Birth of the Black Sea

It was back in 1936 when Dr. Thornwell Jacobs of Oglethorpe University had his great idea.  He wanted to revive the ancient practice of burying artifacts in tombs, but add a modern spin.  His idea was to create a large (20 x 10 x 10) treasure vault and fill it with the artifacts of his own time for later generations to open.  Having a miserable ear for the sound of English, he called his device a crypt.  It later became something of a twentieth century fad under the friendlier title of time capsule.

Still, the good doctor’s vision was certainly not shortsighted.  According to his schedule, his crypt is not due to be opened until 8113 CE, which is practically measurement on a geological scale.  Of course, it is pretty rare in the geological world to be able to establish any event with such precision.  In fact, I can think of exactly one.

So let me tell you about it.

The end of the last Ice Age was not an abrupt thing.  From about 20,000 years ago up to around 8,000 years ago, geologists have mapped a more or less gradual rise in the sea level.  As all that ice melted, it fed ancient rivers, which gave the water back to the world’s oceans.  But it was not just the saline waters that were rising.  Some of those rivers flowed into ancient lake beds, causing them to fill as well.

One of these ancient lakes was located above the eastern end of the Mediterranean basin.  As all that melt water raised the level of the Mediterranean Sea, the deep chasm of the bed was filling, too.  Over the millennia, it became a lake, filled with freshwater fish.  Eventually its shores attracted groups of Neolithic humans.  The water level was still rising, fed by the rivers, but it was pretty slow.

Unfortunately, the Mediterranean was rising just a bit faster.  A little less than 7,500 years ago, the Mediterranean had risen until it was about 150 meters higher than the inland lake.  Pretty soon (according to many samples of archaeological dating, it was exactly 7,150 years ago), the Mediterranean finally rose to the point that it overflowed the last land separating the two, and the salt water began to trickle into the lake.

Water and gravity being what they are, the trickle pretty quickly became a stream, then a river, then a great big river.  The erosion track from the rushing salt water can still be detected at the bottom of the channel.  In what was, in geological terms, an instantaneous event, the depth of what was to be called the Black Sea rose 150 meters while its surface area grew by 150,000 km2.

What, exactly, was “instantaneous?”

Estimates vary, but it was fast, with the water level rising perhaps as much as 6 inches a day.  From the point of view of the freshwater species in the lake, the change to saltwater was much too fast to adapt to.  Core samples taken all around the Sea show that all the fresh water species simply died in that single geological moment, replaced by salt water types with no transition period at all.

But from a human point of view, a change of six inches per day, or twelve, or whatever, is pretty slow.  Slow enough, at least, that you had to be pretty stupid to be caught in the “flood.”  Instead, the human beings presumably moved up a bit higher to dry land, then a bit higher, then a bit higher still.  Eventually, they must have become convinced that the rise was never going to stop.  At that point everyone probably scattered in all directions:  to other settlements up the rivers, north to join the tribes on the steppes, or southeastward towards what we would later call the Near East.

The times were prehistoric, but hardly pre-verbal.  One can imagine them trying to explain to their new neighbors all about the catastrophe that had overtaken them.  Most, if not all of them, would have been far too distant from the Bosporus (that flood channel) to have any idea that a great salt water river had suddenly appeared.  Instead, about all they knew was that the waters inexplicably rose, and the land was drowned.

I say “inexplicably,” but human beings hate to leave things like that.  Instead, we make up stories to explain events that are out of our control.  One can imagine that they, or their new neighbors, quickly figured out that, a) the gods had become really pissed at the lake dwellers and, b) since floods were caused by rains from heaven, the gods must have caused one heck of a rain storm somewhere to flood everyone out.

In time, it would have passed into legend.

So today there are lots of folks in the archaeological world who believe that it was this event, communicated eastward to the Fertile Crescent, that was the origin of the Flood in the Gilgamesh epic.  And most contemporary Biblical scholars trace the origin of the Biblical Flood narrative back to Gilgamesh.

All of which is pretty cool…but it’s not what I wanted to talk about.  I want to talk about the Black Sea itself.  Because it has a peculiarity that has recently revealed some pretty miraculous consequences.

If you were to sail out into the Black Sea and drop a deepwater net over the side, when you raised the net it would be quite empty of fish, but it would smell abominably of hydrogen sulfide (rotten eggs).

