I am having a problem with the mechanics of a rapid Black Sea Flood as popularized by Ryan and Pitman and the recent archaeological findings. The Black Sea Basin has the Danube, the Dnieper, the Dniester and the Bug flowing into it, to name just a few. I cannot see how this much water, especially back during the melting of the glaciers, did not fill up the basin (even if it is 2200 meters deep) and flow out through the (at that time) Valley of the Bosphorus. The Bosphorus has a max depth of 120 meters which is just about right on for a river to discharge into the low sea level of the Pleistocene.
If the Black Sea had been a below sea level, enclosed basin, separated from the higher Mediterannean by a Bosphorus isthmus, it would have been at least brackish, maybe not as much as the Caspian, Great Salt Lake and the Dead Sea, but not fresh as the pre-7000 year ago mussels indicate.
If connected to the Mediterranean through the Bosphorus and Dardaneles, the Black Sea would have been 100-120 meters lower during the late Pleistocene. As all of the oceans rose during the period 6000-8000 years ago (7000 years ago is the Black Sea fresh water-salt water mussel transition time), so would the Black Sea. But it could not have been perceived as a flood.
The only “flood” like event I could imagine would be if some massive Eurasian ice dams had been breached and their huge glacial lakes drained into the Black Sea, similar to what occured in the Pacific Northwest. Before and after that fresh water “flood”, there would have been the gradual rise in salty sea level.
If I understand the maps I have seen and the theory correctly, the landmass between the Mediterranean Sea bed (then substantially lower), and the Black Sea [lake] bed was considerably wider than the width now crossed by the Bosporus and the Dardanelles. Under such condition, it is certainly possible that the topography would have precluded an outflow of the Black Sea, especially if the Lake were in equilibrium with the inflowing river waters. To understand the theory, of course, would require reading their discussion of it and analyzing independantly the evidence upon which they support the conclusion of a sudden influx of seawater around 7500 B.C.
According to the book, the chain of events goes something like this:
Around 14,500 BP, the Eurasian ice sheet starts melting back rapidly, producing large quantities of fresh water. The southern margin of the retreating ice sheet is flanked by several enormous fresh water “great lakes” (no longer in existence) that feed rivers such as the Danube, Dnieper, and Dniester; these rivers spill into the area that becomes the Black Sea, first called the New Euxine Lake. (Meltwater also makes its way down the Volga into the Caspian Sea, and then into New Euxine Lake by way of the Don River.) At this time, global sea level (and the maximum level of New Euxine Lake) was approximately 110 meters below modern sea level.
The region that becomes the Bosporus Strait is, at this time, a small river that drains into New Euxine Lake. The only outlet for the lake is apparently through a small drainage that later becomes the River Sakarya in Turkey. The Sea of Marmara at this time is also fresh water, presumably because of the steady supply of fresh water from New Euxine Lake; it drains into the Aegean via the Dardanelles. The easternmost portion of the Aegean is marine.
Around 11,400 BP, there is another pulse of rapid ice sheet melting and fresh water release. However, this pulse of fresh water never makes it to New Euxine Lake, because post-glacial rebound of the land that was formerly at the leading edge of the ice sheet (in front of the great lakes") has created a drainage barrier that directs the new meltwater pulse northward across northeastern Europe. Global sea level rises due to the freshwater influx, but the level of the New Euxine Lake does not. In fact, the much reduced supply of water from the north apparently leads eventually to a slight drop in the level of the lake. Fresh water no longer drains into the Sea of Marmara through the River Sakarya; the river itself reverses direction and now drains into the New Euxine Lake (its headwaters are in the mountains of northern Turkey).
I didn’t see this mentioned in the book, but judging from the maps some minor local uplift of the mountains (from compression along the Anatolian fault) may also have contributed to the changing direction of river flow.
