OCEAN - OCEAN CONVERGENCE : FORMATION OF ISLAND ARCS
CONCEPT : The Islands Arcs are narrow chains of islands which is originated the active volcanoes along the oceanic- oceanic convergence tectonics boundary.The oceanic - oceanic boundary is formed due to the movement of plates towards each other and more dense oceanic plate is subducted under less dense oceanic crust, forming a trench along the boundary. However, the ocean floor is loaded with sediment into the trench.The subducted plate reaches 100 km and enters viscous asthenosphere,melting subducted plates become less dense and push the magma upward due to buoyant force.the flowing of magma is up warded violently and is created new crust along the boundary. Continuous up welling of magma and creating new crust formed a chain of volcanic islands.
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OCEAN OCEAN CONVERGENCE BOUNDARY
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TECTONISM AND VOLCANISM |
TECTONICAL ACTIVITY AND FORMATION :
Islands Arcs are formed due to convergence boundary.The denser oceanic plate is subducted into the lesser oceanic crust at 45 degree angle and enters asthenosphere which is viscous in nature.After forming a trench, the sediments is loaded on the ocean floor , up welling magma pushes the sediments upward , forming a new crust along the boundary.this process is repeated again and formed a narrow chains of active volcanoes.
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STRUCTURE OF ISLAND ARCS |
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FORMATION OF ISLAND ARCS
SOME NOTABLE EXAMPLE OF ISLAND ARCS
FORMATION OF PHILIPPINE ISLAND ARCS
The Philippine Island Arcs formed due to minor plate i.e. Sunda plate which is part of Eurasian plate( continental plate) and Philippine plate ( oceanic plate) ,forming Philippine plate.
FORMATION OF MARIANA TRENCH
The formation of Mariana Trench,two most oceanic plate i.e. Pacific plate and Philippine collides each other and Philippine plate is subducted beneath the Pacific plate,forming Mariana Trench and challenger deep.
MARIANA TRENCH
FORMATION OF JAPAN ISLAND ARCS
Japan island arc formed due to triple junction .i.e. in the northern part Pacific Plate is subducted under Eurasian Plate,forming Japan Trench.in the southern part Philippine plate subducted underneath the Eurasian Plate, Ryukyu Trench formed.The force exerted by the Philippine plate and Eurasian plate give rise to east china sea.in the central part give rise to Izu Trench due to pacific plate and Philippine plate. Japan sea originated due to enforcement of pacific plate and Philippine plate.
JAPAN ISLAND ARCS
JAPAN SEA
JAPAN TRENCH
FORMATION OF INDONESIAN ARCHIPELAGO
The term of Archipelago means a extensive group of islands. The formation of The Indonesia Archipelago,The two plates i.e Indo - Australian plate subducted below Sunda Plate, Forming a Sunda Trench ( Java Trench is part of Sunda.)
INDONESIAN ARCHIPELAGO
FORMATION OF CARIBBEAN ISLANDS
Caribbean Islands formed due collision of North American plate and Caribbean oceanic plate respectively.the trench which is formed there is Puerto Rico.
CARIBBEAN ISLANDS
There are so many islands formed along the convergence boundary.some are mentioned above.
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