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The Black Sea deluge is a hypothesized catastrophic rise in the level of the Black Sea circa 5600 BC due to waters from the Mediterranean Sea breaching a sill in the Bosporus Strait. The hypothesis made headlines when The New York Times published it in December 1996, shortly before it was published in an academic journal.[1] While it is agreed that the sequence of events described did occur, there is debate over the suddenness and magnitude of the events. Two opposing hypotheses have arisen to explain the rise of the Black Sea: gradual and oscillating[2]:15. The oscillating hypothesis specifies that over the last 30,000 years, water has intermittently flowed back and forth between the Black Sea and Aegean Sea in relatively small magnitudes.


Flood hypothesis

Black Sea today (light blue) and in 5600 BC (dark blue) according to Ryan and Pitman's hypothesis.

In 1997, William Ryan and Walter Pitman published evidence that a massive flooding of the Black Sea occurred about 5600 BC through the Bosporus, following this scenario.[3] Before that date, glacial meltwater had turned the Black and Caspian Seas into vast freshwater lakes which were draining into the Aegean Sea. As glaciers retreated, some of the rivers emptying into the Black Sea declined in volume and changed course to drain into the North Sea.[4] The levels of the lakes dropped through evaporation, while changes in worldwide hydrology caused sea level to rise. The rising Mediterranean finally spilled over a rocky sill at the Bosporus. The event flooded 155,000 km2 (60,000 sq mi) of land and significantly expanded the Black Sea shoreline to the north and west. According to the researchers, "Ten cubic miles [42 km3] of water poured through each day, two hundred times what flows over Niagara Falls. . . . The Bosporus flume roared and surged at full spate for at least three hundred days."

Samplings of sediments in the Black Sea by a series of expeditions carried out between 1998 to 2005 confirmed the conclusion of Pitman and Ryan.[5]; the Noah project led by the Bulgarian Institute of Oceanography (IO-BAS).[6] Furthermore, calculations made by Mark Siddall predicted an underwater canyon that was actually found.[7]


While it is agreed by all that the sequence of events described did occur, there is debate over their suddenness and magnitude. In particular, if the water level of the Black Sea were initially higher, the effect of the spillover would have been much less dramatic.

Countering the hypothesis of Ryan and Pitman are data collected prior to its publication by Ukrainian and Russian scientists including Valentina Yanko-Hombach, who claims that the water flow through the Bosporus repeatedly reversed direction over geological time depending on fluctuation in the levels of the Aegean Sea and the Black Sea. This contradicts the hypothesized catastrophic breakage of a Bosporus sill. Likewise, the water levels calculated by Yanko-Hombach differed widely from those hypothesized by Ryan and Pitman.

In 2007, a research anthology on the topic was published which makes available much of the earlier Russian research in English for the first time, and combines it with more recent scientific findings.[2]

A five year, cross-disciplinary research project under the sponsorship of UNESCO and the International Union of Geological Sciences was conducted 2005-2009.[8]

A February 2009 article reported that the flooding might have been "quite mild".[9]

Evidence from archaeology

Before and after the flood. Source: United States NOAA.

Although neolithic agriculture had by that time already reached the Pannonian plain, Ryan and Pittman link its spread with people displaced by the postulated flood. More recent examinations by oceanographers such as Teofilo A. "Jun" Abrajano Jr. at Rensselaer Polytechnic Institute and his Canadian colleague Ali Aksu of Memorial University of Newfoundland have cast some doubt on this linkage. Abrajano's team, finding sapropel mud deposits in the Sea of Marmara which are today associated with freshwater outflow over top of salt-water inflow, have concluded that there has been sustained fresh water outflow from the Black Sea to the Mediterranean and the Black Sea for at least 10,000 years:[10] Aksu found an underwater delta south of the Bosporus; evidence for a strong flow of fresh water out of the Black Sea in the 8th millennium BC.[11]

In a series of expeditions, a team of marine archeologists led by Robert Ballard identified what appeared to be ancient shorelines, freshwater snail shells, drowned river valleys, tool-worked timbers, and man-made structures in roughly 300 feet (100 m) of water off the Black Sea coast of modern Turkey. Although radiocarbon dating of freshwater mollusk remains indicated an age of about 7,500 years, one should note that radiocarbon dating in freshwater mollusks in particular can be inaccurate.[12] Such inaccuracies, however, are always in the direction of objects appearing older than they actually are (containing less 14C than expected),[12] so the time given is a maximum age of a freshwater shoreline at that location.


  1. ^ NYT 1996
  2. ^ a b Yanko-Hombach et al. 2007
  3. ^ Ryan and Pitman 1997
  4. ^ National Oceanographic and Atmospheric Administration. Climate History: Exploring Climate Events and Human Development"
  5. ^ ASSEMBLAGE—ASSEssMent of the BLAck Sea sedimentary system since the last Glacial Extreme
  6. ^ Dimitrov and Dimitrov 2004
  7. ^ Nature 2004
  8. ^ IGCP 521, Web portal for project data
  9. ^ National Geographic News 2009
  10. ^ Aksu et al. 2002
  11. ^ New Scientist. 2004
  12. ^ a b Keith and Anderson 1963. "Evidence is presented to show that modern mollusk shells from rivers can have anomalous radiocarbon ages, owing mainly to incorporation of inactive (carbon-14-deficient) carbon from humus . . . ."

Works consulted

Further reading

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