 As the tectonic plates migrate , the ocean floor is subducted under the leading edges of the plates at convergent boundaries . At the same time , the upwelling of mantle material at divergent boundaries creates mid @-@ ocean ridges . The combination of these processes continually recycles the oceanic crust back into the mantle . Due to this recycling , most of the ocean floor is less than 100 Ma old in age . The oldest oceanic crust is located in the Western Pacific , and has an estimated age of about 200 Ma . By comparison , the oldest dated continental crust is 4030 Ma . 
