Tsunami 'turned Britain into an island overnight'

Britain could have been turned into an island almost overnight when an underwater landslide off Norway 8,000 years ago triggered a tsunami with waves more than 30ft high, a geologist said yesterday.

The waves may have breached the bridge between England and the Continent when they swept over Scotland, scattering settlements of hunter-gatherers, Professor David Smith, of Coventry University, told the British Association for the Advancement of Science conference in Glasgow.

Although sea levels were already encroaching on the bridge, the tsunami may have hastened the process, he said. A 25cm-wide band of sediment found in the cliffs of east and north Scotland and in Norway that was dumped about 7,800 years ago coincided with a landslide on the sea floor in Storegga, Norway, Prof Smith said.

Sediments swept into the sea over thousands of years by glaciers would have slipped, covering an area of the sea floor as big as Scotland. The landslide sent ripples across the North Sea that hit Britain, Norway and Denmark. Britain, connected to Holland and Denmark by a low-lying bridge of land, would have been cut off temporarily by the waves.

Prof Smith said: "It was about the same time Britain was beginning to be isolated from the mainland. Obviously it may have hastened the separation from the mainland."