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“Mediterranean Basin” is the name that is commonly assigned to that geographical area washed by this immense expanse of water, within which numerous civilizations were born, lived and disappeared, and where today about 450 million people live, belonging to the 22 countries sharing the same sea. A sea from whose waters entire islands have emerged, the scene of numerous legends. A sea which, however, could have been a salt lake: perhaps, even more, a desert.
In fact, thousands of years ago, an event known today as the Messinian salinity crisis occurred: the Mare Nostrum, so called by the Romans, dried up almost completely, leaving behind huge quantities of salt and very little water. What caused such a disastrous event? And what was the even more disastrous cataclysm that brought normality back to the Mediterranean?
From sea to desert: the evaporation of the Mediterranean
The Messinian is a period of more than 1.9 million years, the last part of the more extensive Miocene geological era. The name, as can be easily guessed, derives from the Peloritan capital, Messina. This period became famous precisely for the curious but unstoppable evaporation of the enormous expanse of water; to the eyes of the creatures who inhabited the Earth at that time would have appeared expanses of salt as far as the eye could see, deposited on the bottom and remaining there while the waters gradually dried up.
To understand the causes, it is necessary to take a step back and understand the true nature of the Mediterranean. It is, in fact, a marginal sea: that is to say, an expanse of water dependent on but separated from a larger sea by minimal factors, from ditches to ridges, remaining in contact with it in any case. The Mare Nostrum, in this case, is directly linked to the Atlantic Ocean via the Strait of Gibraltar.
And it is precisely from this small but very important channel that the evaporation of the Mediterranean began: in fact, it closed, interrupting the only connection with the ocean. Historians and scholars are still working to understand what were the real causes of this event.
The main theories, however, seem to be two: a movement of tectonic plates (the Arabian, Eurasian and African ones), or a drastic drop in the level of the oceans which, as explained by Fabio Florindo, director of the INGV Environmental Structure, it could be attributable to a glaciation.
Closed on all sides, the Mediterranean Sea became a real lake, very salty: within a few thousand years, it largely dried up, leaving behind it boundless valleys characterized by thick expanses of salt; numerous submerged islands, in that period, could have re-emerged; the water was reduced to a few “lakes” characterized by little depth, which can be compared today with the Great Salt Lake in Utah.
The cataclysm that filled the Mediterranean basin
The Mediterranean Sea, therefore, seemed destined to disappear forever. About 250,000 years after the closure of the Strait of Gibraltar, however, things changed: according to scholars, the Antarctic cap, responsible for the glaciation that had lowered the level of oceanic waters, withdrew, allowing it to rise again.
This factor created a real cataclysm: a flood of enormous dimensions, which allowed the ocean waters to pass the Strait of Gibraltar and go and fill the Mediterranean basin again. To get an idea of the power of water, just think how, according to scholars, it really took a few years to fill up again the sea that had taken thousands of years to dry out.
This happened because the power of the water gradually increased as the land beneath it eroded: 100 million cubic meters of water per second, an unimaginable quantity. Thus new depths were dug, those new emerged lands which went on forming were probably demolished.
The Mediterranean Sea, therefore, returned to being what we know today: even now, given the powerful salinity of its waters, it owes its constant exchange of water to the Strait of Gibraltar and therefore to the constant connection with the Atlantic Ocean, which allows it to remain stable and not evaporate again. However, such events could happen again in thousands of years: it will be up to the populations of the future to find solutions to ensure that the “Mediterranean desert” does not reform again.
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