Scientists have uncovered shocked quartz at key Clovis-era sites, strengthening evidence that a comet explosion around 13,000 years ago contributed to the extinction of mammoths and other megafauna. This cosmic event, linked to the onset of the Younger Dryas cooling period, may also explain the sudden disappearance of the Clovis culture across North America. The findings, published in PLOS One, highlight extreme heat and pressure signatures inconsistent with volcanic or human causes.
Nearly 13,000 years ago, at the end of the last ice age, a fragmented comet is believed to have exploded in Earth's atmosphere, unleashing widespread devastation. Researchers, led by UC Santa Barbara Emeritus Professor James Kennett, examined three prominent Clovis archaeological sites: Murray Springs in Arizona, Blackwater Draw in New Mexico, and Arlington Canyon on California's Channel Islands. These locations are renowned for documenting the megafaunal extinctions and the abrupt end of the Clovis culture, characterized by distinctive stone tools.
The team identified shocked quartz grains in sediment layers—sand particles fractured and altered by intense heat and pressure. "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," Kennett explained. Using electron microscopy and cathodoluminescence, the scientists confirmed these changes exceeded conditions from volcanic activity or early human fires.
This discovery aligns with the Younger Dryas impact hypothesis, positing that comet fragments detonated as airbursts, generating shockwaves and immense heat without forming a crater, similar to the 1908 Tunguska event. "In other words, all hell broke loose," Kennett said. The explosions likely ignited massive fires, producing a carbon-rich "black mat" layer observed across North America and Europe, while smoke and dust blocked sunlight, causing an "impact winter." Rapid ice sheet melting further cooled the climate, lasting about 1,000 years and interrupting post-glacial warming.
Supporting evidence includes elevated levels of comet-associated elements like platinum and iridium, nanodiamonds, metallic spherules, and meltglass in the same layers. Hydrocode modeling simulated these low-altitude blasts, reproducing the varied shock patterns in the quartz, from highly to lowly shocked grains. "There are going to be some very highly shocked grains and some that will be low-shocked. That's what you would expect," Kennett noted.
Collectively, these indicators suggest the cosmic impact was a major factor in the loss of large Ice Age animals, such as mammoths and mastodons, and the collapse of human populations from Alaska to South America. The study, published in PLOS One on September 2025 (DOI: 10.1371/journal.pone.0319840), builds on two decades of research into this prehistoric catastrophe.