Why?  [I have to warn you that what immediately follows is technically fascinating…if you happen to be a total nerd with no real life at all.  But bear with me, I promise there is something really good hiding at the end.]

The reason that you would catch no fish in your net is that, below 200 meters, the Black Sea has no life higher than microorganisms.  It is simply dead.  Considering that its depth reaches a whopping 2210 meters, that means there is one heck of a lot of dead water.  The biological fact is that, from that 200 meter line all the way down to the bottom, the Black Sea is anoxic.  In fact, it is the largest anoxic marine system in the world.  From that, it is quite simple:  no oxygen, no higher organisms.

The cause seems to be that there are no deepwater currents in the Black Sea.  It is estimated that there is a full exchange of water from the depths roughly every 1,000 years!  But the upper levels of the Sea (above the 100 meter line) are rich in life.  So those upper levels are constantly breeding and then depositing organic matter that falls down into the lower depths.  There it decays, the process consuming all the available oxygen.  What remains is a smelly, slimy gunk called sapropel, populated only with microorganisms that live by breaking down sulfates into hydrogen sulfide.

The next factoid in our story concerns the fate of wood in the oceans:  it gets eaten.  Mostly it is consumed by members of a large family of mollusks called shipworms.  They look like worms (typically around a centimeter across by many centimeters long) although they are, in fact, bivalves.  But, not having hard bivalve shells to protect their soft parts, they need a housing.  They get this by having a neat flexibility in their diet: they can both eat their way into wood and also filter feed.  They like to live in colonies and their appetite is voracious.  They can reduce huge pieces of timber into pieces of Swiss cheese in a matter of months.

Archaeologists know about their appetite to their sorrow.  Any ship that is wrecked and not immediately sealed in mud disappears.  Which is why we know a great deal about Roman amphorae (i.e. the cargo) and surprisingly little about the details of how their ships were constructed, how big they really were, how they were rigged, etc.  Similar ignorance prevails about Greek ships, Phoenician ships, Medieval ships, and so on.  If the pictures we find on jars, inscriptions, and paintings don’t show a detail or show it incorrectly, we have no way of knowing about it.

But maybe now we will.

It would be hard to find a body of water that has had more traffic of various kinds over the centuries than the Black Sea.  Phoenicians traded there, the Romans controlled it for a while, the Greeks treated it like a wholly owned subsidiary both before and after the Romans, it was the Byzantines’ lake, the Turks’ back yard, and a battleground between the Russians on one side and the British, Turks, and French on the other.

A few years back some archaeologists got to contemplating two facts about the Black Sea: a) just about every imaginable kind of ship probably sank there; b) shipworms cannot live in its anoxic depths.  These led them to theorize that, if we could go deep enough, we might be able to find, virtually intact, samples of every kind of ship that had ever sailed there.  Over the last few years Robert Ballard, of Titanic fame, has run a couple of expeditions to test the theory.

And it’s true.

Using side scan radar and his usual camera robots, in 2000 Ballard found a wreck at roughly 300 meters – solidly in the anoxic zone.  It was mostly submerged in mud, but sticking right out are intact spars and ribs. The contrast between this wreck with its wood and the usual naked piles of amphorae is impressive.  But, as a stunning measure of exactly how intact some of these wrecks might prove to be, at the top of the mast (sticking up 11 meters) is a clearly visible loop of halyard rope.  Accelerator Mass Spectrometry (AMS) dating puts the wreck at 410 – 520 CE.  I.e, the wreck is Byzantine.  So that rope has been waiting down there for 1500 years.  It’s just staggering!  And that wreck is just the start.  It looks as if there is an unimaginable wealth of perfectly preserved history waiting to be discovered.

It fairly boggles the mind.

As in most human endeavors, there is also a dose of irony here.  We are an interesting species, curious, but somewhat lacking in a sense of perspective.  We like to make things big…in our own eyes.  We built the pyramids and other monuments to our vanity and as a way of preserving ourselves.  In modern times, Dr. Jacobs created his swimming pool-sized time capsule with much the same goals.

And then we find out the Black Sea is itself one gigantic time capsule.  I know it’s not a contest and it may sound theologically unsound, but it almost seems as if God is saying, “Neener, Neener, Neener!”

Leave a Reply

Your email address will not be published. Required fields are marked *