Brexit the first: our violent geographical divorce from France

The people may have (narrowly) chosen to leave Europe, but Britain itself broke away from the continent long before that.

In a new study, researchers have demonstrated how the island of mainland Britain arose through a two-stage flooding process, severing its link with France.

This process took millennia, beginning around 450,000 years ago, and finishing around 120,000 years ago. The study was a collaborative effort between geoscientists in the UK, France, and Belgium.

Researchers re-analysed old data and previously held theories, but combined this with new high resolution mapping of the sea floor to determine the geological history of the Channel.

The physical connection between Britain and France was a 32km rock ridge, comprised of mostly chalk. This ridge separated an iceberg-filled lake from the North Sea, which was also likely covered in ice.

The land that became the Strait of Dover would have resembled Siberian tundra, with a cold, forbidding landscape and little vegetation.

Due to changing water levels through glacial melting, the lake overflowed and huge waterfalls swept over the ridge. This eroded deep holes into the chalk, weakening the integrity of the land bridge.

The size of these holes are staggering – up to 140m deep and 4km wide, resulting purely by the lake overflow forming plunge pools.

Although this erosion partially broke the ‘dam’ between the lake and the sea, Britain and France remained connected for thousands more years.

The second stage, which shattered the tether between the two landmasses, was a catastrophic megaflood about 160,000 years ago.

The geological map data reveals a massive chunk carved into the Channel, overlaying the previous holes.

This was likely due to further glacial melting in other lakes upstream which filtered down and built up into this megaflood.

The weakened ridge could not hold up to the flooding, and finally broke, splitting Britain from its mainland connection. Further erosion and rising sea levels shaped Britain into the island it is today.

This study is exciting not only for evidence of how Britain left the mainland, but also for understanding the early colonisation of the land.

An island is more difficult to migrate to than a bridged peninsula, and early populations living on Britain lost their land route back to the mainland.

Through the action of erosion, combined with spectacularly cataclysmic flooding, the physical link between Britain and mainland Europe was broken apart forever.

As the author of the paper, Sanjeev Gupta, remarks, “You could say it was a violent beginning to Brexit 1.0”. Let’s hope the political Brexit of the present is less dramatic.

Image: Max Pixel

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