Current textbooks teach that Britain — once a peninsula of continental Europe — split from the great land mass after a long process of erosion and rising sea levels over millions of years. Geological scientists now say that the hills that once joined Britain to France were swept away by a biblical-style flood that turned the peninsula into an island in 24 hours.

Long has it been thought that the English Channel had formed by slow erosion combined with rises in sea level that took place over millions of years. Now geological scientists say that the hills that once joined Britain to France, in fact, were swept away by a “biblical-style flood,” causing the peninsula of continental Europe to split and become an island — in 24 hours.

The catastrophic flood, which would have taken place between 400,000 and 200,000 years ago, instantly turned Britain into a separate land mass, changing forever the way it would develop, new data proposes.

A recent advanced sonar probe, led by Dr. Sanjeev Gupta of the Department of Earth Science and Engineering at Imperial College, London, could rewrite British prehistory, as current textbooks teach that Britain — once a peninsula of continental Europe — split from the great land mass after a long process of erosion and rising sea levels.

“This could have been one of the most powerful flood events ever known on Earth,” Professor Chris Stringer, head of human origins at the National History Museum in London, told London’s The Times.

Scientists at London’s Imperial College developed the sonar technique — known as bathymetry — a few years ago. The technology uses satellite positioning equipment, computers and software, to allow the creation of a three-dimensional image of the landscape beneath the boat.

When Gupta used the advanced sonar technology to survey the English Channel’s sea floor several miles off the coast of Sussex, he and his team were surprised to find the remains of a huge valley, running southwest from the Strait of Dover. The geological team further discovered deep bowls, scour marks and piles of rubble on the sea bed that could have only been created by a giant torrent of water, according to the writers of the new survey report.

“In places, this valley is more than seven miles wide and 170 ft. deep, with vertical sides,” said Gupta in an abstract published at an academic conference. “This suggests the valley was created by catastrophic flood flows following the breaching of the Dover Strait and the sudden release of water from a giant lake to the north.”

Today the English Channel is 520km long, 30-160km wide, about 30-100m in depth and slopes to the southwest.

Specifically, Gupta proposes that Britain and France were “linked by a high ridge of chalk hills, running roughly between Dover and Calais.” Northeast of this ridge the land sloped down until it met the North Sea. During one of Europe’s glaciations, an ice cap up to a mile thick reached so far south that it stretched from Scotland to Denmark, effectively damming the North Sea. This turned into a freshwater lake, which, fed by rivers, deepened over thousands of years.

Between 400,000 and 200,000 years ago, the lake, “hundreds of feet above sea level,” breached the chalk ridge and made good its escape toward the Atlantic. The water washed away the soft chalk hills and left the British Isle a separate land mass — all in the span of 24 hours.

“One day it just overflowed the top of the chalk ridge and started pouring over,” Stringer told The Times. “Once the torrent started, it would have ripped through the soft chalk and poured down towards the Atlantic.”

Changes in climate were accompanied by changing sea levels. At the height of an ice age, these would have been low. During interglacial periods, when the climate was warm, sea levels rose. But even when water was locked up in the ice sheets and sea levels plummeted, the Rhine and the Thames rivers dumped meltwater into a major river system that flowed along the floor of the Channel.

This means that once the Channel formed, the land crossing from northern France to Britain was gone.

Interestingly, a group of French researchers, working separately from Gupta, has traced the course of this catastrophic flood, finding a giant submerged river valley running southwest along the seabed between Normandy and Cornwall.

This theory, outlined in Stringer’s new book “Homo Britannicus: The Incredible Story of Human Life in Britain,” may help solve one of the enduring mysteries of British archaeology: the apparent abandonment of the British Isles by humans for 120,000 years.

Researchers such as Stringer have found that early humans first arrived in Britain at least 700,000 years ago. They were driven out by repeated glaciations but kept on returning whenever the land warmed up. Yet between 180,000 and 60,000 years ago, they vanished completely. During that time, Britain had periods of Mediterranean warmth when wildlife flourished. Although early humans would have thrived, there are no signs of them.

Nick Ashton, a senior curator at the British Museum, said the flood and resulting river valley could be the explanation.

Not only is the discovery significant, but the advanced sonar technology, too, has significant implications.

“Most of the world’s seabed is still a mystery to mankind,” Dr. David Miles, chief archaeologist of English Heritage, told The Observer a few years ago in a special report on the same advanced sonar technology “We have better images of Mars and Venus than of two-thirds of our own planet. Now we can put that right.”

Given that Britain is a maritime nation, for which the sea has been an immense influence, finding out the secrets around its shores seems particularly important.

Resources

The flood that made Britain
by Jonathan Leake
The Sunday Times, Sept. 24, 2006

Flood made Britain into an island ‘in 24 hours’
by Tim Hall
The Telegraph, Sept. 25, 2006

Britain became island in 24 hours
by Lester Haines
The Register, Sept. 26, 2006

Additional

Britain’s drowned landscapes
by Robin McKie
The Observer, Sept. 21, 2003

Hi-tech could reveal ‘drowned city’
BBC News, Sept. 23, 2003