When an oceanic plate and a continental plate collide Convergent boundaries are formed.
When a plate of solid oceanic lithosphere leading in one direction strikes with a plate leading in the reverse direction, one of the plates subducts below the other. Where this happens an oceanic depression forms on the sea and the drowning plate converts into the subduction zone. Moreover, Island arcs and oceanic channels occur if both of the plates are composed of oceanic crust.