July 18, 2007 — Britain is an island thanks to a megaflood that dug out the English Channel, according to a study released on Wednesday by the journal Nature.
The catastrophic flood, one of the mightiest in recorded history, occurred between 450,000 and 200,000 years ago and created a barrier to human migration to Britain that probably lasted for tens of thousands of years.
Imperial College London researchers Sanjeev Gupta and Jennifer Collier used high-resolution sonar to build up a highly detailed picture of the floor of the Channel.
They captured spectacular images of a vast submerged valley, dozens of miles wide and up to 165 feet deep, that was carved into the Channel's chalky bedrock.
They believe the valley is the flood-scoured remnant of a land bridge that was destroyed when a natural dam, running across what is now the Dover Straits, was breached.
This so-called Weald-Artois ridge was the southern wall of a gigantic lake which spanned what is now the southern North Sea.
