Prehistoric Climate Change Linked with Cosmic Impact in Canada, Researchers Say

A comet or asteroid that landed at Quebec, Canada, might have led to the drastic climate change about 12,900 years ago, according to a new study.

The study was conducted by researchers at Dartmouth College and their colleagues. Their research challenges the idea that the Younger Dryas stadial or the Big Freeze was caused by rise in meltwater from the North American ice sheet. According to them, an object from space, a comet or asteroid was behind the dramatic shift in climate across the world.

Younger Dryas is named after a flower called Dryas octopetala, which is known to grow in cold conditions. This flower grew all over Europe during the period.

The event occurred about 12,900 years ago, when many parts of the Northern Hemisphere saw abrupt cooling followed by long periods of drought. In North America, many large animals such as camels, giant ground sloths, mastodons and saber-toothed cats disappeared. A group of humans known as the Clovis people stopped hunting and took-up nomadic lifestyle, eating roots, berries and smaller animals.

"The Younger Dryas cooling is a very intriguing event that impacted human history in a profound manner," says Mukul Sharma, a professor in the Department of Earth Sciences and one of the authors. "Environmental stresses may also have caused Natufians in the Near East to settle down for the first time and pursue agriculture."

Until recently, many researchers believed that the event was caused by the collapse of North American Ice sheets. In the present study, researchers focused on spherules, which are droplets of solidified molten rock released by the comet when it landed on earth. The spherules in the study were obtained from the boundary layers of Younger Dryas in Pennsylvania and New Jersey. Researchers then compared the geochemistry and mineral composition of these spherules to that of rocks found in Southern Quebec. They found that both rock samples were similar.

Corossal crater found in Quebec is an impact crater. However, researchers said that this crater isn't the impact site for rocks found in the sites at New Jersey and Pennsylvania.

"What is exciting in our paper is that we have for the first time narrowed down the region where a Younger Dryas impact did take place," Sharma said in a news release, "even though we have not yet found its crater."

The study is published in the Proceedings of the National Academy of Sciences (PNAS).