Jan Bartek – AncientPages.com – Researchers are expanding on evidence suggesting that a fragmented comet exploded over Earth nearly 13,000 years ago, potentially contributing to the extinction of mammoths, mastodons, and other megafauna, as well as the disappearance of the Clovis culture in North America.
Credit: Pixabay – Willi-van-de-Winkel- Public Domain
In a recent study, UC Santa Barbara Emeritus Professor of Earth Science James Kennett and his team reported finding shocked quartz—sand grains altered by intense pressure and heat—at three key Clovis archaeological sites: Murray Springs in Arizona, Blackwater Draw in New Mexico, and Arlington Canyon on California’s Channel Islands. According to Kennett, these sites were pivotal in understanding both the megafaunal extinctions and the decline of the Clovis culture.
The loss of these species and cultural elements aligns with the onset of the Younger Dryas period—a sudden return to near-ice-age conditions that lasted approximately a thousand years during an otherwise warming phase following the Last Glacial Period. While several theories exist regarding the trigger of this event, Kennett’s team suggests that an above-ground explosion from a fragmented comet could have sent shockwaves and extreme heat across the Earth.
“In other words, all hell broke loose,” Kennett said.
The Younger Dryas impact hypothesis proposes that massive explosions triggered extensive fires, producing smoke and soot, as well as dust that obscured sunlight, leading to a “impact winter.” This phenomenon may have been exacerbated by the rapid melting of ice sheets, further cooling the affected areas. The initial shock and subsequent harsh conditions are believed to have contributed to the extinction of megafauna in both North America and South America, as well as the disappearance of the Clovis culture.
Over recent decades, researchers like Kennett have amassed evidence supporting this hypothesis. They have identified a “black mat” layer in sediments across numerous sites in North America and Europe, indicative of widespread burning. Additionally, they have discovered various impact proxies—such as elevated levels of rare minerals like platinum and iridium typically found in comets—and mineral formations created under extreme temperatures and pressures. These include nanodiamonds, as well as metals and minerals that underwent melting, cooling, and solidification processes, such as metallic spherules and melt glass.
Thanks to technological advances, the team is focusing on a prime proxy for cosmic impacts: shocked quartz. These sand grains show deformations from extreme heat and pressure.
At three North American sites—Murray Springs, Blackwater Draw, and Arlington Canyon—the researchers found quartz grains with distinctive cracks, some filled with melted silica. Using electron microscopy and cathodoluminescence, they confirmed these grains were shocked at temperatures and pressures beyond what volcanism or human activity could cause. Shocked quartz is crucial when craters are absent as evidence of cosmic impact.
Unlike the asteroid that created a crater under the Yucatan Peninsula 65 million years ago, “touchdown airbursts” — collisions above Earth’s surface, such as those from fragmented comets —leave minimal landscape evidence. The team used hydrocode modeling to study these explosions and their effects on quartz shock patterns.
Researchers found shocked quartz from the Younger Dryas at three Clovis sites in the USA. Credit: USGS
“There are different levels of shocked quartz,” Kennett 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.”
The study highlights that the discovery of shocked quartz grains, alongside other impact indicators such as carbon-rich black mat, nanodiamonds, and impact spherules found in the same sediment layer at three significant archaeological sites, supports the theory of a cosmic impact. This event is considered a major contributing factor to both the megafaunal extinctions and the collapse of the Clovis technocomplex at the onset of the Younger Dryas period.
The study was published in the journal PLOS One
Written by jan Bartek – AncientPages.com Staff Writer