Black Sea deluge hypothesis

300px|thumb|Map of the Black Sea

The Black Sea deluge is the best known of three hypothetical flood scenarios for the Late Quaternary history of the Black Sea that have been proposed since 1997. One other flood scenario proposes a rapid, even catastrophic, rise in sea level of the Black Sea. The hypothesis is controversial, with other authors arguing for a more gradual inundation of the Black Sea.

As proposed, the Early Holocene Black Sea flood scenario describes events that would have profoundly affected prehistoric settlement in Eastern Europe and adjacent parts of Asia and possibly was the basis of oral history concerning the myth of Noah's flood. In 2003, Ryan and coauthors revised the dating of the early Holocene flood to 8,800 years ago, .

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 global sea levels to rise. and later published as a book. In a series of expeditions widely covered by mainstream media, a team of marine archaeologists 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 of water off the Black Sea coast of modern Turkey.

Late Pleistocene Great Flood hypothesis

In 2003 and 2007, a more ancient catastrophic flood scenario was proposed by Andrei L. Chepalyga for the Late Quaternary sea level rise of the Black Sea. the non-catastrophic progressive flood model (or gradual inflow model) has been proposed to explain the Late Quaternary sea level history of the Black Sea.

About 8,000 years ago, the level of the Marmara Sea would have risen high enough for two-way flow to start. The evidence used to support this scenario includes the disparate ages of sapropel deposition in the eastern Mediterranean Sea and Black Sea; buried back-stepping barrier islands observed on the Black Sea shelf; and an under-water delta in the Marmara Sea, near the Bosporus Strait, composed of Black Sea sediments.

Counter-arguments

thumb|upright=1.3|Sea levels since the [[Last Glacial Maximum, c. 20 kya]]

Criticisms of the deluge hypothesis hinge on two main lines of arguments. The first mainly focuses on the water level of the Black Sea: if the magnitude and pace of the rise of the Black Sea level was moderate enough, or if it even outpaced the rise in the Aegean basin (with water flowing, when they reconnected, from the former to the latter as it does now), or if the straits were already opened (at a lower level than now) and the two basins already connected at the time of the hypothesised flood, the catastrophe hypothesis is voided. The second is the lack of archaeological evidence one would expect of a flood, such as impact on geology, wildlife or humans.

Since the end of the last glacial period, the global sea level has risen . The flood hypothesis hinges on the geomorphology of the Bosporus since the end of the glacial age. The Black Sea area has been isolated and reconnected many times during the last 500,000 years.

Opponents of the deluge hypothesis point to clues that water was flowing out of the Black Sea basin as late as 15,000 years ago.

In this alternative scenario, much depends on the evolution of the Bosporus. According to a study from 2001, the modern sill is below sea level and consists of Quaternary sand over-lying Paleozoic bedrock in which three sills are found at 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 Bosporus or enough of a difference in water levels, if any, between the two water basins.

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

The level in the Black Sea before the marine reconnection was estimated to have been below present sea level, rather than of the catastrophe theories or even lower; if the flood occurred at all, the sea level increase and the flooded area during the reconnection were significantly smaller than previously proposed. Since the depth of the Bosporus, in its middle furrow, at present varies from , with an average depth of , a calculated Stone Age shoreline in the Black Sea lying lower than in the present day would imply that the contact with the Mediterranean might never have been broken during the Holocene, and hence there could have been no sudden waterfall-style transgression. The flooding could have been "not so big".

In 2011, several authors concluded that "there is no underwater archaeological evidence to support any catastrophic submergence of prehistoric Black Sea settlements during the late Pleistocene or early Holocene intervals".

A 2012 study based on process length variation of the dinoflagellate cyst Lingulodinium machaerophorum shows no evidence for catastrophic flooding.

However, Geophysical, geochronological, and geochemical evidence points to a "fast transgression" of the submergence lasting between 10 and 200 years.

A 2022 literature review concluded that there was insufficient evidence for a flood scenario. It was more likely that the waters of the Black Sea itself gradually outflowed to the Mediterranean. There was also no archaeological evidence of humans evacuating the area during the relevant time.

Black Sea deluge hypothesis

Late Pleistocene Great Flood hypothesis

Counter-arguments

See also

References

Further reading