Time passes; ice sheets retreat further. By 7600 BP global sea level was about 15 m below present sea level and the top of the “dam” in the Bosporus area, while the shore of New Euxine Lake were still nearly 110 m below present sea level. The Sea of Marmara is fully marine. Presumably, the first influx of salty water to the New Euxine Lake would have occurred when the Sea of Marmara was high enough to capture the headwaters of the River Bosporus. By the time another 100 years or so had passed, a few meters further increase in global sea level would have begun the flood in earnest. The tremendous water flow apparently scoured out the Bosporus River valley, deepening it considerably.
The time it took to flood the New Euxine Lake and turn it into the Black Sea is the subject of some debate. Ryan and Pitman calculated an increase in lake level of half a foot per day, so that it would have filled in little more than 2 years’ time. Bob Ballard is of the opinion that it took 40 years (not sure why - the National Geographic press releases didn’t clarify ). So while most of the inhabitants around the shore of the Black Sea would not have perceived a sudden “flood,” as if it were a storm surge, they would have seen their coastal homes drowned in relatively short order. The perception of a speedy flooding would have been enhanced by the fact that the original lake shoreline was nearly flat, so that even a small increase in the Black Sea level would have pushed the shoreline back a considerable distance (most obvious in the northwestern corner of the Black Sea; see this link for a map of the flooded shelf area).
So, in a nutshell:
-The Black Sea (or New Euxine Lake) need not have been brackish prior to the flood, because a) it was filled with extremely fresh water to begin with, and b) wasn’t really isolated for all that long (8000 years) in a relatively cool and wet climate that wouldn’t have encouraged high evaporation rates in the lake.
The maximum depth of the Bosporus Strait now reflects the scouring effects of the salt water influx, not the true level of the former river valley. The elevation of the Bosporus really does seem to have been sufficient to “shelter” the Black Sea region from the effects of global sea level rise until the last few meters. Plus the timing of the influx of marine fossils, and the onset of anoxic conditions in the deeper portions of the Black Sea, is quite abrupt and doesn’t reflect gradual change over 1000 years or more.
I saw those photos Ballard took of a collapsed wooden structure on the bottom of the Black Sea, and I have a question. If they are 7000 years old (as yet unconfirmed), how come they weren’t buried by silt? The Black Sea is the terminus for a number of large rivers that presumably deposit huge quantities of silt. One would think that after seven millenia, any artifacts would be buried deep beneath the sea floor.
Can anyone provide any numbers on this? It would seem that an analysis of the rate at which sediment, etc., is deposited should provide some insight as to whether the 7000 year figure is accurate.
The area that Ballard has been investigating is near the modern Turkish port of Sinop, which has a natural harbor. They chose this location to investigate specifically because it would have been protected by influx from the Bosporus by a projection of land, so the site they’ve discovered would also have been largely protected from sedimentation related to the flood.
The major rivers emptying into the Black Sea do carry considerable silt loads (the Danube and Dnieper submarine fans are accumulating sediment at rates of 1.19-2.19 and 1.07-2.03 m per thousand years, respectively*). However, they are on the northern side of the Black Sea, pretty far from the drowned site. Silt can be carried a considerable distance under the appropriate conditions, but most of the rivers’ sediment load would still have dropped out of the water column long before reaching Ballard’s site.
As it happens, sedimentation rates on the sea floor (away from river deltas) can easily be as low as a few millimeters to a few centimeters per thousand years. So the fact that Ballard’s site has little sediment on it is nice, but not necessarily surprising (and really what they were counting on when they chose this spot).
C. Winguth et al., 2000, Upper Quaternary water level history and sedimentation in the northwestern Black Sea: Marine Geology, v. 167, p. 127-146.
). So while most of the inhabitants around the shore of the Black Sea would not have perceived a sudden “flood,” as if it were a storm surge, they would have seen their coastal homes drowned in relatively short order. The perception of a speedy flooding would have been enhanced by the fact that the original lake shoreline was nearly flat, so that even a small increase in the Black Sea level would have pushed the shoreline back a considerable distance (most obvious in the northwestern corner of the Black Sea; see