Buried deep in the east coast of England, scientists have discovered an enormous ancient volcano several times more powerful than Mount Etna (pictured above).
The volcano, which lies under the counties of Norfolk and Lincolnshire, erupted with the force of several thousand hydrogen bombs 454.4 million years ago, blowing ash all the way to Scandinavia.
Researchers believe it is responsible for forming the ‘Kinnekulle tephra’ – an enormous bed of volcanic ash still found today across Norway, Sweden, the Baltic region, Belarus and Poland.
This remarkable discovery is “reshaping our understanding of England’s deep geological past”, said Dr Tim Pharaoh, a geophysicist at the British Geological Survey and lead author of the study.
The clues that this previously hidden volcano existed lay in rock samples taken from two boreholes spaced 65km (40.4mi) apart in Norfolk and Lincolnshire.
But the ancient volcano may have spanned an area far bigger than 65km.
“This was probably not a simple, cone-shaped volcano,” said Dr Dan Condon, a research scientist at the British Geological Survey who co-authored the study.
He told BBC Science Focus that the evidence points to a large and complex volcanic system containing several cauldron-like hollows – known as ‘calderas’ – extending across tens of kilometres above an extensive body of magma.
The researchers analysed tiny particles embedded in the ancient volcanic rock – known as zircon crystals – which enabled them to calculate the volcano’s age “at the highest levels of precision currently achievable”.
“Zircon crystals act as tiny natural clocks,” explained Condon. When zircon crystallises from magma, it incorporates uranium into its structure, which over time changes into lead.
By measuring the rate of this change, Condon and his team discovered that the rock in the ancient English volcano and the Kinnekulle tephra in northern Europe formed at the same time.
As well as calculating their age, they analysed the composition of the rock samples and found that their ‘chemical fingerprints’ also matched.
“Trying to estimate the size of eruptions we have not witnessed is like trying to guess the picture on a jigsaw puzzle with only a few bits in place,” said Prof Jenni Barclay, a volcanologist at the University of Bristol who was not involved in the study.
This study finds striking similarities in the age and composition of rocks located hundreds of miles apart, making us, according to Barclay, “more certain these pieces are from the same eruption”.
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