Did a Catastrophic Flood Carve out the British Isles?

When people wanted to travel from Britain to France hundreds of thousands of years ago, all they had to do was walk. No ferry or tunnel required. And then 200,000 years ago, a catastrophic flood from an ice-dammed lake chopped off a bridge connecting Britain from the rest of mainland Europe.

This new theory about the formation of the British Isles is in this week's issue of the journal Nature, and was led by Dr. Sanjeev Gupta and Dr. Jenny Collier from Imperial College London.

The key discovery is a huge valley tens of kilometers wide and up to 50 meters deep carved into the sea floor of the English Channel. To the north of this channel basin there was a lake formed in the area now known as the southern North Sea. This lake was fed by the Rhine and Thames rivers. All this water couldn't escape out to the ocean because of glaciers and the Weald-Artois chalk ridge.

So it just piled up. And then some event, possibly an earthquake, caused the lake's rim to breach at the Dover Straight. Water poured out in a megaflood that discharged one million cubic meters of water per second, clearing away the land bridge, and scouring the sea floor.

The deluge lasted for months.

Gupta and his team used data from the UK Hydrographic Office to map the sea floor, looking for evidence to support this idea of a megaflood.
Once they'd found a hint to support this theory, they followed up with ships equipped with GPS and high-resolution acoustic measurement devices to map the sea floor with greater precision.

“The preservation of the landscape on the floor of the English Channel, which is now 30-50 m below sea-level, is far better than anyone would have expected. It opens the way to discover a host of processes that shaped the development of north-west Europe during the past million years or so,” said Dr Collier.

The researchers think there might have actually been two floods. The first occurred 425,000 years ago, and then a second flood followed 200,000 years later during the most recent ice age. This second flood was probably even more powerful than the first.

Next up, the researchers want to determined what impact this deluge had on human colonization of Britain, as well as the ocean currents in the
Atlantic Ocean.

Original Source: Nature