A novel study published in The Journal of Geology provides support for the theory that a cosmic impact event over North America some 13,000 years ago caused a major period of climate change known as the Younger Dryas stadial, or more famously, the “Big Freeze”.
Around 12,800 years ago, a sudden, catastrophic event plunged much of the Earth into a period of cold climatic conditions and drought. This drastic climate change‒ the Younger Dryas‒ coincided with the extinction of Pleistocene megafauna, such as the saber-tooth cats and the mastodon, and resulted in major declines in prehistoric human populations, including the dissolution of the Clovis culture.
Several rival theories have been proposed about the event that sparked this period, but with little evidence to prove their accuracy. These include a collapse of the North American ice sheets, a major volcanic eruption, and a solar flare.
However, in a study published in The Journal of Geology, an international group of scientists analysing existing and new evidence have determined a cosmic impact event, such a comet or a meteorite, to be the only plausible hypothesis to explain the cohort of unusual occurrences at the onset of the Younger Dryas period.
Researchers from 21 universities in 6 countries believe the key to the mystery of the Big Freeze resides in nanodiamonds scattered across Europe, North American, and portions of South America, in a 50-million-square-kilometer area known as the Younger Dryas Boundary (YDB) field.
Microscopic nanodiamonds, melt-glass, carbon spherules, and other high-temperature materials are found in copious amounts throughout the YDB field, in a thin layer located only meters from the Earth’s surface. As these materials formed at temperatures in excess of 2200 degrees Celsius, the fact that they are presented together so close to the Earth’s surface implies they were probably formed by a major extra-terrestrial impact event.
In addition to providing support for the cosmic impact event hypothesis, the study also offers evidence to reject alternate hypotheses for the formation of the YDB nanodiamonds, such as wildfires, volcanism, or meteroric flux.
The team’s findings serve to settle the debate about the presence of nanodiamonds in the YDB field and challenge existing paradigms across multiple disciplines, including impact dynamics, archaeology, palaeontology, limnology, and palynology.
Contributing Source: The University of Chicago Press
Header Image Source: Wikimedia
