Macleod downloaded a computer-generated isometric map of the Black Sea and the Bosporus.
“The relationship between the Mediterranean and the Black Sea is a kind of microcosm of the Atlantic and the Mediterranean,” he explained. “The Bosporus is only about one hundred metres deep. Any lowering of the Mediterranean below that depth and it becomes a land bridge, cutting off the Black Sea. These were the conditions that allowed the first hominids in Europe to cross over from Asia.” He moved the cursor to highlight three river systems leading into the sea.
“When the Bosporus was a land bridge, evaporation caused the Black Sea to lower, just like the Mediterranean in the salinity crisis. But the Black Sea was replenished by river inflow, from the Danube, the Dnieper and the Don. A median was reached where the rate of evaporation equalled the rate of inflow, and from then on the change was in salinity, with the Black Sea eventually becoming a vast freshwater lake.”
He punched a key and the computer began to simulate the events he had been describing, showing the Bosporus becoming dry and the Black Sea lowering to a point about 150 metres below present sea level and 50 metres below the floor of the Bosporus, where its level was maintained by inflow from the rivers.
He swivelled round and looked at the others.
“Now for the surprise. This is not an image from the early Pleistocene, from the depths of the Ice Age. What you’re looking at is the Black Sea less than ten thousand years ago.”
Katya looked dumbfounded. “You mean after the Ice Age?”
Macleod nodded vigorously. “The most recent glaciation peaked about twenty thousand years ago. We believe the Black Sea was cut off some time before that and had already dropped to the hundred and fifty metre contour. Our beach was the seashore for the next twelve thousand years.”
“Then what happened?”
“It recapitulates the Messinian salinity crisis. The glaciers melt, the Mediterranean rises, water cascades over the Bosporus. The immediate cause may have been a retreat phase some seven thousand years ago in the West Antarctic Ice Sheet. We believe it took only a year for the Black Sea to reach its present level. At full flow almost twenty cubic kilometres poured in daily, resulting in a rise of up to forty centimetres a day or two to three metres a week.”
Jack pointed at the lower part of the map. “Could you give us a close-up of this?”
“Certainly.” Macleod tapped a sequence and the screen zoomed in on the coast of northern Turkey. The isometric terrain mapper continued to depict the topography of the land before the inundation.
Jack edged forward as he spoke. “We’re currently eleven nautical miles off the north coast of Turkey, say eighteen kilometres, and the depth of the sea below us is about one hundred and fifty metres. A constant gradient to the present seashore would mean a rise of about ten metres for every kilometre and a half inland, say a ratio of one to one hundred and fifty. That’s a pretty shallow slope, hardly noticeable. If the sea rose as quickly as you indicate, then we’re looking at three or four hundred metres being flooded inland every week, say fifty metres a day.”
“Or even more,” Macleod said. “Before the inundation, much of what lies beneath us was only a few metres above sea level, with a sharper gradient close to the present shoreline as you begin to ascend the Anatolian Plateau. Within weeks huge areas would have been swamped.”
Jack looked at the map in silence for a few moments. “We’re talking about the early Neolithic, the first period of farming,” he mused. “What would conditions have been like here?”
Macleod beamed. “I’ve had our palaeoclimatologists working overtime on that one. They’ve run a series of simulations with all possible variables to reconstruct the environment between the end of the Pleistocene and the inundation.”
“And?”
“They believe this was the most fertile region in the entire Near East.”
Katya let out a low whistle. “It could be an entirely new tapestry of human history. A strip of coast twenty kilometres wide, hundreds of kilometres long, in one of the key areas for the development of civilization. And never before explored by archaeologists.”
Macleod was twitching with excitement. “And now the reason you’re here. It’s time to return to the ROV monitor.”
The seabed was now more undulating, with occasional rocky outcrops and furrowed depressions where there had once been ravines and river valleys. The depth gauge showed the ROV was over the submerged land surface, some fifteen metres shallower and a kilometre inland from the ancient shoreline. The GPS co-ordinates were beginning to converge with the target figures programmed in by Macleod.
“The Black Sea should be an archaeologists’ paradise,” Jack said. “The upper hundred metres are low in salt, a relic of the freshwater lake and a result of river inflow. Marine borers such as the shipworm Teredo navalis require a more saline environment, so ancient timbers can survive here in pristine condition. It’s always been a dream of mine to find a trireme, an ancient oared warship.”
“But it’s a biologist’s nightmare,” Macleod countered. “Below a hundred metres it’s poisoned with hydrogen sulphide, a result of the chemical alteration of seawater as bacteria use it to digest the huge quantities of organic matter that come in with the rivers. And the abyssal depths are even worse. When the high-saline waters of the Mediterranean cascaded over the Bosporus they sank almost two thousand metres to the deepest part of the sea. It’s still there, a stagnant layer two hundred metres thick, unable to support any life. One of the world’s most noxious environments.”
“At the Izmir NATO base I interrogated a submariner who had defected from the Soviet Black Sea Fleet,” Costas murmured. “An engineer who had worked on their top-secret deep-sea probes. He claimed to have seen shipwrecks standing proud of the seabed with their rigging intact. He showed me a picture where you could even make out human corpses, a jumble of spectral forms encased in brine. It’s one of the spookiest things I’ve ever seen.”
“Almost as remarkable as this.”
A red light flashed in the lower right corner of the screen as the GPS fix converged. Almost simultaneously the seabed transformed into a scene so extraordinary it took their breath away. Directly in front of the ROV the floodlight reflected off a complex of low-set buildings, their flat roofs merging into each other like an Indian pueblo. Ladders connected lower and upper rooms. Everything was shrouded in a ghostly layer of silt like the ash from a volcanic eruption. It was a haunting and desolate image, yet one which made their hearts race with excitement.
“Fantastic,” Jack exclaimed. “Can we take a closer look?”
“I’ll put us where we were when I called you yesterday.”
Macleod switched to manual and jetted the ROV towards an entrance in one of the rooftops. By gingerly feathering the joystick he moved inside, slowly panning the camera round the walls. They were decorated with moulded designs just visible in the gloom, long-necked ungulates, ibexes perhaps, as well as lions and tigers bounding along with outstretched limbs.
“Hydraulic mortar,” Costas murmured.
“What?” Jack asked distractedly.
“It’s the only way those walls can have survived underwater. The mixture must include a hydraulic binding agent. They had access to volcanic dust.”
At the far end of the submerged room was a form instantly recognizable to any student of prehistory. It was the U-shape of a bull’s horns, a larger than life carving embedded in a wide plinth like an altar.
“It’s early Neolithic. No question about it.” Jack was ebullient, his attention completely focused on the extraordinary images in front of them. “This is a household shrine, exactly like one excavated more than thirty years ago at Çatal Hüyük.”