The Black Sea deluge theory was proposed by Columbia University geologists William Ryan and Walter Pitman in the 1990s, when the men believed they found evidence of a massive flood into the Black Sea sometime around 7500 B.C. Their theory expounds upon how the Black Sea formed after a shallow lake was inundated by the Mediterranean Sea due to warming temperatures and rising sea levels.
Pitman and Ryan's 1998 book "Noah's Flood" reveals the geologists believe the Black Sea was a landlocked, shallow lake in a fertile plain surrounded by numerous river valleys. At some point, the Mediterranean Sea overtopped the Bosphorus and flooded the Black Sea at a rate of 6inches per day, causing saltwater to decimate the farming area. The theory goes that this flood terrorized residents so much that the Noah's flood was created as a story about God's wrath.
Oceanographer Robert Ballard led a team to explore the Black Sea in 1999, and his findings revealed extinct freshwater mollusks and species of saltwater mollusks that once inhabited the body of water. The original shoreline of the freshwater lake was located, and signs of Neolithic settlements were also discovered, lending credence to the theory that the Black Sea was once a thriving agricultural center.
A study in 2009 explained that the Black Sea's level did rise in 7,500 B.C., but only about 30 feet, not 180 feet. About 772 square miles of farm land flooded as a result.