29 Mar Discovering the Location of the Largest Asteroid Impact in Britain
The location of the biggest asteroid impact to ever hit Britain was discovered by researchers at Oxford and Aberdeen universities. The massive impact occurred 1.2 billion years ago, in a spot now under the sea between mainland Scotland and the Outer Hebrides. In 2008, the researchers found signs of the collision during a field trip in Scotland, but it wasn’t until recently that they were able to pinpoint the exact location.
Testing Rocks to Trace the Impact
Tests on rocks near Ullapool in northwest Scotland revealed that an object approximately one mile wide crashed into the Minch, a strait separating the mainland from the northern Inner Hebrides. The violent 38,000 mph collision created a 12-mile-wide crater in the ground. At the time of the impact, Scotland was a semi-arid land near the equator, and most life on Earth was still in the oceans.
“The impact would have sent huge clouds of dust and gas in all directions from the impact site,” said Ken Amor, the lead researcher from Oxford. The crater is now submerged in 200-meter-deep water and covered in sediment.
Uncovering the Evidence
The first evidence of the impact was discovered over a decade ago when Amor was assisting undergraduates on a geology field trip in the Scottish Highlands. During their trip, they stopped in Stoer, a small village, to inspect an unusual rock formation known as the Stac Fada member (SFM). Initially, the red sandstone was thought to have come from a volcano, but Amor noticed that “strange green blobs” in the rock were similar to an impact crater in Nördlingen, Germany.
After taking samples back to Oxford, Amor found strong evidence of an asteroid strike, including quartz crystals deformed by the shock of impact and high levels of platinum and palladium, metals commonly found in meteorites. With the help of colleagues at Exeter University, Amor was able to trace the impact crater by using three independent techniques. Their findings have been published in the Journal of the Geological Society.
Potential for Further Study
It is possible to detect the impact crater with a seismic reflection survey similar to those used by oil prospecting companies. Further studies of the rock may also enable scientists to trace the meteorite back to a family of asteroids still orbiting the sun. Although the frequency of impacts this size is unknown, it is believed that asteroids of this size strike Earth once every 100,000 to 1 million years. While the impact in Scotland was dramatic, it was minor compared to the impact in Mexico’s Yucatán peninsula 66 million years ago, which caused the extinction of the dinosaurs.
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