An asteroid from outer space struck Earth’s surface 66 million years ago, leaving a huge crater beneath the ocean and wreaking havoc on the planet.
No, it wasn’t the asteroid that wiped out the dinosaurs, but a previously unknown crater 248 miles off the coast of West Africa, which was formed around the same time. Further study of Nadar Crater, as it is called, may confuse what we know about this devastating moment in natural history.
Eusedin Nicholson, assistant professor at Heriot-Watt University in Edinburgh, happened to stumble upon the crater – he was reviewing seismic survey data for another project on the tectonic divide between South America and Africa and 400 meters of seafloor sediment. Evidence of a crater was found below. ,
“When interpreting the data,[saya menemukan]This is a very unusual crater-like feature, unlike anything I’ve seen before,” he said.
“It has all the characteristics of a crater.”
To be absolutely sure that the crater was caused by an asteroid impact, he said it was necessary to drill the crater and test minerals from the bottom of the crater. But it has all of the typical features scientists expect: the perfect ratio of crater width to depth, mountain height and central uplift height—the mound in the center caused by rock and sediment being pushed up by impact forces.
The study was published Thursday in the journal Science Advances.
“The discovery of archaeological craters is always important, as it is so rare in the geological record. There are less than 200 confirmed impact structures on Earth and very few potential candidates remain to be discovered,” said Mark Boslaug, a research professor. in Earth and Planetary Science at the University of New Mexico. Confirm them definitively.” He was not involved in the study, but agrees it may have been caused by an asteroid.
The most important aspect of the discovery, Boslow said, is that it is an example of an underwater impact crater, of which only a few examples are known.
“The opportunity to study underwater craters of this size will help us understand ocean impact processes, which are more common but less well preserved and understood.”
The crater is 8 kilometers (5 mi) wide, and Nicholson believes it is likely caused by an asteroid more than 400 meters (1,300 ft) wide in the Earth’s crust.
Although much smaller than the city-sized asteroid that caused the 100-mile-wide Chicxulub crater off the Mexican coast and wiped out most of the planet’s life, it is still a large space rock.
“The impact (rarely) has serious consequences locally and regionally – at least in the Atlantic,” Nicholson explained by email.
“There will be a major earthquake (magnitude 6.5-7), and thus the ground will shake locally. The rumble of the air blast could be heard all over the world, and in itself would cause severe local damage throughout the region. ,
This would have produced a “very large” tsunami of 3,200 feet (1 kilometer) around the crater, which after reaching South America would have spread to a height of about five meters.
For comparison, in Russia in 1908 a 50-meter-wide asteroid atmospheric explosion, known as the Tunguska He event, razed a forest over an area of 1,000 square kilometers.
“At 400 meters or more, the atmospheric eruption (which caused the West African crater) was enormous.
Information from microfossils in nearby exploration wells suggests that the crater was formed around 66 million years ago – at the end of the Cretaceous period. However, there is still uncertainty – a difference or error of about a million years – about its exact age.
It’s possible that the asteroid impact was related to the Chicxulub impact, or just a coincidence — an asteroid of this size would strike Earth every 700,000 years, Nicholson said.
If the asteroid is bound, it may be the result of the disintegration of the original near-Earth asteroid – with isolated fragments scattered during its past Earth orbit, or it may be part of a longer-lived asteroid rain. Which hits the earth in a period. Time. One million years or more.
“Testing this requires knowing the exact age—again, this can only be obtained by digging.”
Even if it is related, he said, it may be less of a Chicxulub effect, but it would add up to a whole set of broader consequences.
“Understanding the precise nature of the association with Chicxulub (if any) is critical to understanding what was happening in the inner solar system at the time and raises some interesting new questions,” Nicholson said.
“If two collisions happen at the same time, there could be another crater, and what is the wider impact of multiple collisions?”