The cause of a thousand-year cold period that killed off giant ground sloths, mastodons, and sabretooth cats continues to be in contention. While it's long been hypothesized that the major climate shift that occurred around 12,900 years ago was the result of a sudden flood of freshwater into the Atlantic, new research is trying to shift the cause to a comet or asteroid that it suggests crashed down in Quebec.
An impact site is yet to be found, but the Dartmouth College team behind the research says that it's identified fragments of solidified molten rock that seem to have been thrown all the way from Quebec to Pennsylvania and New Jersey because of such an explosion. The rocks appear to have been deposited at the dawn of the period of climate change, and are apparently consistent with what would have been expelled from a cosmic body colliding with the earth.
Now they just have to find a crater
“This is unequivocal evidence for an impact with Earth,” Mukul Sharma, a coauthor of the study, tells Nature.
The time period, known as the Younger Dryas, marked the disappearance of large animals and the transformation of their human hunters into gatherers who foraged for roots and berries to further substantiate their new diet of small game. Similar findings have been proposed in the past, but Dartmouth's researchers say they're the first to identify where such a major impact could have occurred. "We have for the first time narrowed down the region," Sharma says in a statement.
Sharma's theory still remains the underdog. Finding an actual crater could be critical to backing it up, and Sharma suggests that there may actually have been several different impacts — and therefore several different craters. A physicist who spoke with Nature says that such an impact would be so large that it would be hard to dispute, but that it also raises the question of why nothing has been found. Sharma's next step is putting together a plan to find one, and he says that his team's findings should be key: "Our research will help track one of them down."