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I spent most of my life living in the east of England, so swimming in the sea meant swimming in the North Sea. This is fine if one is twelve years old or under, as they are famously immune to the cold and will happily turn bright blue, teeth chattering, before being persuaded to come from the icy deep and return to dry land. Even in August the North Sea requires a stout heart and nerves of steel to enter. So daily swimming in the warm, blue waters of the Mediterranean is utter, extraordinary
bliss.
The Med's only connection to the ocean is through the Straits of Gibraltar, to the Atlantic. As evaporation from the Sea greatly exceeds the inflow from rivers and the Atlantic into it, it is saltier than the Ocean. The cooler, less saline water from the Atlantic flows in through the Straits of Gibraltar and moves eastwards, as the climate is hotter in the Eastern Mediterranean and thus evaporation is greater. The water gets saltier and warmer as it heads east, eventually sinking as its density
increases, and flows back west as deeper water towards the Atlantic again.
The Sea was formed as the African tectonic plate moved north and into the European plate, essentially land-locking the Sea between the two continents. It has dried out almost completely a number of times. In the late Miocene period, 5.96 million years ago, tectonic movement closed the Straits of Gibraltar and most of the water in the Med evaporated, enough that African animals such as hippopotamus somehow found their way to Malta. Salt deposits show the Sea evaporated and refilled a number of times in the following years, until 5.33 million years ago when the Straits of Gibraltar reopened for the final time and the basin was flooded again in an event known as the Zanclean Flood.
Since the floor of the Mediterranean basin is essentially the bottom of where the ocean was, it would have been approximately 2.5 miles (4km) below sea level when it dried out. Temperatures decrease by about 10°C for every 1km you go upwards, due to decreased air pressure, and conversely downwards. So it has been estimated that the temperature at the bottom of the dried-out basin could have been 80°C.
The Zanclean Flood cascaded from the Atlantic Ocean into the basin at an unimaginable rate. In a period of between a few months and two years the entire Mediterranean Sea as we know it refilled in a deluge of Biblical proportions, 1000 times the flow of the Amazon, with a sea-level rise of 10m per day.
Tectonic plates are of course still active, the African plate still drives inexorably into Europe at a rate of about 10mm a year, the whole cycle of separation from the Atlantic and re-flooding will most likely happen again in the future, and eventually Africa will converge with Europe to obliterate the Mediterranean Sea altogether. Thankfully this will be over geological time, not my lifetime, so I'm safe to swim in the warm, blue waters for a while yet.
bliss.
The Med's only connection to the ocean is through the Straits of Gibraltar, to the Atlantic. As evaporation from the Sea greatly exceeds the inflow from rivers and the Atlantic into it, it is saltier than the Ocean. The cooler, less saline water from the Atlantic flows in through the Straits of Gibraltar and moves eastwards, as the climate is hotter in the Eastern Mediterranean and thus evaporation is greater. The water gets saltier and warmer as it heads east, eventually sinking as its density
increases, and flows back west as deeper water towards the Atlantic again.
The Sea was formed as the African tectonic plate moved north and into the European plate, essentially land-locking the Sea between the two continents. It has dried out almost completely a number of times. In the late Miocene period, 5.96 million years ago, tectonic movement closed the Straits of Gibraltar and most of the water in the Med evaporated, enough that African animals such as hippopotamus somehow found their way to Malta. Salt deposits show the Sea evaporated and refilled a number of times in the following years, until 5.33 million years ago when the Straits of Gibraltar reopened for the final time and the basin was flooded again in an event known as the Zanclean Flood.
Since the floor of the Mediterranean basin is essentially the bottom of where the ocean was, it would have been approximately 2.5 miles (4km) below sea level when it dried out. Temperatures decrease by about 10°C for every 1km you go upwards, due to decreased air pressure, and conversely downwards. So it has been estimated that the temperature at the bottom of the dried-out basin could have been 80°C.
The Zanclean Flood cascaded from the Atlantic Ocean into the basin at an unimaginable rate. In a period of between a few months and two years the entire Mediterranean Sea as we know it refilled in a deluge of Biblical proportions, 1000 times the flow of the Amazon, with a sea-level rise of 10m per day.
Tectonic plates are of course still active, the African plate still drives inexorably into Europe at a rate of about 10mm a year, the whole cycle of separation from the Atlantic and re-flooding will most likely happen again in the future, and eventually Africa will converge with Europe to obliterate the Mediterranean Sea altogether. Thankfully this will be over geological time, not my lifetime, so I'm safe to swim in the warm, blue waters for a while yet.