Huge underwater crater discovered after extinction of dinosaurs

An asteroid from outer space crashed into the surface of the Earth 66 million years ago, leaving a massive crater underwater and wreaking havoc on the planet.

No, this is not the asteroid that doomed the dinosaurs to extinction, but a previously unknown crater 248 miles off the coast of West Africa, formed around the same time. Further study of the so-called Nadir crater could overturn what we know about this cataclysmic moment in natural history.

Wisdeen Nicholson, assistant professor at Heriot-Watt University in Edinburgh, he was reviewing seismic data for another project on the tectonic split between South America and Africa and found evidence of a crater at a depth of 400 meters, under sediment on the seafloor.

“While interpreting the data, I (stumbled upon) this very unusual crater-like feature, unlike anything I have ever seen before,” he said.

To be absolutely sure that the crater was caused by an asteroid impact, he said that it would be necessary to drill into the crater and check the minerals at the bottom of the crater. But it has all the distinguishing features that scientists expect: the correct ratio of the width of the crater to depth, the height of the edges and the height of the central uplift – a mound in the center formed by rocks and sediments raised by impact pressure. .

The journal Science Advances published the study.

“Finding a terrestrial impact crater is always of great importance 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 received unequivocal confirmation, ”said Mark. Boslow, Research Professor of Earth and Planetary Sciences at the University of New Mexico. He was not involved in this study, but agreed that it was likely caused by an asteroid.

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

“Being able to study an underwater crater of this size will help us understand the process of ocean impacts, which are the most common but the least well preserved or studied.”

The crater is 8 kilometers (5 miles) wide, and Nicholson believes it was likely caused by an asteroid over 400 meters (1,300 feet) wide that crashed into the Earth’s crust.

Although much smaller than the city-sized asteroid that created the 100-mile-wide Chicxulub crater that formed off the coast of Mexico and led to the mass extinction of most life on the planet, it is still a fairly large space rock.

“A collision (nadir) would have major local and regional repercussions – at least across the Atlantic Ocean,” Nicholson explained via email.

“There would be a strong earthquake (magnitude 6.5-7), such a strong local shaking of the earth. The airburst would have been heard around the world and by itself would have caused severe localized damage throughout the region.

This would have generated an “exceptionally large” 3,200-foot (1 kilometer) tsunami around the crater, which would have dissipated to a height of about five meters when it reached South America.

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