The oceanic crust is made up of rocks much younger than the Earth itself : oceanic crust in the ocean basins is everywhere less than 200 million years old . The new oceanic crust is quite hot relative to old oceanic crust , so the new oceanic basin is shallower than older oceanic basins . If the diameter of the earth remains relatively constant despite the production of new crust , a mechanism must exist by which crust is also destroyed .