Oceanic-Oceanic Convergence
When an oceanic plate meets up with another oceanic plate, the colder, the older, and denser oceanic plate starts to bend and sink into the mantle part. After that new crust is made, while magma rises up to form volcanoes, it can also make under water volcanoes. Oceanic-oceanic convergence can also create deep-sea trenches like Oceanic-Continental Convergence. However over millions and millions of years all the erupted lava and debris pile up on top of the ocean floor until a submarine volcano comes aboves sea level to make and form an island.
http://www.passmyexams.co.uk/GCSE/physics/images/oceanic_oceanic.gif
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