Plates move over the soft asthenosphere.
New oceanic lithosphere is created. But the idea did not take hold because there were not enough corroborating data. Thus, Hess gets credit for synthesizing the concept of sea floor spreading just as much evidence was mounting that would eventually support it. Plates are neither produced or destroyed at these boundaries, but there is a good deal of friction between the sliding plates. Over the next several lectures, we will be interpreting the features of the sea floor.