TORONTO – Researchers believe they have found the cause of a dramatic and abrupt shift in the prehistoric global climate.
They say the cause was due to the impact of an asteroid or comet crashing into Quebec some 13,000 years ago.
The study, published in the Proceedings of the National Academy of Sciences (PNAS), found that the impact, which researchers say occurred at the beginning of the Younger Dryas period, wiped out many of Earth’s large mammals, including camels, giant sloths, saber-toothed cats and mastodons.
The cosmic impact also may have prompted human hunters to begin gathering and growing their food.
The Younger Dryas period was a relatively brief (around 1,300 years) span where the Earth returned to glacial conditions.
“The Younger Dryas cooling impacted human history in a profound manner,” said Dartmouth College professor and co-author of the study Mukul Sharma.
While there is no controversy over whether or not these environmental changes took place, the cause of these changes has long been disputed.
One theory is that an ice dam in North America ruptured, releasing a massive amount of water into the Atlantic Ocean. Proponents of this theory argue the influx of freshwater shut down ocean currents which move tropical water north.
But the Dartmouth researchers say they have found conclusive evidence linking a cosmic impact to the abrupt environmental changes.
“We have for the first time narrowed down the region where a Younger Dryas impact did take place, even though we have not yet found its crater,” said Sharma.
Sharma and his co-authors’ report focuses on tiny samples of molten rock found in Pennsylvania and New Jersey. Researchers said the geochemistry and mineralogy profiles are identical to rock found in Quebec, where they argue the cosmic impact took place.
Sharma said that the environmental shifts that took place in the Younger Dryas period were likely caused by “multiple concurrent impacts.”
“However, to date no impact craters have been found and our research will help track one of them down,” he said.
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