Between 5 and 6 million years ago the Mediterranean Sea almost completely dried up. The cause was the tectonic movements that closed the Strait of Gibraltar connecting Europe and Africa.
Deprived of the influx of water from the Atlantic, the Mediterranean could not balance that loss with the drainage of the rivers, surpassed by evaporation. Large deposits of salt began to form on the ancient seafloor. Some of these deposits are still visible in the Sicilian city of Messina, after being uplifted by the action of tectonic plates.
At the same time that the water level dropped, the rivers that poured into the Mediterranean began to form gorges similar to the Grand Canyon of the Colorado, more than 1,000 meters deep, while the coast and the bottom, free from the heavy load of the water, they underwent an isostatic lift of hundreds of meters. It is estimated that this occurred 5.96 million years ago.
But some 630,000 years later the water from the Atlantic managed to break the land barrier of the Strait of Gibraltar and the waters re-entered filling the Mediterranean. It is estimated that the level could rise up to 10 meters a day, which was catastrophic for the life, flora and fauna established there. Obviously, no modern human (homo sapiens ) was there to suffer the consequences, since our species would appear more than five million years after that.
But there is another similar event that homo sapiens if he witnessed:the flooding of the Black Sea. It is just one of the many hypotheses that are considered to explain the formation of this sea, but incidentally it provides a source of origin for the subsequent myths of the universal deluge that we find in the Gilgamesh poem and in the Bible.
According to this theory, the Bosphorus Strait would have closed just as the Gibraltar Strait did, drying out large tracts of land to the north and west of the current sea. For thousands of years, fresh water from the Black Sea would have flowed into the Mediterranean, until around 5600 B.C. perhaps a global sea level rise caused the Bosphorus to rupture.
Suddenly, the salty water of the Mediterranean began to cascade through the Bosphorus, with a force 400 times more powerful than that of Niagara Falls and pouring 42 cubic kilometers of liquid a day. The water level would have risen about 10 centimeters per hour, flooding more than a kilometer of coastline per day, until after a few weeks more than 150,000 square kilometers of land were buried under water.
As we said, at that time the flooded areas would be inhabited by Neolithic settlements. Entire towns that were taken by surprise by the rise in water level and that, day after day, would try to escape inland, moving families, cattle and belongings, with more or less luck.
An expedition led by researcher Robert Ballard in 1999 found evidence of occupation and human-built structures, as well as freshwater molluscs at the bottom of the Black Sea. This would be indicative of the previous existence of a freshwater lake, and of the subsequent marine flooding.
The survivors of that catastrophe and their descendants would have transmitted the story orally for generations, until it finally gave rise to the myths of the universal deluge.
According to scientists, in the distant future (within another 5 million years) the Strait of Gibraltar will close again and the Mediterranean will dry up again, being reduced to a few hypersaline lakes. The Black Sea will suffer the same fate, and the process will begin again.
However, other scholars believe that such an event never occurred, and that in fact the water from the Black Sea has always flowed, and continues to flow, towards the Mediterranean.