A Megaflood Made England an Island

England became an island as a result of a massive flood that tore through a land bridges to France 400,000 years ago, a study of  high-resolution sonar images of the bottom of the English Channel shows. The torrent of water and boulders carved the cliffs of Dover, and left deep scars on the channel bed, researchers report in the journal Nature.

The megaflood, they hypothesize, was caused by a vast freshwater lake, covering what is now the southern North Sea, breaking through a natural chalk dam at what is now the Dover strait. "This prehistoric event rewrites the history of how the UK became an island," said one researcher. (More England stories.)