Britain Became Separated from Mainland Europe After A Catastrophic Flood
18 Jul, 2007 07:00 pm
Sanjeev Gupta, geologist, explains his findings published today in Nature on glaciers role in forming the English Channel.
We have been mapping the floor of the English Channel using sonar data. Imagine taking the sea away and being able to see its landscape. We have discovered a really large valley in the center of the English Channel. We can resolve the features in that valley at very high resolution that tell us that the valley was carved by a very huge catastrophic flow of water, which links well with an old level. The idea is that a catastrophic flood breeched a rock ridge at the Straits of Dover and separated Britain and France. It was actually an old idea, but there was never any direct evidence. So we have provided the first evidence that shows this.
How did you reach those conclusions?
We see very distinct landforms in the landscape in this valley. In addition, by comparison with other areas in the world, in particular an area in the Western US where there is a huge catastrophic flood 15,000 years ago carved an extraordinary landscape in Washington State. It is called the Channeled Scabland, the landforms there are analogous. They are the same as the features that we see under the sea under the the English Channel. The idea is that at the peak of the glaciations when the ice sheets extended from Europe right across into Britain across the North Sea a huge lake built up in the Southern North Sea bounded to the North by ice sheets and to the South where the Dover Straits are at the moment there is a big rock ridge made out of chalk, which extends from England into Northern France. This formed a dam of lake water, and this water built up and eventually breeched this rock dam. After which there was a huge outflow of water into the English Channel, which carved a whole system of valleys.
What are the implications?
There are some pretty major implications. This event caused a wholesale reorganization of European rivers. For example, when sea levels were much lower when the North Sea was land and the English Channel was land, the Rhine and the Thames used to flow to the North into the Norwegian Sea. This event caused it to divert through the Straits of Dover and through the Channel. The other major implication is that once this gap was created at the Straits of Dover and sea levels rose, the North Sea joined the English Channel, and thus separated Britain. That is how Britain became an island.
Interview by: Christopher Le Coq
Sanjeev Gupta is a geologist at the Imperial College London in the UK