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Some 13,000 years ago, as Earth was warming at the end of the last Ice Age, a strange thing happened: all of a sudden, the planet went cold again. The cause of this millennia-long anomaly, known as the Younger Dryas period, has long been a mystery: the prevailing theory has been that it was caused by a disruption to ocean circulation, but other theories have been put forward, such as a volcanic eruption or an extraterrestrial impact event.

That latter theory was for some time seen as a bit of a fringe idea – our good friend, alternative history author Graham Hancock, was on the case years ago with his book Magicians of the Gods (Amazon US/Amazon UK). But in recent years the evidence has been mounting in mainstream academia that it may indeed have been the cause. Last year, two scientific papers offered supporting evidence for an impact event – one pointed out raised levels of platinum in sediment of that period, the other identifying that the Carolina Bays may in fact be residual impact craters.

And now, another study – so wide-ranging that it has been split into two separate papers – provides more support for the theory that a massive impact event happened around 10,800 BCE. Part one of the paper, titled “Extraordinary Biomass-Burning Episode and Impact Winter Triggered by the Younger Dryas Cosmic Impact ∼12,800 Years Ago”, discusses ice core evidence for a huge conflagration that set fire to close to a tenth of the Earth:

In four ice-core sequences from Greenland, Antarctica, and Russia…anomalous peaks in other combustion aerosols occur, including nitrate, oxalate, acetate, and formate, reflecting one of the largest biomass-burning episodes in more than 120,000 y. In support of widespread wildfires, the perturbations in CO2 records from Taylor Glacier, Antarctica, suggest that biomass burning at the Younger Dryas onset may have consumed ∼10 million km2, or ∼9% of Earth’s terrestrial biomass.

Part two of the study then provides supporting evidence from a separate source: sedimentary analysis. Scientists studied charcoal and soot records from 152 lakes, as well as marine cores, and terrestrial sequences, which revealed “a major peak in biomass burning at the Younger Dryas (YD) onset that appears to be the highest during the latest Quaternary” ( the last 2.6 million years). The concentrations of soot from this time again suggest that fires consumed around 10 million km2 of Earth’s surface, or ∼9% of Earth’s biomass. This is, the study notes, considerably more even than it was for the ‘dinosaur-killing’ K-Pg impact event 66 million years ago, which caused a mass extinction of three-quarters of the plant and animal species on Earth.

The study concludes that this massive inferno, caused by a comet fragmenting into many pieces before impacting the Earth, resulted in extensive atmospheric soot/dust loading that triggered an “impact winter”, which explains the anomalous cooling period and other climate changes of the Younger Dryas period.

More details about the new study can be found in this press release from the University of Kansas.