A giant "super river" that carved its way through the chalky white hills connecting southern England to northern France about 450,000 years ago created the English Channel and made Britain into the island that it is today, scientists have discovered.
The prehistoric river flowed through the Strait of Dover withsuch erosive force that it churned out a channel deep enough to have kept Britain geographically isolated from the rest of mainland Europe since the end of the last ice age about 9000 years ago.
The scientists said they have found the sediments carried by the river, known as the Fleuve Manche, in the Bay of Biscay where seabed excavations have revealed the sequence of geological events that ultimately led to Britain becoming an island.
Professor Phil Gibbard of Cambridge University said the findings complete a jigsaw puzzle showing how the English Channel was formed when a huge glacial lake in what is now the North Sea broke through a natural dam that had held the lake back for thousands of years.
The huge volumes of water released created a mega-flood which flowed from the North Sea into the Bay of Biscay, gouging a channel deep enough to form a permanent natural barrier separating Britain from Europe when sea levels rose between ice ages, Gibbard said.
About 500,000 years ago, a land bridge of low hills connected southeast Britain to northern France.
The great rivers of northern Europe, such as the Rhine and the Thames, flowed into a freshwater, glacial lake in the southern end of the North Sea and this eventually led to overflowing across the land bridge, sending the water crashing into what was then a wide river valley which eventually became the English Channel.
