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They discover an underwater crater that originated when the dinosaurs disappeared

They discover an underwater crater that originated when the dinosaurs disappeared

(CNN) – An asteroid collided with the Earth’s surface 66 million years ago, leaving a huge crater under the sea that wreaked havoc on the planet.

No, it wasn’t the asteroid that wiped out the dinosaurs, but the previously unknown crater 400 kilometers (248 miles) off the coast of West Africa was created around the same time. Further study of the Nadir Crater, as it is called, could revolutionize what we know about that disastrous moment in natural history.

Osden Nicholson, an assistant professor at Heriot-Watt University in Edinburgh, stumbled across the crater by chance: He was reviewing seismic survey data for another project on the tectonic split between South America and Africa and found evidence of the crater below 400 metres. Sea floor sediments.

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

“It had all the characteristics of a crater.”

To be absolutely sure that the crater was caused by an asteroid impact, he said that it would be necessary to drill in it and test minerals on the floor of the crater. But it has all the features scientists would expect: the right ratio between crater width and depth, the height of the edges and the height of the central jack, a mound in the middle caused by pressure-driven rocks and sediments. of influence.

magazine Science Advances published the study Wednesday.

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

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

“The opportunity to study a crater of this size will help us understand the process of ocean impacts, which are more common but less well preserved and understood.”

A schematic diagram, including seismic observations and computer simulations, of how the Nader Crater formed.

Multiple consequences

The crater is 8 kilometers (5 miles) wide, and Nicholson believes it may have been caused by an asteroid over 400 meters (1,300 feet) wide that collided with the Earth’s crust.

While it is much smaller than the city-sized asteroid that caused the 100-mile (160 kilometer) Chicxulub crater to slam into the coast of Mexico and cause the mass extinction of much of life on the planet, it is still very large. space rock.

“The (rare) impact has had dire consequences both locally and regionally, at least across the Atlantic,” Nicholson explained by email.

“There was a large earthquake (magnitude 6.5-7), which was so large that it shook the earth locally. The thunder of the air blast could be heard all over the world and caused severe local damage throughout the region.”

It would have caused an “exceptionally large” tsunami of up to one kilometer (3,200 feet) around the crater, fading to about five meters in height once it reached South America.

In comparison, the atmospheric explosion of a much smaller 50-meter-wide asteroid in 1908 in Russia, known as Tunguska eventdestroyed a forest in an area of ​​​​1,000 square kilometers.

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“At 400 metres, the atmospheric explosion (which caused the West African crater) was much larger.”

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

It’s possible, Nicholson said, that the asteroid impact is related to the Chicxulub effect, or it could just be a coincidence: an asteroid of this size will strike Earth every 700,000 years.

In the case of association, the asteroid could be the result of the disintegration of an original asteroid near Earth, with separate fragments scattered during a previous Earth orbit, or it could be part of an Earth-hit asteroid shower. million years or so.

“Knowing the exact age is crucial to testing this, again it is only possible by drilling.”

He said that even if it had been linked, it would have been overshadowed by the influence of Chicxulub, but it would have added to the overall set of multiple consequences.

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

“If there are two collisions at the same time, can there be other craters and what is the cascading effect of multiple collisions?”