Those looking to bolster their argument that not all climate change is manmade may have received an early Christmas gift – researchers have found a massive hidden asteroid impact crate under Greenland whose age coincides with the beginning of a previously unexplained cooling period about 12.000 years ago. Does this change everything?
"The crater is exceptionally well-preserved, and that is surprising, because glacier ice is an incredibly efficient erosive agent that would have quickly removed traces of the impact. But that means the crater must be rather young from a geological perspective.”
In a press release announcing the study “A large impact crater beneath Hiawatha Glacier in northwest Greenland” published in the current edition of Science Advances, co-author Professor Kurt H. Kjær from the Center for GeoGenetics at the Natural History Museum of Denmark describes how researchers first found signs pointing to the existence of the crater under Greenland’s ice sheet in July 2015. It was not far from where a 20-ton iron meteorite had been discovered, but that wasn’t enough to connect the dots.
A German research plane from the Alfred Wegener Institute flew over the Hiawatha Glacier and, using a new ice radar system, was able to better image the depression and added to the evidence, exciting NASA glaciologist Joseph MacGregor. (Pictures here.)
“A distinctly circular rim, central uplift, disturbed and undisturbed ice layering, and basal debris. It's all there."
Surface expeditions in 2016 and 2017 collected samples of sediment washed out from under the depression and found the missing link.
"Some of the quartz sand washed from the crater had planar deformation features indicative of a violent impact, and this is conclusive evidence that the depression beneath the Hiawatha Glacier is a meteorite crater."
The crater measures more than 31 km (19.25 miles) in diameter, which puts the size of the iron meteorite at 1 km (.6 miles) wide and puts the impact in the top 25 of Earth impact craters, making it a good candidate for causing ecological disasters. Ice layers show it’s at least 12000 years old and rock erosion samples say it’s no more than 3 million years old.
It’s the more recent date that has scientists linking the event to the Younger Dryas period – a sudden unexplained cooling during a time of global warming after the last ice age. Occurring about 12,900 to 11,700 years ago, geological records in the Northern Hemisphere indicate a swift drop in temperatures of 2 to 6 degrees Celsius (3.6 to 10.8 degrees Fahrenheit), increases in glacier ice and cold waters in the Atlantic and general drier conditions. While the cooling was widespread, a few areas, southeastern North America for one, had a slight warming. The Younger Dryas coincided with a number of human cultures shifting from hunting and nomadic life to agriculture and settlements. In North America, the Clovis culture declined and a number of animal species went extinct.
All of these things could certainly have been caused by a meteor impact of catastrophic size. Is that the answer to the cause of the Younger Dryas that scientists have been searching for?
"The next step in the investigation will be to confidently date the impact. This will be a challenge, because it will probably require recovering material that melted during the impact from the bottom of the structure, but this is crucial if we are to understand how the Hiawatha impact affected life on Earth."
Sounds like Kjær is making his plans for next summer. Pack a parka, professor!