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On June 17, 2018, satellites captured images of the United Kingdom and Ireland.
Credit: NASA Earth Observatory
Some parts of Britain look much more like France than ever before.
In fact, Cornwall and South Devon on the British mainland are essentially part of France, at least geologically speaking. New research shows that these areas all come from an old piece of continental crust called Armorica. Previously, it was thought that the mainland of Britain consisted only of a piece of crust called Avolonia and a precursor segment of North America, Laurentia. The new study suggests it was more of a three-way merger.
To understand this process, 400 million years ago, well before the formation of the famous supercontinent Pangea, formed about 300 million years ago. It was the beginning of the Paleozoic, and most of the crust over the sea on Earth was divided into several continents, the largest being Gondwana, which contained the continental crust that would become the modern continents of the world. Southern hemisphere. The others were Avalonia (the forerunner of Canada and much of Europe), Laurentia (forerunner of North America), Barentsia, Baltica, Siberia and the north and south of China. [Photo Timeline: How the Earth Formed]
Old collisions
About 400 million years ago, Avalonia crashed into a piece of Laurentia. It was previously thought that this merger had created the ground that would then blend into Pangea, before ending up in the modern British continent.
However, a new study published Sept. 14 in the journal Nature Communications notes that another fragment is involved in this ancient dance: Armorica. Like Avalonia, Armorica was a fragment of crust that had ripped Gondwana and headed for Laurentia.
Today, land that was once Armorica is part of France and continental Europe.
Here's how the researchers think the British Isles were formed.
Credit: Plymouth University
"It has always been presumed that the border between Avalonia and Armorica was below what would appear to be the natural boundary of the Channel," said Arjan Dijkstra, professor of igneous petrology at the University of Plymouth. declaration.
But this is not the case, discover Dijkstra and his co-author Callum Hatch, now a preparatory geological specimen at the Natural History Museum in London. Instead, the line runs through Devon and Cornwall.
Ancient links
The researchers discovered this geological boundary by studying ancient magmas called lamprophyres and potassic lavas from 22 different sites in southwestern Great Britain. They examined atomic variations, or isotopes, of neodymium and strontium elements in rock samples.
Callum Hatch, of the Natural History Museum in London, inspects rock samples at one of the study sites called Knowle Hill Quarry.
Credit: Plymouth University
They found two very different variants of rocks north and south of an imaginary line across Devon and Cornwall. In particular, rocks south of the boundary were rich in radiogenic strontium and differed in their levels of neodymium isotopes relative to rocks north of the boundary. The southern rocks corresponded exactly to the lamprophyres of the same age found in Europe, on what was formerly Armorica.
The results could explain why southwestern Britain is rich in metals and tungsten, according to the researchers. Tin and tungsten are also common in Brittany in northwestern France, but not in the rest of Britain.
"We always knew that about 10,000 years ago, you could have walked from England to France," Dijkstra said in the statement. "But our results show that millions of years ago, the links between the two countries stronger."
Originally published on Live Science.
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