Rock samples collected in the English counties of Cornwall and Devon. Photo by University of Plymouth

Sept. 14 (UPI) -- Some 400 million years ago, landmasses collided to form the British Isles. Geologists have previously suggested the collision involved two landmasses, Avalonia and Laurentia.

But new research by geologists at the University of Plymouth suggests England, Wales and Scotland were formed by a collision among three landmasses. Armorica was also involved in the tectonic mashup.


Today, most of what's left of Armorica forms France's Breton peninsula. Analysis for rock formations in England's Devon and Cornwall counties revealed an ancient connection between England and France.

In the northern of Devon and Cornwall, rock properties recall those found in the rest of England and Wales. To the south, however, the rocks are closer in structure and composition to formations in France.

Rocks in southwest England boast elevated levels of tin and tungsten, similar to rocks found in Brittany and other parts of mainland Europe.

"This is a completely new way of thinking about how Britain was formed. It has always been presumed that the border of Avalonia and Armorica was beneath what would seem to be the natural boundary of the English Channel," Arjan Dijkstra, a lecturer in igneous petrology, said in a news release. "But our findings suggest that although there is no physical line on the surface, there is a clear geological boundary which separates Cornwall and south Devon from the rest of the United Kingdom."

Researchers used X-ray fluorescence spectroscopy to examine rock samples from 22 sites across Devon and Cornwall. Scientists also analyzed strontium and neodymium isotope ratios to better understand the history and evolution of the sample rocks.

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The analysis -- detailed this week in the journal Nature Communications -- revealed the petrologic relationship between Britain and France.

"We always knew that around 10,000 years ago you would have been able to walk from England to France," Dijkstra said. "But our findings show that millions of years before that, the bonds between the two countries would have been even stronger. It explains the immense mineral wealth of Southwest England, which had previously been something of a mystery, and provides a fascinating new insight into the geological history of the U.K."