Shallowing

The main 200-feet basin is about 8 miles long; it includes three areas of over 300 feet, which, however, are only separated by very slight shallowings.

And this shallowing, reinforced by the creation of mid-ocean ridges as the supercontinents split up, forced the world’s oceans to overflow, changing the outlines of the continents and all but sinking some of the European islands.