The answer is subduction. In locations around the world, ocean crust subducts, or slides under, other pieces of Earth's crust. The boundary where the two plates meet is called a convergent boundary.

Plates at subduction zones typically move just a few centimeters per year. But when accumulated stress at these convergent plate boundaries releases suddenly, the plates can slip several meters ...

For more on divergent boundary, go to The Sea Floor Spread. Also known as subduction boundary, a convergent boundary occurs where one plate slides under another as the two are pushed together.