The Greenland Impact Crater is 58 million years old

Scientists have done field work at the edge of the Greenland ice cap.

Scientists have done field work at the edge of the Greenland ice cap.
Photo: Pierre Beck

The hidden crater in northwest Greenland is about 58 million years old, making it much older than previous estimates. The challenge now will be to find more evidence of what was surely a massively devastating global event.

Dating the sand and rock associated with the impact event enabled an international team of researchers to derive the new estimate. The Greenland crater, which is 19 miles (31 kilometers) wide, was discovered just seven years ago. It is buried under 3200 mphthick t (1000 meters) Hiawatha Glacier, making it a difficult being study.

“We were very surprised that the crater was 58 million years old,” Nikolai Larsen, a geologist at the University of Copenhagen and co-author of the new study, told me in an email. “All the circumstantial evidence we have so far indicates that the crater was much smaller and from a period when the Greenland ice sheet was present.”

The location of the 19-mile (31 kilometer) wide impact crater in northwest Greenland.

Location width 19 miles (31-kilometerImpact crater in northwest Greenland.
picture: The Natural History Museum in Denmark

Larsen and colleagues first figured That crater was somewhere between 3 million and 1,200 years ago. The apparent newness of the effect during the late Pleistocene presented a tantalizing possibility, as it indicated that humans were affected by the event. You also likely spoke to the Younger Dryas period, a cooling phase that began about 12,900 years ago. butit’s new ResearchPublished today in Science Advances, it notes that the effect did not affect humans, nor did it precipitate the younger Dryas. Regarding the actual effects of the effect, this is a question that needs to be answered now.

Greenland ice sheet formed between 2 million and 3 Millions of years ago, long after the iron-rich asteroid collided with what is now northwest Greenland. At the time of impact, Greenland was characterized by temperate rainforest and a diverse environment. The crater – which ranks among the 25 largest asteroid holes on Earth – has been buried in ice over time, which is why I just discovered it Recently and completely by accident.

Larsen was checking maps of Greenland in 2015 when he noticed a circular feature in the rock below Hiawatha Glacier. Subsequent surveys using ground-penetrating radar, or in this case ice-penetrating radar, confirmed the existence of the impact structure, resulting in 2018. paper Announcing his discovery.

The crater is so old came as a big surprise to the team, which included researchers from Denmark’s Natural History Museum, the GLOBE Institute at the University of Copenhagen, and the Swedish Museum of Natural History in Stockholm. Pre-existing evidence, though circumstantial, points to a relatively recent event, where the shape of the crater appears to be “relatively new,” the ice layers contain disturbed ice from the last Ice Age, and material from the area contains organic remains from a boreal forest – Larsen said: “The last time a boreal forest grew in northern Greenland was two to three million years ago.”

Team members conduct fieldwork along the edge of the Greenland ice sheet in 2019.

Team members conduct fieldwork along the edge of the Greenland ice sheet in 2019.
Photo: Joe McGregor

What Larsen and his colleagues really needed were samples from the crater – not an easy task given the 1,000 feet of ice accumulating on top of it. Instead, the team visited remote areas across three field seasons to find suitable dating material, specifically impact rocks found in glacial debris behind the ice cap.

This was not an easy task, said Larsen. Because field work in remote northern Greenland is very difficult and expensive.” The key to the new research was the collection of partially melted sand and shocked zircon crystals, which were delivered downstream of the crater by meltwater.

At NHM in Denmark, scientists used lasers to heat grains of sand until they released argon gas, while a team at Sweden’s MNH used uranium and lead dating of zircon. Both methods yielded the same result, providing the new estimate of effect.

Dating the shocked zircon crystals was one of two methods used to come up with a new estimate of the effect.

Dating the shocked zircon crystals was one of two methods used to come up with a new estimate of the effect.
picture: University of Copenhagen

The challenge going forward will be for scientists to connect this event with other lines of evidence linked to the impact. The asteroid smashed into northwest Greenland about 8 million years after the dinosaurs went extinct, and given the size of the asteroid – about 0.6 miles (1 kilometer) wide– It would have upset the global climate to a great extent.

“Our next step is to examine the 58-million-year-old Paleocene geological sections to see if we can identify the impact signal,” Larsen said. “This is important if we want to understand whether an impact of this magnitude altered the Earth’s climate or led to any mass extinctions, which we suspect will happen.”

The new paper adds further clarity to this remarkable event, while opening new avenues for future research. Undoubtedly, this ancient Greenland wound still has many stories to tell.

more: Scientists discover an ancient lake lake under the ice of Greenland.

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