Scientists discover an 8-mile-wide undersea crater created when the dinosaurs disappeared

No, it’s not that asteroid that doomed the dinosaurs to extinction, but a previously unknown crater 248 miles off the coast of West Africa that was created around the same time. Further study of the Nadir Crater, as it is called, could shake up what we know about that catastrophic moment in natural history.

Uisdean Nicholson, an assistant professor at Heriot-Watt University in Edinburgh, happened upon the crater by accident — he was reviewing seismic survey data for another project on the tectonic split between South America and Africa and found evidence of the crater under 400 meters of sediment from the seabed.

“While interpreting the data, I came across this very unusual crater-like feature, unlike anything I’d ever seen before,” he said.

To be absolutely sure that the crater was caused by an asteroid impact, he said it would be necessary to drill into the crater and test minerals from the crater floor. But it has all the features scientists would expect: the correct ratio of crater width to depth, the height of the rims and the height of the central buoyancy force — a mound in the center created by rock and sediment pushed up by the shock pressure.

The journal Science Advances published the study on Thursday.

“The discovery of a terrestrial impact crater is always important because they are very rare in the geological record. There are less than 200 confirmed impact structures on Earth and quite a few likely candidates that have not yet been unequivocally confirmed,” said Mark Boslough, a research professor in Earth and Planetary Sciences at the University of New Mexico. He was not involved in this research, but agreed that it was likely caused by an asteroid.

Boslough said the most important aspect of this discovery is that it was an example of a submarine impact crater, of which there are only a few known examples.

“The ability to study an underwater impact crater of this size would help us understand the process of ocean impacts, which are the most common but the least well-preserved or understood.”

A diagram with seismic observations and computer simulations of how Nadir Crater formed.

Cascading Effects

The crater is 5 miles (5 km) wide, and Nicholson believes it was likely caused by an asteroid more than 400 meters across crashing into the Earth’s crust.

Although much smaller than the city-sized asteroid that created the 100-mile-wide Chicxulub crater that slammed off the coast of Mexico and led to the mass extinction of much of the planet’s life, it’s still a pretty big deal. big space rock.

“The (Nadir) impact would have had serious repercussions locally and regionally – at least across the Atlantic,” Nicholson explained via email.

“There would have been a major earthquake (magnitude 6.5 – 7), so much ground shaking locally. The air blast would have been heard around the world and would itself have caused severe local damage throughout the region.

The asteroid that doomed the dinosaurs struck in the spring

It would have created an “exceptionally large” tsunami wave that stretched 1 kilometer high around the crater and would disappear to about five meters high once it reached South America.

By comparison, the 1908 mid-air explosion of a much smaller 50-meter-wide asteroid in Russia, known as the Tunguska event, flattened a forest over an area of ​​1,000 square kilometers.

“At about 400 meters, the air blast (which created the crater off West Africa) would have been orders of magnitude greater.”

Information from microfossils in nearby exploration wells shows that the crater was formed about 66 million years ago – at the end of the Cretaceous. However, there is still uncertainty – margin or error of about 1 million years – about the exact age.

Nicholson said it was possible that the asteroid’s impact was related to the Chicxulub impact, or that it was just a coincidence — an asteroid of this size would hit Earth every 700,000 years.

If linked, the asteroid could have been the result of the breakup of a parent asteroid near Earth – with the individual fragments scattered during a previous Earth orbit, or it could have been part of a longer-lasting rain of asteroids hitting Earth over a period of a million years or so.

430,000 years ago, a meteorite exploded in the sky over Antarctica

“Finding out the exact age is really crucial to testing this — again, only possible by drilling.”

Even if there was a connection, it would dwarf the Chicxulub impact, but it would still have contributed to the overall set of impacts, he said.

“Understanding the exact nature of the relationship to Chicxulub (if any) is important to understanding what was going on in the inner solar system at the time and raised some interesting new questions,” Nicholson said.

“If there were two impacts at the same time, would there be other craters and what was the cascading effect of multiple collisions?”

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