History of Black Sea

About 50-60 million years ago, before the beginning of Tertiary Period, large oceanic basin stretched out from west to east across Southern Europe and Central Asia connecting the Atlantic Ocean and the Pacific Ocean. It was the salty Tethys Sea. As a result of crust upheaval, in the middle of Tertiary Period, the Tethys Sea had become separated first from Pacific Ocean and later from the Atlantic.

 

Major crust movements caused mountain-building and they formatted the Alps, The Carpathians, the Balkan Mountains and the Caucasus Mountain. In result of upheaval the Tethys Sea shrunk in size and became divided into a number of brackish basins. One of them, the Sarmatic Sea, stretched out from the present location of Vienna to the foothills of Tien Shan Mountains and included modern Black Sea, the Azov Sea, the Caspian Sea and Aral Sea. The Sarmatic Sea was separated from the ocean, and gradually its salinity fell as a result of the inflow from rivers. It is interesting to note that typically oceanic animals, such as whales, manatees and seals, continued to inhabit the Sarmatic Sea for long time, before they also disappeared.

 

By the late Miocene and early Pliocene (3-5 million years ago) the Sarmatic Sea had shrunk to the size of Maeotic Sea. During that period a link to the ocean was again established, salinity increased and marine species of plants and animals settled in the sea.

 

In the Pliocene (about 1.5-3 million years ago) the connection with the ocean was again served, and the salty Maeotic Sea was replaced by the almost freshwater Pontian Sea-Lake. Within it the future Black and Caspian Seas were connected through the present-day northern Caucasus. In the late Porian stage the Earth's crust began to rise in the northern Caucasus, gradually isolating the Caspian Sea from the basin. From that period onwards the Caspian Sea, on one hand, and the Black sea and Azov Sea, on another, went their separate ways, although temporary links between them were formed from time to time.

 

With the onset of the Quarternaty Period and the Ice Age the salinity and species composition of the developing Black Sea continued to change, as did the outline of the sea. By the late Pliocene (less than one million years ago) the Pontian Sea-Lake had shrunk to the size of the Chaudian Sea-Lake.

 

When the ice began to melt in late Mindel (Elsterian) Glaciation (some 400,000-500,000 years ago), the Chaudian Sea-Lakebecame filled with melt waters and turned into the Paleoexinian basin. Its outline resembled the modern Black Sea and the Azov Sea. In the Northeast it was connected to the Caspian Sea through the Kumo-Manych depression, and in the Southwest to the Sea of Marmara through the Bosphorus. At the time, the Sea of Marmara was isolated from the Mediterranean and was also greatly affected by reduced salinity.

 

The Riss-Wurm Interglacian Period (100,000-150,000 years ago) heralded a new period in the history of the Black Sea. Following the opening of the Dardanelles for the first time since the formation of the Tethys Sea, the future Black Sea became connected to the Mediterranean and the World Ocean. The so-called Karagat Basin or Karagat Sea was formed, with a salinity higher than that of the modern Black Sea. Various representatives of marine flora and fauna were introduced into it together with ocean water. They occupied a larger part of the basin, forcing the brackish water and Pontian species into bays, limans and river estuaries salinity. However, that basin too was to undergo changes.

 

Some 18,000-20,000 years ago the Karangat Sea was replaced by the Neoeuxinian Lake-Sea. This coincided with the last Wurm Glaciation. The sea was filled with melting waters. Once again it lost its connection to the ocean and its salinity was greatly reduced. The holophilic oceanic flora and fauna also disappeared, while the Pontian species that had survived the difficult Karangat period in limans and river estuaries came out of hiding and yet again occupied the entire sea.

 

After approximately 10,000 years the basin entered its current phase and the modern Black Sea was formed. In fact, the word "modern" in this case does not mean that the sea was identical to what it is today. In the beginning about 7,000 years ago, (although some experts believe that it was even later, about 5,000 years ago) a connection to the Mediterranean and the World Ocean was established through the Bosphorus and the Dardanells. A gradual salinisation of the Black Sea followed and it is believed that within 1,000-1,500 years the salinity of the sea became sufficient to support a large number of Mediterranean species. Today about 80% of Black Sea fauna are Mediterranean settlers.