Using data from cores drilled in the seafloor as part of preparations for a rail tunnel that will link Africa and Europe, as well as seismic data, a team led by Daniel Garcia-Castellanos from the Institute of Earth Sciences Jaume Almera in Barcelona uncovered a 200-kilometre channel across the Strait of Gibraltar. The channel’s distinctive ‘U’ shape suggests that it was carved out in a torrential flood.

Around 5.3 million years ago, the Mediterranean was almost dry, but then it rapidly refilled.

By modelling the flow of water through the channel, the scientists were able to determine just how rapidly. They found that around 90 per cent of the water flowed in over a period of between a few months and two years, potentially causing the sea level to rise by as much as ten metres per day.

‘We do not envisage a waterfall, as is often represented: instead, the geophysical data suggest a huge ramp, several kilometres wide, descending from the Atlantic to the dry Mediterranean,’ said Garcia-Castellanos.

March 2010