The Black Sea deluge is a hypothesized catastrophic rise in the level of the Black Sea circa 5600 BC from waters from the Mediterranean Sea breaching a sill in the Bosphorus strait. The hypothesis was headlined when The New York Times published it in December 1996. It was later published in an academic journal in April 1997. While it is agreed that the sequence of events described by the hypothesis occurred, there is significant debate over the suddenness, dating and magnitude of the events. Over geological eras, water has flowed in and out of the Black Sea basin. This hypothesis concerns the occurrence of the last inflow and the primary point of controversy is whether the event was gradual or catastrophic.
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Flood hypothesis
In 1997, William Ryan, Walter Pitman and their colleagues published their hypothesis that a massive flooding of the Black Sea occurred about 5600 BC through the Bosphorus. Before that date, glacial meltwater had turned the Black and Caspian Seas into vast freshwater lakes 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. The levels of the lakes dropped through evaporation, while changes in worldwide hydrology caused overall sea level to rise. The rising Mediterranean finally spilled over a rocky sill at the Bosphorus. 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, "40 km3 (10 cu mi) of water poured through each day, two hundred times the flow of the Niagara Falls. The Bosphorus flume roared and surged at full spate for at least three hundred days."
Further research
Samplings of sediments in the Black Sea by a series of expeditions carried out between 1998 and 2005 in the frame of a European Project ASSEMBLAGE and coordinated by a French oceanographer, Gilles Lericolais, brought some new inputs to the hypothesis. The results were also completed by the Noah Project led by Petko Dimitrov from the Bulgarian Institute of Oceanology (IO-BAS). Furthermore, calculations made by Mark Siddall predicted an underwater canyon that was actually found. A five-year cross-disciplinary research project under the sponsorship of UNESCO and the International Union of Geological Sciences was conducted 2005-9.
Controversy
The brief sensation caused by Ryan and Pitman has turned into an ongoing controversy. Critiques of the deluge hypothesis focus on the magnitude or the rapidity of water level rise or both. With enough blurring of these features the hypothesis is voided. However there are a few salient points to be noted:
- Since the ending of the last glacial period the global sea level has risen some 120 m (390 ft). The process took approximately 10,000 years and abated about 9,000 years ago.
- The flood hypothesis hinges on the geomorphology of the Bosphorus since the end of The Glacial Age. The Black Sea area has been sealed off and reconnected numerous times during the last 500,000 years.
- Various methods have been used to study and date (e.g. sea floor drillings, radiocarbon dating, biological markers) the recent evolution of the Black Sea. The heterogeneous data do not fit into a neat frame, which precludes the confirmation for a sharply defined event.
- The Black Sea flood hypothesis concerns an event supposed to have occurred during the last 10,000-12,000 years with the water level rising rapidly enough to cause easily notable effects.
Criticism
Opponents to the deluge hypothesis point to clues that water has been flowing out of the Black Sea basin as late as 15,000 years ago. The local level must have been higher than the current-then-global level which had already risen from the last glacial minimum. In order to produce a Black Sea flooding such as the one described by Ryan and Pitman a solid obstruction of the Turkish Straits should have occurred. It must have had a significant height to allow for a rise on the south side, while to the north the water level should have been dropping. A notable point here is that the low lands in the Black Sea's basin would have already been flooded.
In this alternative scenario much depends on the evolution of the Bosphorus. According to a study from 2001 the modern sill is 32-34 m (105-112 ft) below sea level, and consists of Quaternary sand over-lying Paleozoic bedrock in which three sills are found at 80-85 m (260-280 ft) below sea level. Sedimentation on these sills started before 10,000 years ago and continued until 5,300 years ago.
A large part of the academic geological community also continues to reject the idea that there could have been enough sustained long-term pressure by water from the Aegean to dig through a supposed isthmus at the present Bosphorus or enough of a difference in water levels (if at all) between the two water basins.
In 2007, a research anthology on the topic was published which makes much of the earlier Russian research available in English for the first time and combines it with more recent scientific findings.
According to a 2009 study by Liviu Giosan, Florin Filip, and Stefan Constatinescu, the level in the Black Sea before the marine reconnection was 30 m (100 ft) below present sea level, rather than the 80 m (260 ft), or lower, of the catastrophe theories. If the flood occurred at all, the sea level increase and the flooded area during the reconnection were significantly smaller than previously proposed. It also occurred earlier than initially surmised, c. 7400 BCE, rather than the originally proposed 5600 BCE. Since the depth of the Bosphorus, in its middle furrow, at present varies from 36 to 124 m (118 to 407 ft), with an average depth of 65 m (213 ft), a calculated stone age shoreline in the Black Sea lying 30 m (100 ft) lower than in the present day would imply that the contact with the Mediterranean may never have been broken during the Holocene, and hence there could have been no sudden waterfall-style transgression.
A February 2009 article reported that the flooding might have been "quite mild".
A 2012 study based on process length variation of the dinoflagellate cyst Lingulodinium machaerophorum shows no evidence for catastrophic flooding.
A 2016 study reviewed the evidence accumulated and reaffirmed the catastrophic scenario (Project: DO02-337 "Ancient coastlines of the Black Sea and conditions for human presence", sponsored by Bulgarian Scientific Fund).
Source of the article : Wikipedia
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