Showing the AHOB chart of glacial and interglacial periods, he explained post-glacial sea rises, but said that 450,000 years ago most of Britain was accessible to migration from Europe. The only block was the river system (Thames, Rhine, Seine) all going to the Atlantic. Migrants probably did not come from Brittany, but via Germany and Belgium.
A domed chalk ridge linked England to France, of which Dover cliffs were part, with the same chalk escarpment left on both sides of the Channel.
Some of what followed of current thinking remains speculation/guesswork, he suggested we come back in a couple of years to test it. Mesolithic Britain separated from France 6200BC, but was separated before. Research in 2007 using new technology followed the palaeo-Arun offshore extension, and discovered a sudden drop-off into a cut valley running down the channel, and similar results occurred from the Solent. Elongated islands and funnel shape resulted from strong tides, with very little silt – carved out by a lot of water very quickly. In the northern Channel a series of islands with elongated flat tops pointed at the end were found – classic catastrophic flood terrains.
As the ice melted a lake formed where the North Sea now is, developing behind the chalk ridge. The first Brexit was 450,000 years ago as the chalk ridge started to overflow. Dover being prone to earthquakes, the dam was breached, and the water began to gouge channels. These rifts would have silted up repeatedly. There were two major breaks, 450,000 and 150,000 years ago, when a million cubic metres of water per second for several months would have poured through. At the end of the last glacial, rising sea levels meant a final break, after glaciers scooped the bed of the ice sheet.
A maximum of 28,000 years ago the ice slowly retreated releasing waters. Doggerland provided an access area to Britain, but by 6500BC was a low lying area of marsh and small islands linked to Europe. It had a good climate (warmer than today) and good land. An undersea landslide in Norway (the Storegga slide) created one of the greatest tsunamis the world has ever known. It could have been caused by unstable land, and earthquake, or an explosion of methane hydrate.
All Doggerland was submerged, and England was an island. Funnelled from the North Sea, the water broke through the last remnants of the Channel chalk ridge. The impact would have been catastrophic.
Goodbye to Europe – again!