The period when the Mediterranean dried up into a salty desert

Tectonic plate movements and falling sea levels once separated the Mediterranean Sea from the Atlantic Ocean, causing seawater to evaporate and form a vast saline basin.

The Mediterranean Sea transformed into a giant saline basin about half a million years ago . Evidence of this geological disturbance still exists today, and there is a possibility that a similar disaster could happen again in the future, according to IFL Science . This event is called the Messinian salinity crisis. According to the hypothesis of researchers, changes in sea level prevented the Atlantic Ocean from flowing into the Mediterranean Sea, causing the sea to dry up almost completely 5.33 - 5.97 million years ago.

Simulation of the Mediterranean during the Messinian salinity crisis. (Photo: Paubahi).

Many scientists believe that the Messinian salinity crisis occurred due to the discovery of a 1.5-kilometer-thick layer of salt along the Mediterranean seafloor, first confirmed in the early 1970s. However, not all scholars agree on the nature or scale of the event.

One of the main causes of the Messinian salinity crisis was likely plate tectonics . The African and Eurasian plates slowly crashed into each other over thousands of years. Eventually, their slow-motion collision led to the closing of the Strait of Gibraltar, a narrow body of water connecting the Atlantic Ocean and the Mediterranean Sea.

Another factor is that falling sea levels make it harder for ocean water to flow through the Strait of Gibraltar. A 2015 study linked the drop in global sea levels around this time to the expansion of the Antarctic ice shelf, which traps more of the world's water around the South Pole and away from the North Atlantic.

The Mediterranean is particularly vulnerable to these changes. Because it is located in a relatively warm and dry part of the planet, seawater evaporates at a rapid rate. Without the replenishment of water from the Atlantic, the enclosed sea dried up within a few thousand years, leaving behind a salt-filled basin that connected part of North Africa to southern Europe.

It was then theoretically possible to travel from present-day Morocco to Spain or from Libya to Italy. In fact, some animals did. Several Spanish islands, such as Mallorca, Menorca, Ibiza, and Formentera, were invaded by land-dwelling animals during this dry period. At the same time, the crisis devastated the Mediterranean's marine biodiversity, killing 89 percent of its endemic marine species.

After a long separation, tectonic activity caused the Strait of Gibraltar to open again, allowing a huge amount of Atlantic water to rush into the Mediterranean Sea. Known as the Zanclean flood, it was one of the most intense floods ever to occur on Earth.

Even today, the Mediterranean Sea remains saltier than the rest of the Atlantic Ocean, partly due to the same geographic and climatic conditions that contributed to the Messinian salinity crisis. Although no longer separate from the Atlantic Ocean, the Mediterranean still has limited water exchange through the Strait of Gibraltar and high evaporation, leading to increased salinity.

It is possible that a similar event will occur again in the future. The Earth's tectonic plates are constantly shifting, and the Mediterranean region is particularly complex, showing many irregular fault zones and tectonic debris piled up on top of each other. If the African plate continues to move towards the Eurasian plate, the two plates could merge to form the Afro-Eurasian supercontinent, wiping the Mediterranean off the map.