Did an exploding comet wipe out the mammoths?
Scientists are uncovering new clues that a cosmic explosion may have rocked Earth at the end of the last ice age. At major Clovis-era sites, researchers found shocked quartz—evidence of intense heat and pressure consistent with a comet airburst rather than volcanism or human activity. The event could have sparked massive fires, blocked sunlight, and triggered a rapid return to ice-age conditions. These harsh changes may explain the sudden loss of megafauna and the disappearance of the Clovis culture.
Scientists are continuing to strengthen the case that a fragmented comet exploded in Earth's atmosphere nearly 13,000 years ago. This event may have played a role in the sudden disappearance of mammoths, mastodons, and many other large Ice Age animals, as well as the abrupt loss 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 colleagues describe new evidence found at three well-known Clovis archaeological sites. These sites include Murray Springs in Arizona, Blackwater Draw in New Mexico, and Arlington Canyon in California's Channel Islands. At each location, the team identified shocked quartz -- grains of sand that have been physically altered by extreme 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," said Kennett.
Linking Extinctions to the Younger Dryas
The loss of Ice Age megafauna and the disappearance of Clovis tools and artifacts occurred around the same time as the onset of the Younger Dryas. This period marked a sudden and unusual return to near ice-age conditions that lasted roughly a thousand years, interrupting an overall warming trend following the Last Glacial Period.
Several explanations have been proposed for what triggered this dramatic climate reversal. Kennett and his team support the Younger Dryas impact hypothesis, which suggests that fragments of a comet detonated above Earth's surface. These explosions would have released immense heat and powerful shockwaves across large regions.
"In other words, all hell broke loose," Kennett said. Under this hypothesis, the blasts ignited widespread fires that filled the atmosphere with smoke, soot, and dust. This debris likely blocked sunlight and produced an "impact winter." At the same time, rapid melting of ice sheets may have contributed to further cooling in affected areas. Together, the immediate destruction and the harsh environmental aftermath could have pushed many large animals to extinction and disrupted human populations across North and South America.
Growing Evidence for a Cosmic Impact
Over the past two decades, researchers supporting this idea have gathered multiple lines of evidence. One of the most widespread findings is a dark, carbon-rich "black mat" layer found in sediment across many sites in North America and Europe, which points to extensive burning.
Scientists have also identified a range of impact proxies. These include elevated levels of rare elements commonly associated with comets, such as platinum and iridium. Other indicators include materials formed only under extreme heat and pressure, including nanodiamonds, metallic spherules, and meltglass created when minerals melted and then rapidly cooled.