6 million years ago, the Mediterranean was completely separated from the Atlantic Ocean, when seismic movements raised the level of the Strait of Gibraltar. Dried out by evaporation, the fate of the Grand Blue seemed to be sealed. However, following a major seismic event, similar to that which had caused it to close off 700,000 years previously, the Atlantic managed to find its way across Gibraltar again, before spilling into the Mediterranean Sea. This was 5.33 million years ago.
A few years ago, a French/Spanish research team showed that at the time, the Mediterranean had filled up again in the space of only two years, while the Atlantic waters were making their way across Gibraltar, thanks to a seismic episode. According to their estimations, the level would have risen, at certain times and in certain places, by more than 10 meters per day, with an estimated flow of 100 million cubic meters per hour!
Working from geological and seismic data, these same researchers have revealed the existence of an ancient canal around 200 kilometers long, which crosses the Strait of Gibraltar from west to east, and which according to them was created via erosion due to the spilling of the Atlantic waters in the the dried “bowl” of the Mediterranean.
By using an incision model developed by hydrologists for mountain rivers, they managed to evaluate the duration of the flood. After a slow start which spread over several thousand years, the process suddenly accelerated dramatically: 90% of the volume of water coming from the Atlantic spilled in, during a very short period of time, somewhere between only a few months and two years. Their data suggests the existence of an immense flow of water descending down a slope several kilometers wide, from the Atlantic to the Mediterranean. Have a look at the video animation of the event: