The ancient landscape, which is now covered by 1,000 metres of water and 2,000 metres of sediment, was found during a six-month survey of about 10,000 square kilometres of seabed – conducted by bouncing sound waves off it.

‘It’s supposed to be just boring layers of mud and sand down there,’ Nicky White of the University of Cambridge told the BBC. ‘What we found was a big surprise: three-dimensional surfaces of hills and valleys.’ When the results of the survey were plotted out, they showed clear evidence of a river system draining down towards what looked like a coastline. Pollen fossils in the rock – obtained from drill samples – confirmed that it was once land.

‘This hidden landscape was above the waves between about 56 million and 55 million years ago,’ said White. ‘It must have risen about a kilometre within
two million years and then subsided just as quickly. That is extraordinary.’

The researchers suggest that a sudden pulse within a plume of hot rock rising within the mantle may have been responsible for the rapid rise of the landmass. 

September 2011