Geologists have discovered a vast new landscape that rose above the north Atlantic waves 56 million years ago.
It was caused by a sudden up-welling from the Earth’s mantle and may explain rapid climate change that took place at about that time.
Discovered by UK researchers, the river-valley system is off the north west of Scotland, about 200km west of the Shetland Islands.
The results are published in the journal Nature Geoscience.
Over a six-month period the researchers reflected sound waves off the seabed to discover the new landscape.
They surveyed about 10,000 sq km of seabed; the sound waves reaching depths of up to several kilometres.
“It is supposed to be just boring layers of mud and sand down there,” said Nicky White from the University of Cambridge, UK who was involved in the project.
“What we found was a big surprise: three-dimensional surfaces of hills and valleys,” he told BBC News.
The lead author Ross Hartley, from the University of Cambridge, UK, plotted out the surfaces and discovered clear evidence of the drainage pattern of a river system, going down to what looked like a coastline.
It looked just like the surface of land, except that it was under a thousand metres of ocean, and a further 2000m of accumulated sediment.