New evidence suggests that a comet explosion over North America may have triggered a massive wave of destruction nearly 13,000 years ago, killing off mammoths and mastodons and wiping out one of the continent’s oldest human cultures. Scientists found traces of extreme heat and pressure, including shocked quartz, buried in layers of ancient sediment.
The study, published in PLOS One, strengthens the case for what’s known as the Younger Dryas impact hypothesis. The idea? A fragmented comet blew up in Earth’s atmosphere, causing fires, a plunge in global temperatures, and possibly the sudden disappearance of the Clovis culture, a group of early hunters known for their distinctive stone tools.
Led by geologist James Kennett from UC Santa Barbara, the research team studied three key sites: Murray Springs (Arizona), Blackwater Draw (New Mexico), and Arlington Canyon (California). At each location, they found a unique mix of debris pointing to a massive and fast-moving disaster.
Signs of Fire and Impact Hidden in Ancient Layers
Across all three sites, scientists discovered a strange dark layer of earth called the “black mat.” It’s packed with carbon and sits right at the time when the Younger Dryas period started, when Earth suddenly got colder again after thousands of years of warming. According to the study, this layer also includes materials formed by high-energy explosions: nanodiamonds, metal bits, and melted rocks.
But what really caught the researchers’ attention was the shocked quartz, tiny sand grains that had been fractured and altered in a way that only happens under extreme pressure. Using powerful microscopes, the team saw melted veins inside the grains, ruling out volcanoes or human fires as the cause. The only thing that fits, they say, is something exploding with enormous force in the sky.
No Crater, But Plenty Of Chaos
You might expect a crater from such a dramatic event, but there isn’t one. That’s because, as noted by the researchers, this wasn’t a direct hit. The comet likely exploded in mid-air, causing a giant fireball that never touched the ground. It’s similar to what happened in Tunguska, Siberia in 1908, but on a much larger scale.
To test this theory, the team ran computer models showing how different kinds of airbursts could create the shock patterns found in the quartz samples and the results matched up.
Humans and Beasts: Wiped Out
Right after this event, two big things happened: most of North America’s large Ice Age animals vanished, and the Clovis people disappeared from the archaeological record. According to the study, the explosion probably triggered wildfires that filled the sky with dust and smoke. Sunlight got blocked, temperatures dropped again, and food sources collapsed.
The Clovis culture, once spread widely across the continent, left no trace after that point. Their stone tools just stop appearing. And the timing matches the extinction of mammoths, mastodons, and other giants that had ruled the land for thousands of years.
With all these clues, shocked quartz, black mats, impact debris, and the sudden collapse of species and cultures, the idea of a cosmic explosion is gaining more ground. As Kennett put it, when the comet hit, “all hell broke loose.”