Romania, 20,000 Years Ago

I · The sea

A lake a hundred metres lower

The Black Sea of 20,000 years ago was a lake of nearly fresh water, standing about 105 metres below today's level, cut off from the Mediterranean by a sill at the Bosphorus that the water no longer reached. The whole north-western shelf lay exposed: a plain of loess and sand of more than 40,000 square kilometres between Varna and Odesa, two and a half times today's Dobrogea. The site of Constanța was 87 kilometres from the shore. Mangalia, 60. Sulina, which now has the sea in front of it, 117.

The Danube had no delta. It passed the site of Tulcea and ran another 210 kilometres or so across the exposed plain to the edge of the shelf, where it plunged into the Viteaz canyon towards the basin floor more than 2,000 metres down. On the map that course is computed: it is the lowest route through today's seabed relief from the head of the delta to the head of the canyon. The Viteaz canyon is still there in the bathymetry, a V-shaped cut 2.5 to 4 kilometres wide, and in lowstand periods the river fed it directly.

The water came in two waves. The first, between 16,500 and 13,000 years ago, filled the lake up to the Bosphorus sill, about 37 metres below today's level, with meltwater from the northern ice sheets. Then, in the cold of the Younger Dryas, the level fell again; by how much, the authors disagree, and the reconstructions differ by tens of metres. The map follows a middle path, with a fall to 80 metres below today's level 10,000 years ago. Salt water only came in about 8,400 years ago, once the ocean had risen above the Bosphorus sill; strontium isotopes in shells date it. From then on, the level of the lake turned sea followed the world ocean.

The delta is the youngest thing on the map. The first lobe, on the old Danube branch, began filling the bay at Tulcea about 7,500 years ago; the delta plain we know began building out to sea 5,200 years ago. For 5,000 years the sea at the Danube mouth has stayed between a metre and a half above and two metres below today's level, which let the delta grow almost without interruption.

II · The ice

Glaciers down to a thousand metres

In the Retezat, glaciers reached their greatest extent about 21,000 years ago, in step with the global Last Glacial Maximum. Tongues of ice came down the Pietrele valley to 1,000 or 1,050 metres, the glacier complex covered 27.3 square kilometres, and the equilibrium line, the altitude above which more snow accumulates than melts, stood at 1,646 metres. Exposure ages of moraine boulders, measured with beryllium-10, show two readvances during the retreat, 18,600 and 16,300 years ago.

In the Făgăraș, the same measurements give a stage at 18,700 years, a cirque-glacier stage at 14,500 and the last glacierets, in the hollows below the ridge, 13,300 years ago, with a margin of 1,200. After that the Carpathians had no permanent ice. On the map, ice appears on everything above the equilibrium line of the moment, wind-swept summits included, which in reality stayed bare while the glaciers sat in the valleys. The terrain used has cells of about a kilometre, so the peaks come out lower than they are: Moldoveanu is 2,544 metres high and 2,210 in the grid. The area above the 1,650-metre line in the Romanian Carpathians is about 2,100 square kilometres; it is an upper bound on the ice.

III · The forest

Cold steppe and the refugia of trees

The plains of 20,000 years ago were cold steppe with tundra elements, wind-swept and blanketed with the dust that became the loess of the Bărăgan and Dobrogea. Pollen-based reconstructions for central and eastern Europe give, for the glacial maximum, a mean annual temperature roughly ten degrees below today's. The trees did not vanish, though. Pine, larch, spruce, birch, alder and poplar held out in sheltered valleys and on the hills at the foot of the Carpathians, and pollen from before 14,700 years ago shows that some warmth-loving broadleaves also sat out that winter in microrefugia. Romania was one of the places from which Europe's forest set off north again.

The warming of 14,700 years ago brought groves of birch and pine to the plain; the Younger Dryas cooling, between 12,900 and 11,700 years ago, pushed them back; and the start of the Holocene finally let them climb. Spruce and pine took the mountains, oak, elm and lime came down from their refugia into the plain, and beech, which gives the hills their present face, only spread about 5,100 years ago. On the map, vegetation is a scheme by altitude, with bands that move in time at these moments; it is drawn to show the direction of change at the scale of the region. Over the last 8,000 years the plain opens up gradually as the plough claims it.

