A little over 5 million years ago, water from the Atlantic Ocean found a way through the present-day Strait of Gibraltar. According to this theory, oceanic water rushed faster than a speeding car down a kilometre-high slope towards the empty Mediterranean Sea, excavating a skyscraper-deep trough on its way.
The Med was, at the time, a largely dry and salty basin, but so much water poured in that it filled up in just a couple of years – maybe even just a few months. At its peak, the flood discharged about 1,000 times the water of the modern-day Amazon river.
