Scientists solve ancient Mediterranean flood mystery

The team, led by Daniel Garcia-Castellanos from the Research Council of Spain (CSIC), found that the catastrophic Zanclean flood occurred when Atlantic waters found their way into the cut-off and desiccated Mediterranean basin.

The researchers said that a 200km channel across the Gibraltar strait was carved out by the floodwaters and the resulting flood could have filled the basin within two years, journal Nature reported.

Garcia-Castellanos explained that he and his colleagues laid the foundations for this study by working on tectonic lakes. They developed a model of how the mountain lakes quickly "cease to exist" when erosion produces "outlet rivers" that drain them.

This same principle, he said, could be used to explain the Zanclean flood that reconnected the Mediterranean with the rest of the World's oceans. "We could for the first time link the amount of water crossing the channel with the amount of erosion causing it to grow over time," he told BBC.

Using existing borehole and seismic data, his team showed how the flood would have begun with water spilling over a sill. The water would have gradually eroded a channel into the strait, eventually triggering a catastrophic flood, Dr Garcia-Castellanos said.

He and his colleagues created a computer model to estimate the duration of the flood, and found that, when the "incision channel" reached a critical depth, the water flow sped up. In a period ranging from a few months to two years, the scientists say that 90 per cent of the water was transferred into the basin.

"This extremely abrupt flood may have involved peak rates of sea level rise in the Mediterranean of more than 10m per day," they said. Previous estimates of the duration of the flood were very variable, said Dr Garcia-Castellanos, because scientists "had to assume the size of the channel" rather than measure it. Some estimates suggested that the flood continued for as long as 10,000 years.

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