Around six million years ago, something rather drastic happened: the world lost an ocean. Fortunately, it’s returned since then, but during the Messinian Salinity Crisis, there was no Mediterranean Sea. Instead, there was a bit of a wading pool… or possibly even completely dry land.
During the Messinian period of the Miocene epoch, it seems that what is now known as the Strait of Gibraltar actually closed up, disallowing the flow of water from the Atlantic and resulting in the Mediterranean seabed simply evaporating – in some places up to 3 miles below sea level. As this occurred, there were also some cases of extreme erosion, creating several enormous canyons in and around the coastline, after which the evaporation procedure left behind deposits of evaporite mineral sediments.
It was during some routine geological work in the Mediterranean that geologists found evidence for this ancient desiccation of the sea, as they found mineral deposits that only form when large amounts of isolated salt water evaporate over time. Combined with layers of marine fossils, which indicats repeated periods of drying and flooding, as well as now submerged canyons that are cut into the sides of the sea basin, geologists realized there was enough evidence to confidently assert that, for some period of time, there was no Mediterranean sea.
During the period of dehydration, earth’s sea levels rose by 10 meters – if this happened today, many of the world’s major cities and landforms would be completely submerged! The global climate was also changed during this time, causing almost the entire Mediterranean basin to become a wasteland devoid of plant and animal life, and at 3 meters below sea level inside the basin, the temperature would have been almost 50 degrees hotter at the bottom than the temperature at sea level. With that kind of heat in and around the basin, added to the increased salinity of the area, the great civilizations of Egypt, Greece, Rome, and any other known Mediterranean culture could not have developed – unless the sea was refilled.
Eventually, the Strait of Gibraltar opened again, allowing water from the Atlantic to once again refill the Mediterranean basin, but not until the earth’s oceans had already been permanently altered by the loss – the freezing point of the ocean had been raised, and the average salinity of seawater significantly reduced. Even today, the salinity of the Mediterranean is higher than the North Atlantic, and thus it continues to have a higher rate of evaporation.
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Tomorrow: Iranian Salt Men.