IV · The people

People were already here

Twenty thousand years before the clock starts, people like us already lived in Peștera cu Oase, near Anina: the Oase 1 jaw is between 38,400 and 42,500 years old and is the oldest directly dated modern human in Europe. At Coliboaia, in the Apuseni, the charcoal drawings on the walls are between 32,000 and 36,000 years old. At the glacial maximum, when the map sits at its cold end, a camp of Gravettian hunters at Poiana Cireșului, near Piatra Neamț, left the site's richest occupation layer, dated between 20,150 and 19,450 years ago, with a bone whistle and engraved pendants. People were few and mobile, and precisely dated sites are rare, so the dots on the map show only the places where we know for certain someone stood.

At the Iron Gates, at Schela Cladovei, fishing communities lived on the Danube bank for thousands of years; the Mesolithic burials are between 8,570 and 8,290 years old. The first farmers, with the Starčevo-Criș culture, appear in the Banat and Transylvania about 8,000 years ago, around 6000 BC. Cucuteni paints its pots between 4800 and 3500 BC. The Greeks raise Histria on the shore of a lagoon in 657 BC, and the Dacians make their capital at Sarmizegetusa Regia a century before the Roman conquest. The last two thousand years, with everything we know from books, take up a tenth of the clock's 20,000 years.

V · The animals

Those who left and those who came back

The cave bear, whose bones fill the caves of the Apuseni and the Southern Carpathians, was already gone: the last radiocarbon dates put it between 26,100 and 24,300 years ago, 4,000 years before the clock starts. The woolly mammoth, the woolly rhinoceros and the cave lion outlast the glacial maximum and perish with the warming, about 14,000 years ago, as their steppe turns into forest. The giant deer, with antlers three and a half metres across, disappears from central Europe 12,000 years ago and holds on in western Siberia until 7,700.

The rest of the disappearing was done by people, and it is recent. The world's last aurochs, a female, died in 1627, in Poland. The last free tarpan was caught in the Ukrainian steppe in 1879. The European bison, which stood on the coat of arms of Moldavia, was last killed in Moldavia in 1762 and in Transylvania in 1790; it was brought back in 1958, at Hațeg, with a pair from Poland. The beaver was last killed in 1823 and brought back in 1998, on the Olt, from where it made its own way down to the delta. On the clock, those two returns are the only lines that light up again.

VI · Your town

What the clock computes for your place

The terrain comes from NOAA's global elevation and bathymetry mosaic, built on ETOPO 2022, extracted at 30 arc-seconds, cells of roughly a kilometre by 700 metres, on a rectangle from Belgrade to Crimea. For every cell a flood level was computed: the lowest water level at which the cell connects to the deep Black Sea basin. A valley below the water level but closed off by a sill therefore stays dry, and the shoreline at any moment is a consequence of the relief and the level curve. The distance to the sea for your town is the distance to the nearest flooded cell at the level of the moment; "today" uses level zero. The places come from GeoNames, 18,214 localities in Romania and the Republic of Moldova.

The curve of the lake, then sea, level is an interpolation between published anchors: −105 metres at the glacial maximum, the rise to the Bosphorus sill at −37 metres between 16,500 and 13,000 years ago, the Younger Dryas fall, the arrival of salt water 8,400 years ago and then the world ocean. The glacier equilibrium line starts at 1,650 metres and rises with the exposure ages from the Retezat and Făgăraș until it clears the ridges, 13,300 years ago. The treeline and the state of lowland vegetation are schematic and follow the cited pollen syntheses. The temperature shown is an approximation of the mean annual cooling in reconstructions for central and eastern Europe. The distance figures for Constanța change little with the level chosen, because the shelf edge is steep: at −80 metres it is 79 kilometres, at −105 it is 87, at −120 it is 88.

Sources

Sources