Scientists have discovered an 8 km wide crater under the sea that emerged when the dinosaurs died out

No, not this asteroid, which wiped out the dinosaurs to extinction, but a previously unknown crater 248 miles off the coast of West Africa which was created around the same time. . Further study of Nader Crater, as it is called, could destabilize what we know about this disastrous moment in natural history.

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

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

To be absolutely sure the crater was caused by an asteroid impact, he said it would be necessary to drill into the crater and test for minerals from the crater floor. But it has all the distinguishing features scientists would expect: the correct ratio of crater width to depth, the height of the ridges, and the height of the central lift – a mound in the center caused by rocks and sediments. pushed by impact pressure. .

Mark said: “The discovery of a ground impact crater is always significant because it is so rare in the geological record. Boslough, research professor of Earth and planetary sciences at the University of New Mexico He was not involved in this research, but agreed that it could have been due to an asteroid.

The most significant aspect of this find, Boslough said, was that it was an example of an underwater impact crater, of which only a few known examples exist.

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

cascading consequences

The crater is eight kilometers (5 miles) wide and Nicholson believes it was likely caused by an asteroid more than 400 meters (1,300 feet) wide that entered the Earth’s crust.

Although much smaller than the city-sized asteroid that impacted the 100-mile-wide Chicxulub crater on the coast of Mexico This led to the mass extinction of much life on this planet, it’s still a very large space rock.

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

“There would have been a big earthquake (magnitude 6.5-7), and the ground shook a lot locally. The thunder of the airburst could have been heard around the world and caused severe local damage throughout the region.

The asteroid that killed the dinosaurs hit in the spring

It would have caused an “unusually large” tsunami 3,200 feet (1 kilometer) high around the crater, dissipating to a height of about five meters when it hit South America.

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

“At about 400 meters, the atmospheric eruption (which caused the West African crater) was much larger.”

Information on microfossils from nearby exploration wells show that the crater was formed around 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 – as to its exact age.

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

If the asteroid is tethered, it could have been the result of an original decay of near-Earth asteroids – with separate fragments scattered during the previous Earth orbit, or it could have been part of a shower long-lived asteroid that hit Earth around the corner. over a million years.

A meteorite exploded in the air over Antarctica 430,000 years ago

“Knowing the exact age is really crucial to testing this – again, this can only be achieved by digging.”

Even if it was related, he said, it could be mitigated by the Chicxulub effect, but it would have increased the overall cascading results.

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

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

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