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Evidence of a gigantic impact crater off the Scottish coast



Reddish colored rocks of the Stac Fada deposit.
Image: University of Oxford

About 1.2 billion years ago, a one-kilometer-wide asteroid hit northwestern Scotland. The problem is that the scientists do not know exactly where the meteorite hit, as the traces of the crater are long gone. However, with new research, scientists are beginning to investigate the impact zone.

A study by Kenneth Amor from the Institute of Earth Sciences at Oxford University suggests that an asteroid measures between 1 and 2 kilometers. About 1.2 billion years ago, Scotland's Minch Basin was completely destroyed. The cherished location of this ancient collision lies just off the coast of the Highlands, about 15 to 20 kilometers west of Enard Bay.

The crater is no longer visible on the seabed since it has been buried by younger rocks over hundreds of millions of years. Evidence of the ancient impact was found in the reddish-colored rocks of the Stac-Fada deposit on the nearby shores. The analysis of these minerals allowed Amor and his colleagues to triangulate the location of the crater, which they described in a study published today in the Journal of the Geological Society.

The red circle marks the planned location of the 1.2 billion year old impact crater.
Image: Google Maps / Gizmodo

"This is another interesting chapter in the search for the crater," said Gordon Osinski, a geologist at Western University in London, Ontario, Canada, who is not involved in the new study Gizmodo in an email with. "If the authors are correct, this would be the first confirmed crater in the UK."

The data presented in the new publication suggests that the feature lies somewhere between the Scottish mainland and the Western Isles, but a geophysical survey is needed to provide final proof. Amor and his colleagues estimated the size of the crater to be about 13 to 14 kilometers (8 to 8.7 miles) wide and 3 kilometers (1.9 miles) deep.

"It is gratifying to know now that Britain is blessed with its own impact crater. Jay Melosh, Professor of Earth, Atmospheric and Planetary Sciences at Purdue University, wrote an e-mail to Gizmodo. "Unfortunately, the crater itself is unlikely to become a tourist attraction like the Arizona Meteor Crater in the US, as it is completely buried under thick layers of younger rocks," said Melosh, who also was not involved in the new study.

Inklings of this ancient collision first appeared in 2008, when Amor, along with researchers from Aberdeen University, found evidence of the apparent debris field of an ancient asteroid impact. However, the exact position of the crater could not be determined.

In 2015, a gravitational analysis of the region revealed that the crater was about 50 kilometers wide and was located east of the Stac Fada outcrop. A narrow belt that runs about 50 km north and south along the northwest coast of Scotland.

"However, this new study confirms this estimate and, based on the flow patterns in the deposit, suggests that the crater is only about 12 km long and lies to the west of the outcrop! "Melosh wrote. "This uncertainty illustrates the difficulty of reconstructing the entire crater from a narrow strip of its ejected material. But it also shows the importance of careful analysis of flow directions based on subtle evidence in the deposit.

The crater may be invisible, but the associated rocks on the shore provided important clues to the cataclysmic event. The approximate position of the crater was determined by a few indirect methods.

"During the impact of the asteroid, tons of powdered and molten rock, mixed with hot gases, were ejected at high speed in all directions from the rapidly forming crater," Amor said in an email to Gizmodo. "These debris flows [traveled] Over long distances at a speed of several hundred kilometers per hour, and finally they came to a standstill, especially when they hit an obstacle like a hill, and we saw evidence that the debris flow came to a standstill, but the material behind it Still trying to move forward and being pushed over the jammed material, this provided really good directional information for the origin of the crater. "

Amor and his colleagues also studied the orientation of magnetic particles in rocks.

" The mixture of hot gas and powdered rock similar to a high-density fluid, "said Amor. "The orientation of the mineral grains can provide directions to the current direction. This technique has been successfully used to determine the current direction in old river systems and volcanic ash deposits, but this is the first time it has been used for a meteor impact. "

This particular impact occurred when life was still very much alive primal stage. No plants or animals lived on land, but in the oceans there were lives like microbes and the first forms of complex multicellular life. Scotland was then closer to the equator and had a semi-arid environment. The "Earth's landscape would have looked a little bit like Mars if there had been water on the surface," a publication from Oxford University reported on the research.

actual crater dimensions, "said Amor. "Crash craters on Earth are extremely rare and are quickly destroyed by erosion and plate tectonics or buried by sediments. The better we can understand how they formed, the better we can understand observations on the rocky planets and moons of the solar system. "

Ideally, Amor wants to perform a high-resolution 3D seismic survey in the Minch Basin between the Scottish mainland and the outer western islands. "Being offshore would be very expensive," he said.

As a final comment, Melosh said the presence of this crater in the UK illustrates the fact that no part of our planet is immune to meteorite impacts.

"Sooner or later – most of us hope later – a big impact will eventually reach the place where we live," he said.


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