Subduction zones

These are when two oceanic plates hit each other, the younger of the two because it is less dense, will move over the edge of the other plate. The Oceanic Plates become more dense when they move away from the Mid-ocean Ridge. The older plate, turns and plunges at a high angle through the athenosphere, and going down into the ground, it forms a trench which sometimes can be as wide as 70 miles wide, more than a thousand miles long and several miles deep.