eventually subducted under the other.Where one bowl slides under the various other is referred to as the "subductionzone". As the subducting bowl descends right into the mantle whereby it is beinggradually boil a benioff ar is formed. This benioff zone is a zone ofshallow,intermediate and also deep focused earthquakes. Some deep focused earthquakesthat happen at ocean ocean- collision boundaries can be together deep together 670 kilometres.As the subducted bowl descends into the mantle it is slowly heated allowingthe formation of magma. The magma that creates is andesitic in compositionand begins to type when the subducted bowl reaches a depth that 100 kilometres.This andesitic magma is created from the partial melting of the asthenospherejust over the subduction zone. This partial melting of the subducting plateis due to the loss of water together it descends into the mantle. The andesiticmagma is now less dense than the surrounding product so it rises throughthe crust and also erupts to kind an arc that volcanoes dubbed an island arc. Thedistance between the trench and also the island arc depends considerably upon wherethe subducting bowl reaches the 100 kilometre depth. If the subduction angleis steep climate the distance in between the arc and also the trench will certainly be short.Ifthe suduction angle is shallow the distance is longer. The key featuresare suggested in the diagram below. The swell is seen by a bulge in the in the downgoing plate wherein it is subducted into the mantle.where the platesubducts right into the mantle is well-known as the trench.the forearc ridge containshighly deformed sedimentary and metemorphic rock. The backarc region is locatedbehind the arc and also can it is in compressed or extended.


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Fig.2.1. Ocean-ocean collision zone

Ocean-Continent Collisions

When one oceanicand a continental plate collide, eventually the oceanic bowl is subductedunder the continental plate due to the high density of the oceanic plate.Once again a benioff zone forms where there room shallow intermediate anddeep emphasis earthquakes. Together the oceanic bowl is subducted sediment is scrapedoff to form an acretionary wedge at the suggest of collision in between the twoplates. When the oceanic bowl is subducted as result of partial melting of theasthenosphere magma v an andesitic composition is formed. The magma formedis less dense than the surrounding product so that rises come the surface toform a magmatic arc on the leaf of the continent i m sorry the oceanic plateis subducted under. With time the continent margin, as result of compressionforms into a folded hill belt. Together time go on the hot magma increasing upwardfrom the subduction zone reasons further compression that the mountain belt.Deep hill roots form and are slowly metamorphosed and intruded v granitic plutons.Explosive volcanic task is commonly associated withthis form of collision boundary. This is presented in the diagram below.The majorcomponants of one oceanic - continent collision zone and a accretionarywedge are additionally shown in the diagrams below.
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Fig.2.2 Ocean-continent collision region
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Fig.2.3. Deformation at an ocean-continent collisionzone

Continent-Continent Collision

When 2 continentalplates collide neither plate have the right to be subducted as result of their high bouyancy.With this kind of collision there space no functions such as a subduction zone,trench or acretionary wedge. The collision of 2 continental key occurswhen a sea i do not care narrower until both plates collide. ~ collision theoceanic lithosphere breaks off and sinks right into the mantle. The subductionzone ultimately becomes inactive The two continents become welded togetheras they space compressed together over time. The late is thickened by theunderthrusting of one continent under the other. This regions have actually bothshallow emphasis earthquakes and deep focus earthquakes as the oceanic lithosphereis subducted under the mounatin range. Thrust faults and also highly metamorphisedgranites are typical charcteristics of these collision zones. The many wellknown example of this collision zone is the Himalayas whereby India has collidedwith Asia.

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Fig.2.4. Continent-continent collision zone
Mechanisms the Plate motion
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