November 17, 2025
Comet on Fire Meteor Earth
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Newly discovered shocked quartz at ancient Clovis sites bolsters evidence that a comet explosion 13,000 years ago unleashed widespread destruction, possibly wiping out Ice Age giants and early North American peoples. Credit: Stock
Evidence from key archaeological sites suggests a major cosmic explosion may have reshaped the climate and ecosystems of the late Pleistocene.
Scientists are expanding the evidence supporting the idea that a fragmented comet exploded over Earth nearly 13,000 years ago. This cosmic event may have played a part in the extinction of mammoths, mastodons, and many other large Ice Age animals, as well as the sudden disappearance of the Clovis culture from North America’s archaeological record.
In a study published in PLOS One, UC Santa Barbara Emeritus Professor of Earth Science James Kennett and his team report the discovery of shocked quartz (sand grains altered by intense heat and pressure) at three key Clovis sites in the United States: Murray Springs in Arizona, Blackwater Draw in New Mexico, and Arlington Canyon in California’s Channel Islands.
“These three sites were classic sites in the discovery and the documentation of the megafaunal extinctions in North America and the disappearance of the Clovis culture,” said Kennett.
Evidence for the Younger Dryas Impact hypothesis
The extinction of large Ice Age animals and the loss of the Clovis technocomplex occurred at the same time as the onset of the Younger Dryas, a sudden cooling period that interrupted the planet’s gradual warming after the Last Glacial Period. This unusual return to near–ice age conditions lasted for roughly a thousand years.
Scientists have suggested several possible causes for this dramatic climate shift. Kennett and his colleagues propose that a fragmented comet exploded in the atmosphere, releasing intense heat and shockwaves across the planet.
“In other words, all hell broke loose,” Kennett said. According to the Younger Dryas impact hypothesis, the explosions were responsible for widespread burning and the resulting smoke and soot, in addition to dust that blocked the sun, leading to an “impact winter.” Rapid melting of the ice sheets could have helped to further cool the impact zones. The shock of impact itself, followed by harsh conditions thereafter, may have contributed to the demise of the megafauna in both North and South America and the disappearance of the Clovis culture, according to the hypothesis.
Three Classic Clovis Archaeological Sites Graphic
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The three classic Clovis archaeological sites in the study. Credit: Courtesy image
Accumulating Evidence for an Impact Event
For the past couple of decades, Kennett and fellow proponents of this hypothesis have been gathering evidence that increasingly supports it, including a “black mat” layer in the sediment at many sites across North America and Europe — indicative of widespread burning. Additionally, they have uncovered a growing list of impact proxies, which include unusually high concentrations of rare minerals that are common in comets, such as platinum and iridium, and mineral formations indicative of extremely high temperatures and pressures, such as nanodiamonds and metals and minerals that have melted, cooled, and hardened again, including metallic spherules and meltglass.
Thanks to advances in technology, the team is homing in on another proxy that is considered the crème de la crème of cosmic impact evidence: shocked quartz — grains of sand that exhibit deformations due to extreme heat and temperature. In samples from the three North American archaeological sites — Murray Springs, Blackwater Draw and Arlington Canyon — the researchers identified quartz grains with telltale cracks, some filled with melted silica. They used a variety of techniques, including electron microscopy and cathodoluminescence, to confirm that the quartz grains had been shocked at extremely high temperatures and pressures, far beyond what could have been accomplished by volcanism or ancient human activity.
Airbursts and the Challenge of Craterless Impacts
The presence of shocked quartz is particularly important in the absence of craters — the smoking gun of cosmic impact evidence. Unlike the asteroid that killed off the dinosaurs 65 million years ago and left a crater beneath the Yucatan Peninsula, “touchdown airbursts” — cosmic collisions that occur above the Earth’s surface, such as from this proposed fragmented comet — leave little, if any, evidence on the landscape. Using hydrocode modeling, the team modeled these low-altitude, above-ground explosions and the variety of impacts that could lead to the shock patterns in the quartz grains.
nbs said. While the accepted evidence for cosmic impact leans heavily on the parallel cracks in quartz found at craters, the variety of directions, pressures, and temperatures that emerge around airbursts would lead to variations in the shock patterns in the quartz, he explained. “There are going to be some very highly shocked grains and some that will be low-shocked. That’s what you would expect.”
Added to the other impact proxies found in the same layer of sediment — carbon-rich black mat, nanodiamonds, impact spherules — and found at three key archaeological sites, the discovery of these shocked quartz grains “supports a cosmic impact as a major contributing factor in the megafaunal extinctions and the collapse of the Clovis technocomplex at the Younger Dryas onset,” according to the paper.
Reference: “Shocked quartz at the Younger Dryas onset (12.8 ka) supports cosmic airbursts/impacts contributing to North American megafaunal extinctions and collapse of the Clovis technocomplex” by James P. Kennett, Malcolm A. LeCompte, Christopher R. Moore, Gunther Kletetschka, John R. Johnson, Wendy S. Wolbach, Siddhartha Mitra, Abigail Maiorana-Boutilier, Victor Adedeji, Marc D. Young, Timothy Witwer, Kurt Langworthy, Joshua J. Razink, Valerie Brogden, Brian van Devener, Jesus Paulo Perez, Randy Polson and Allen West, 10 September 2025, PLOS ONE.
DOI: 10.1371/journal.pone.0319840
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