Giant impact crater in Greenland occurred a few million years after
dinosaurs went extinct

Date:
March 9, 2022
Source:
University of Copenhagen - Faculty of Science
Summary:
Danish and Swedish researchers have dated the enormous Hiawatha
impact crater, a 31 km-wide meteorite crater buried under a
kilometer of Greenlandic ice. The dating ends speculation that the
meteorite impacted after the appearance of humans and opens up a
new understanding of Earth's evolution in the post-dinosaur era.



FULL STORY ========================================================================== Danish and Swedish researchers have dated the enormous Hiawatha impact
crater, a 31 km-wide meteorite crater buried under a kilometer of
Greenlandic ice. The dating ends speculation that the meteorite impacted
after the appearance of humans and opens up a new understanding of
Earth's evolution in the post- dinosaur era.


==========================================================================
Ever since 2015, when researchers at the University of Copenhagen's GLOBE Institute discovered the Hiawatha impact crater in northwestern Greenland, uncertainty about the crater's age has been the subject of considerable speculation. Could the asteroid have slammed into Earth as recently
as 13,000 years ago, when humans had long populated the planet? Could
its impact have catalyzed a nearly 1,000-year period of global cooling
known as the Younger Dryas? New analyses performed on grains of sand
and rocks from the Hiawatha impact crater by the Natural History Museum
of Denmark and the GLOBE Institute at the University of Copenhagen, as
well as the Swedish Museum of Natural History in Stockholm, demonstrate
that the answer is no. The Hiawatha impact crater is far older. In fact,
a new study published in the journal Science Advances today reports its
age to be 58 million years old.

"Dating the crater has been a particularly tough nut to crack, so it's
very satisfying that two laboratories in Denmark and Sweden, using
different dating methods arrived at the same conclusion. As such, I'm
convinced that we've determined the crater's actual age, which is much
older than many people once thought," says Michael Storey of the Natural History Museum of Denmark.

"Determining the new age of the crater surprised us all. In the future,
it will help us investigate the impact's possible effect on climate
during an important epoch of Earth's history" says Dr. Gavin Kenny of
the Swedish Museum of Natural History.

As one of those who helped discover the Hiawatha impact crater in 2015, Professor Nicolaj Krog Larsen of the GLOBE Institute at the University
of Copenhagen is pleased that the crater's exact age is now confirmed.



==========================================================================
"It is fantastic to now know its age. We've been working hard to find
a way to date the crater since we discovered it seven years ago. Since
then, we have been on several field trips to the area to collect samples associated with the Hiawatha impact," says Professor Larsen Age revealed
by laser beams and grains of sand No kilometer-thick ice sheet draped
Northwest Greenland when the Hiawatha asteroid rammed into Earth surface releasing several million times more energy than an atomic bomb. At the
time, the Arctic was covered with a temperate rainforest and wildlife
abounded -- and temperatures of 20 degrees Celsius were the norm. Eight
million years earlier, an even larger asteroid struck present- day Mexico, causing the extinction of Earth's dinosaurs.

The asteroid smashed into Earth, leaving a thirty-one-kilometer-wide, one- kilometer-deep crater. The crater is big enough to contain the entire
city of Washington D.C. Today, the crater lies beneath the Hiawatha
Glacier in Northwest Greenland. Rivers flowing from the glacier supplied
the researchers with sand and rocks that were superheated by the impact
58 million years ago.

The sand was analyzed at the Natural History Museum of Denmark by heating
the grains with a laser until they released argon gas, whereas the rock
samples were analyzed at the Swedish Museum of Natural History using uranium-lead dating of the mineral zircon.

Clear evidence that the Hiawatha impact disrupted global climate is still lacking. However, the crater's dating allows the international research
team working on the crater to begin testing various hypotheses to better understand what its impact was on both the local and global climate.

Facts:
* At 31 km across, the Hiawatha impact crater is larger than about
90% of
the roughly 200 previously known impact craters on Earth.

* Although the Hiawatha impact crater is much smaller than the
approximately 200 km-wide Chicxulub impact crater in present-day
Mexico, which led to the demise of the dinosaurs, it would have
devastated the region and may even have had wider consequences
for the climate and plant and animal life.

* When the Hiawatha impact occurred 58 million years ago the Earth had
recovered from the catastrophic effects of the Chicxulub impact
eight million years earlier and was entering a long-term warming
trend that was to last about 5 million years.


========================================================================== Story Source: Materials provided by University_of_Copenhagen_-_Faculty_of_Science. Note: Content may be
edited for style and length.


========================================================================== Related Multimedia:
* Hiawatha_impact_crater ========================================================================== Journal Reference:
1. Gavin G. Kenny, William R. Hyde, Michael Storey, Adam A. Garde,
Martin J.

Whitehouse, Pierre Beck, Leif Johansson, Anne Sofie So/ndergaard,
Anders A. Bjo/rk, Joseph A. MacGregor, Shfaqat A. Khan,
Je're'mie Mouginot, Brandon C. Johnson, Elizabeth A. Silber,
Daniel K. P. Wielandt, Kurt H.

Kjaer, Nicolaj K. Larsen. A Late Paleocene age for Greenland's
Hiawatha impact structure. Science Advances, 2022; 8 (10) DOI:
10.1126/ sciadv.abm2434 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220309140838.htm

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