shallowing

verb

1. (form-of, gerund, participle, present)present participle and gerund of shallow

noun

1. The act of becoming shallower.

   “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.”