information:filtering, linguistic:paraphrasing, information:classification
Mediterranean connection during the Holocene

The Black Sea is connected to the World Ocean by a chain of two shallow straits, the Dardanelles and the Bosporus. The Dardanelles is 55 m (180 ft) deep, and the Bosporus is as shallow as 36 m (118 ft). By comparison, at the height of the last ice age, sea levels were more than 100 m (330 ft) lower than they are now.

There is evidence that water levels in the Black Sea were considerably lower at some point during the post-glacial period. Some researchers theorize that the Black Sea had been a landlocked freshwater lake (at least in upper layers) during the last glaciation and for some time after.

In the aftermath of the last glacial period, water levels in the Black Sea and the Aegean Sea rose independently until they were high enough to exchange water. The exact timeline of this development is still subject to debate. One possibility is that the Black Sea filled first, with excess freshwater flowing over the Bosporus sill and eventually into the Mediterranean Sea. There are also catastrophic scenarios, such as the " Black Sea deluge hypothesis " put forward by William Ryan, Walter Pitman and Petko Dimitrov.