Ocean-Ocean Collisions

When 2 oceanicplates collide one oceanic plate is ultimately subducted under the other.Where one key slides under the other is described as the "subductionzone". As the subducting key descends into the mantle whereby it is beinggradually boil a benioff ar is formed. This benioff ar is a ar ofshallow,intermediate and also deep concentrated earthquakes. Part deep focused earthquakesthat occur at ocean ocean- collision boundaries can be together deep as 670 kilometres.As the subducted plate descends into the mantle that is progressively heated allowingthe development of magma. The magma that creates is andesitic in compositionand starts to kind when the subducted bowl reaches a depth the 100 kilometres.This andesitic magma is developed 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 right into the mantle. The andesiticmagma is now less thick than the surrounding product so it rises throughthe crust and erupts to type an arc the volcanoes dubbed an island arc. Thedistance in between the trench and also the island arc depends considerably upon wherethe subducting key reaches the 100 kilometer depth. If the subduction angleis steep then the distance in between the arc and also the trench will be short.Ifthe suduction edge is shallow the distance is longer. The main featuresare shown in the chart below. The swollen 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 recognized as the trench.the forearc ridge containshighly deformed sedimentary and 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 continent plate collide, ultimately the oceanic plate is subductedunder the continental plate because of the high density of the oceanic plate.Once again a benioff zone forms where there room shallow intermediary anddeep focus earthquakes. Together the oceanic key is subducted sediment is scrapedoff to form an acretionary wedge at the suggest of collision between the twoplates. When the oceanic key is subducted due to partial melt of theasthenosphere magma with an andesitic composition is formed. The magma formedis less dense than the surrounding product so that rises come the surface toform a magmatic arc top top the sheet of the continent i m sorry the oceanic plateis subducted under. With time the continental margin, due to compressionforms into a folded hill belt. Together time walk on the warm magma rising upwardfrom the subduction zone reasons further compression that the mountain belt.Deep mountain roots kind and are slowly metamorphosed and intruded through granitic plutons.Explosive volcanic task is commonly associated withthis type of collision boundary. This is presented in the diagram below.The majorcomponants of an oceanic - continental collision zone and a accretionarywedge are also shown in the diagrams below.
Fig.2.2 Ocean-continent collision region
Fig.2.3. Deformation in ~ an ocean-continent collisionzone

Continent-Continent Collision

When 2 continentalplates collide no plate have the right to be subducted due to their high bouyancy.With this type of collision there room no functions 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 plates collide. After collision theoceanic lithosphere breaks off and also sinks right into the mantle. The subductionzone at some point becomes inactive The 2 continents end up being welded togetheras they space compressed together over time. The crust is thickened through theunderthrusting of one continent under the other. These regions have actually bothshallow emphasis earthquakes and also deep focus earthquakes together the oceanic lithosphereis subducted under the mounatin range. Thrust faults and highly metamorphisedgranites are usual charcteristics of this collision zones. The most wellknown example of this collision region is the Himalayas where India has actually collidedwith Asia.

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