Deep below the seabed, 80 miles off the coast of Yorkshire, is a remarkable crater that has divided scientists – was it, thrillingly, created by an asteroid crash? Or more mundanely was it the result of geological salt movements?
Today, the decades-long scientific debate can be settled. The Silverpit crater 700 metres below the seabed under the North Sea was in all likelihood created by a direct hit from an asteroid or comet about the size of York Minster that hurtled towards the Earth more than 43m years ago.
The 160-metre-wide asteroid smashed into the sea causing a 100-metre-high tsunami, say scientists. It was probably a very bad day for any early mammals in the area – but not as bad as the consequences of the asteroid smash that wiped out the dinosaurs 66m years ago.
The Silverpit crater is nowhere near the scale of the Chicxulub crater in Mexico, when an asteroid about 6 to 9 miles wide struck Earth, resulting in a mass extinction of 75% of plant and animal species. But it is still interesting and, as the only impact crater near what is now the UK, extremely important, say experts.
Crater map
Uisdean Nicholson, a sedimentologist from Heriot-Watt University in Edinburgh who led the research team, said new seismic imaging had given them an unprecedented look at the crater.
Getting the proof was “definitely an exciting moment”, he said, describing the investigation as “a needle in the haystack approach”.
The 2-mile-wide crater, surrounded by a 12-mile wide zone of circular faults, was discovered in 2002 by petroleum geoscientists.
Those who found it believed it was indeed a hypervelocity impact crater, pointing to characteristics often associated with them including a central peak, circular shape and concentric faults.
It was initially estimated to be more than 60m years old and it made headlines. “Crater could be asteroid strike,” read a Guardian report from the time.
But some scientists were not convinced, arguing that it had a far less interesting origin story – it was most likely caused by the movement of salt rocks at depth.
The location of the Silverpit crater in the North Sea, showing the extent of the crater rim and the damage zone. Photograph: handout
“I feel like I’m spoiling the party,” said the geologist Prof John Underhill, from the University of Edinburgh, who led the doubters at the time. “It’s a less glamorous explanation, but that’s what the scientific data is saying.”
In 2009, there was a debate at the Geological Society that Nicholson remembers. “I was a PhD student at the time and it was quite a well-known debate, within geological circles at least.
“They had the big debate and then they had a vote. It was overwhelmingly decided that it was a non-impact origin. Most people favoured the mundane explanation and I think that reflects a tendency to reject the more spectacular explanation.”
The vote was 80-20 against the impact hypothesis, raising the question of whether geologists are naturally conservative. “There are different flavours of geologist,” said Nicholson. “People say I get too excited by certain ideas.”
Nicholson was asked to look at Silverpit because of his experience discovering another impact crater in west Africa.
With financing from the Natural Environment Research Council the Nicholson-led team used seismic imaging, microscopic analysis of rock cuttings and numerical models to provide what they say is the strongest evidence yet that Silverpit is one of Earth’s impact craters.
Asteroid crashes are mercifully rare, with none in recorded human history. The craters left by the impacts are also rare because “plate tectonics and erosion destroy almost all traces of most of these events”, Nicholson said. “Around 200 confirmed impact craters exist on land and only 33 have been identified beneath the ocean.”
Silverpit is exceptionally preserved and important, he said. “We can use these findings to understand how asteroid impacts shaped our planet throughout history, as well as predict what could happen should we have an asteroid collision in future.”
The findings are published in Nature Communications.