South Holland was at the heart of an ancient supervolcano which sent ash into the atmosphere more than 400 million years ago.
A report released by the British Geological Survey (BGS) says new evidence suggests the origin of a huge volcanic ash layer is the supervolcano now beneath The Wash.
Geologists were previously unsure of the origin of an ash layer known as ‘Kinnekulle tephra’ which is found in the ground across Norway, Sweden, the Baltic region, Belarus and Poland.
“Scientists at the British Geological Survey and the University of Oslo have studied tiny crystals, smaller than the diameter of a human hair, extracted from boreholes in Lincolnshire and Norfolk.
“The analysis uncovered evidence of a 454 million-year-old supervolcano,” said a report from the BGS.
Tiny fragments found in both this area and in Scandanavia date from the same period and are believed to be from the eruption event.
“Ash from the eruption plume in what is now eastern England was blown across the Tornquist Sea which separated England and Scandinavia and settled on the sea floor.
“During the highly explosive ‘super-Plinian’-type eruption, hundreds of cubic kilometres of rock were launched into the stratosphere by the force of the blast,” the report adds.
Tim Pharaoh, principal author of the recently published paper, said: “More than 454 million years ago, a supervulcano now hidden beneath some of England’s flattest landscapes, produced some of the biggest eruptions in recorded Earth’s history. We believe that, thanks to cutting-edge analysis, we have been able to provide evidence that the source of the ash layer in Scandinavia originated from this supervolcano, reshpaing our understanding of England’s deep geological past.”
Scientists were able to examine zircon crystals which form within molten magma before a volcano erupts.
Over time, uranium within the zircon decays into lead isotpes which can be analysed to determine a precise age of the eruption.
One of the samples also contained younger zircon grains, dated to 453.70 millions years, reflecting a further eruption associated with the collapse of the volcanic caldera, says the report.
The samples had been taken decades ago, but only now has the technology been available to unlock their secrets.
Dr Pharaoh also said that, unlike faults, which can be reactivated, once a volcano is extinct, as in this case, that is it.
“Nobody needs to worry about the supervolcano erupting again,” he said.
