100kpa is correct If that is not wht you were asking i'd gladly fix it :)
At an oceanic/oceanic plate boundary 2 oceanic plates will collide against each other. The older oceanic plate will sub-duct under the newer one. It will sub-duct into magma, and will melt into it. The plate and magma will create a reaction, and will build up pressure. With enough pressure, magma will erupt creating a volcano.
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Abe chutiye, Question sahi se likh laude phle