Page "Bosphorus" Paragraph 7

The exact cause for the formation of the Bosphorus remains the subject of vigorous debate among geologists.

Thousands of years ago, the Black Sea became disconnected from the Aegean Sea.

The Black Sea deluge theory ( published in 1997 by William Ryan and Walter Pitman from Columbia University ) contends that the Bosphorus was formed about 5600 BC when the rising waters of the Mediterranean / Sea of Marmara breached through to the Black Sea, which at the time ( according to the theory ) was a low-lying body of fresh water.