When two Oceanic plates meet, one plate sinks below the other. The oceanic plate that sinks is usually older, colder. The denser plate will bend and sink into the mantle. New magma will then form as the magma rises from the volcano. As with the convergence of oceanic-continental plates, trenches are formed at the subduction zone. Challenge deep, the deepest part of the oceans, is part of the Mariana Trench in the subduction zone between the Pacific and Philippine Plates. Challenger deep is very deep that not even mount Everest could fit it.