Scientists have reconstructed in detail the history of the largest lake on Earth - Paratethys, which covered Central Asia, southern Russia and reached the Alps. It was home to dwarf dolphins and whales, and an amazing megafauna reigned on the coast, which later moved to Africa. Several million years ago, the giant body of water disappeared, which caused an ecological disaster.
Ocean Heritage Tethys
In the Mesozoic, 200 million years ago, all continents united into two giant supercontinent: Gondwana in the Southern Hemisphere and Laurasia in the Northern. The paleo-ocean splashed between them, which the Austrian geologist Eduard Suess named Tethys in 1893 after the Greek goddess Thephis.
As Gondwana disintegrated, Tethys shrank until it became a narrow inland sea stretching from the Atlantic coast of present-day Spain and Morocco to Central Asia. In the Middle Miocene, about 12 million years ago, the plates collided, which led to the rise of mountains in Central Europe and the division of the Tethys Ocean into two bodies of water. In the west, the Mediterranean Sea was formed, in the east - a huge lake - Paratethys.
The greatness and decline of Paratethys
Geologists have recently reconstructed in detail the history of Paratethys for 12 million years. It turned out that the mega-lake several times overflowed, then almost completely disappeared. The water level in a closed reservoir was completely dependent on the rivers flowing into it, and their high flow changed with the climate.
During periods of maximum flooding, the lake occupied the territory from the Carpathians to Kazakhstan with the islands of Crimea and the Caucasus in the middle. There was more of the modern Mediterranean Sea - about 2.8 million square kilometers - and 80 meters above the current sea level. It contained up to 1.77 million cubic kilometers of water, which is more than ten times the volume of all today's freshwater and salt lakes in the world combined. When the water receded, only two reservoirs remained - in the place of the central basin of the Black Sea and the southern part of the Caspian.
Scientists have found that 7, 65-7, 9 million years ago, during the so-called Great Kherson drought, the level of Paratethys fell by 250 meters, the south of Ukraine, the steppe Crimea, the North Caucasus and the Stavropol Upland came out of the water, the Terek Strait dried up to North Caucasus, connecting the Black and Caspian Seas. As a result, the first turned into a freshwater Pontic lake-sea, and in the place of the southern Caspian the Balakhan Lake was formed.
Four million years ago, the water rose again, the Black Sea again merged with the Caspian Sea. A single basin, covering the Black Sea, the Caspian Sea, the lower Volga region and the territory between the Caspian and Aral seas, existed for quite a long time and disintegrated only 500-300 thousand years ago.
Maximum (blue) and minimum (blue) areas of Paratethys in the Miocene
Homeland of elephants
A unique animal world has developed in the mega-lake. There were the smallest baleen whales on the planet - cetotheria, about two meters long. Interestingly, many of the whales, dolphins and seals that lived in Paratethys were miniature. According to biologists, this is how animals adapted to the constantly changing size of the reservoir.
Special conditions have developed on the shores of Paratethys. As the water level of the mega-lake fell, the coastlines turned into meadows rich in plant food - "hot spots" of evolution.
A recently published article on the formation of modern African fauna proves that many of the mammal species that inhabit the African savannah today, including antelopes, elephants and giraffes, originated on the southern coast of Paratethys, in what is now western Iran.
The lake that filled the sea
A key event in the history of the largest lake on Earth took place about six million years ago. Continuing plate movements have lifted mountains in the western Mediterranean. At the same time, the level of the World Ocean dropped sharply, by 100-120 meters, due to the growth of glaciers in the Northern Hemisphere. As a result, the Mediterranean Sea was cut off from the Atlantic and for several millennia it almost completely dried up - only three or four highly saline lakes remained, into which large rivers flowed. In paleogeography, this is called the Messinian salinity crisis.
In the neighboring Paratethys, on the contrary, the water rose due to the growth of the Caucasus Mountains. At some point, the lake broke through a bridge in the Bosphorus region and collapsed from a height of 200-250 meters into the dry basin of the Mediterranean Sea. And only separate fragments remained of Paratethys - the Black, Azov, Caspian seas, the already dried Aral Sea, as well as several lakes, such as Urmia and Deryacheye-Nemek in Iran.
The area between the Caspian and Aral seas. In the center is the Ustyurt plateau. NASA satellite image, December 8, 2001
The Caspian steppes and the area between the Caspian and Aral seas are the bottom of an ancient reservoir that has hardly changed. This is especially clearly seen on the Ustyurt plateau, in the west of Central Asia: an absolutely flat, cracked plain with towering outcrops of former islands.