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Oceanography

The Mediterranean filled up in less than two years

The Mediterranean Sea nearly dried out six million years ago, when it got isolated from the oceans for a long period of time, due to actual tectonic lifting of the Gibraltar Strait. When the Atlantic once again found a way through the Straits, the Mediterranean filled with the biggest and most sudden flood that Earth has ever known. The finding is published in Nature.

Staff | 11 december 2009

Photo: Roger Pibernat

The Mediterranean basin, once a vast desert up to 1,500 feet deep, took between some months to two years to fill up, according to the researchers of the Consejo Superior de Investigaciones Científicas (CSIC). It was thought that this sea on land took 10 to 10,000 years to fill.

According to the article, the huge discharge of water, probably initiated by the tectonic subsidence of the Straits and the gap of the two seas, about 1,500 meters, was up to 1,000 times superior to the current Amazon River and filled the Mediterranean at a rate of up to 10 meters a day of rising sea level. The flood reconnected the Atlantic with the Mediterranean, causing, on the seabed, an erosion of about 200 kilometres long and several kilometres wide.

One of the responsible for the research, the CSIC researcher Daniel Garcia-Castellanos, who works at the Institute of Earth Sciences Jaume Almera (Barcelona), elaborates: "The flood that ended the desiccation of the Mediterranean was extremely short, and, rather than looking like a huge waterfall, it probably consisted in a more or less gradual decrease from the Atlantic to the centre of the Alboran Sea, a sort of 'mega rapid' through which water circulated at hundreds of kilometres per hour".
Tunnel between Spain and Africa

The researchers hope the article will help to plan the works of the tunnel to link Europe and Africa. When, some years ago, engineers studied the subsoil of the strait of Gibraltar, they encountered an unexpected problem: a groove of several hundred meters deep was filled by poorly consolidated sediments. Geologists and geophysicists thought at the time that this huge erosion had been caused by a large river flow during desiccation of the Mediterranean.

A very large and abrupt change in the landscape as the researchers have deduced could have had a significant impact on the climate of that period, something that has not yet been studied in sufficient detail, and which this study could help with. The technique also may serve to explore further flooding.

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