Radioisotope dating has helped geologists prove that if a new crust is continuesly formed at oceanic ridges and is pulled apart sideways, rocks will get progressively older the further apart they are from the ridge.
The ocean basins formed at these ridges are relitively young compared to continental crust, being only 200 million years old. When the ages of the sea floor rocks are mapped, the pattern of sea floor spreading becomes aparent, with the newest oceanic crust being at the oceanic ridge while the oldest is the furthest from it.
The pattern of sedimentation on the sea floor near these ridges supports this direct dating. In comparison to the thickness of the sedimentation layers furthest away from the ridge, little or no sediment covers the rocks at the ridge, proving that ocean rocks increase with age the further they move away from the oceanic ridge.
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| This diagram shows us an oceanic ridge with the differently shaded rock layers signifiying the theory that the further apart the top layer drifs the older it gets, with the least oldest being in the middle. |
This evidence convinces us to believe the continental drift theory, because we can see that new rocks are continuesly being formed at the oceanic ridge and the oldest rocks are going to consistantly separate, proving that they were once joined and are still in the process of separating.
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