Buzz
The White Cliffs of Dover mark the closest point between England and France, while the Dover Strait once served as a land bridge linking the two regions. Photo by Ben Pruchnie/Getty Images.In 2016, British voters narrowly approved the decision for Britain to exit the European Union, a move officially announced by Prime Minister Theresa May. However, Brexit isn’t the first instance of England breaking away from the continent.
Around 450,000 years ago, during the ice age, sea levels were so low that crossing from France to the UK didn’t require a ferry or the Channel Tunnel. Instead, the English Channel was a dry expanse of land, resembling a frozen tundra with a few small rivers.
An artist's depiction shows the cascades and lakes that played a role in forming the Strait of Dover in the English Channel. The scene portrays modern-day France in the foreground, with Dover, England, in the background. Image credit: Chase Stone/Imperial College London.Scientists have long believed that the channel formed when a proglacial lake, located in front of an ice sheet in the North Sea, overflowed. However, a recent study published in Nature details the two-stage process that led to the historic separation of Britain and Europe, as explored by researchers from Imperial College London, Belgium, and France.
According to a press release from Imperial College London, the first clues about the channel's formation appeared in the 1960s, when engineers conducting surveys for the Channel Tunnel uncovered large holes in the Dover Strait's sea floor. In the 1980s, the late marine geologist Alec Kenyon-Smith of Bedford College proposed that these holes may have been carved by ancient waterfalls, created when a lake spilled over a chalk rock ridge that once contained it.
A bathymetry map of the Dover Strait reveals a deep valley carved through the center of the strait. The chalk rock ridges in southern Britain and northern France would have once been connected before the strait was breached. Image credit: Imperial College London.Scientists are still unsure about the exact cause of the lake's overflow. One possibility is that a chunk of the ice sheet broke off and plunged into the lake, triggering a surge of water over the ridge. Another theory is that an earthquake might have caused the ridge to collapse.
However, that initial flood was only the beginning. A subsequent release of water from smaller lakes in the ice sheets of the North Sea may have caused a second flood, which further eroded the channel.
"The breaching of the land bridge between Dover and Calais stands as one of the most significant events in British history, having a lasting impact on the identity of our island nation to this day," said Sanjeev Gupta, an Imperial College Earth science and engineering professor and co-author of the study, in a press release. "When the Ice Age ended and sea levels rose, permanently flooding the valley floor, Britain became physically disconnected from the mainland. Without this dramatic breach, Britain would still be part of Europe. This is Brexit 1.0 — the Brexit no one voted for."
The researchers still don't have a clear timeline for when the floods that created the English Channel took place. To determine this, they'll need to extract core samples from the sediment in the holes at the bottom of the channel.
