Earth researchers, led by pioneering paleoclimatologist James Kennett, have found a fascinating smoking gun. They discovered strong signs of a cosmic impact at three major Clovis culture archaeological sites across North America. Together, the discoveries lend credence to the Younger Dryas impact hypothesis. They argue that the impact of such a space rock was responsible not only for the rapid extinction of megafauna but for the abrupt collapse of the advanced Clovis culture, about 12,900 years ago. The study’s findings were recently released in a joint paper in PLOS One.
Kennett and his team took a look at 10 different sites. Their field sites included Murray Springs in Arizona, Blackwater Draw in New Mexico, and Arlington Canyon located on California’s Channel Islands. At every site, the findings were shocking. This clues us in on a huge prehistoric cosmic event that was possibly one of the dramatic forces that changed habitats and ecosystems during the late Pleistocene epoch.
Discovery of Shocked Quartz
At these archaeological sites, researchers found shocked quartz. This mineral can be altered unequivocally by the intense pressures and heats typically associated with cosmic impacts. This piece of quartz, mineralized with calcite, displays beautiful hackly fractures. Many of them are partially or entirely filled with melted silica, testifying to the hellish conditions of the impact event. Description of shocked quartz, an essential marker for a high-energy impact.
In addition to shocked quartz, the team found an entire suite of impact proxies. The crater floor was strewn with unnaturally high concentrations of some rare minerals, including platinum and iridium. These features are typically attributed to non-terrestrial origins and even more strengthen the theory that some sort of cosmic event took place. Other proxies found include nanodiamonds, metallic spherules and meltglass — more evidence for an impact.
Kennett’s group additionally reported a “black mat” layer within the sediment at most sites in North America and Europe where they found evidence for this cosmic impact. On this layer, signs of extensive burning are very apparent. It helps make the case that a cataclysmic event led to drastic environmental shifts.
The Younger Dryas Impact Hypothesis
The Younger Dryas impact hypothesis proposes that explosions from cosmic objects caused widespread devastation, including burning and smoke that blocked sunlight. This phenomenon could have led to an asteroid-induced “impact winter.” In part, that’s because temperatures dropped — and climate patterns changed drastically. Such conditions would have been extremely harmful to all plant and animal life, even triggering mass extinctions.
These conditions were in place just as a wave of megafauna started to go extinct. Mammoths and mastodons, iconic beasts of the North American tundra, disappeared in droves at this time. This is when we start to see a decline of the Clovis technocomplex—evidence of highly advanced stone tool technology and large mammal hunting practices. This suggests a connection between the impact event and the significant shifts in biodiversity and human culture during the Younger Dryas cool episode.
Kennett suggests an exciting alternative, that a disintegrating comet blew up in the sky. This blast released shockwaves and incredible heat, instantly creating firestorms that forever changed habitats over thousands of miles. The start of the Younger Dryas also marked a sudden reversion to ice-age conditions, lasting for a full millennium. This dramatic change brought with it severe ecological changes.
Implications for Archaeology and Prehistoric Life
The importance of this research extends beyond archaeological curiosity. It flips our accepted story about how humans and animals made it through this wild and whirly time. The finding of these impact proxies and shocked quartz at Clovis sites raises interesting questions. How were these populations able to cope with, or not cope with, such rapid environmental changes?
In the meantime, researchers are investigating these findings. In doing so, their works can illuminate the wider effects that cosmic occurrences like these have had on our planet’s history. Reconstructing what this event did to drive ecological changes will help us better understand what life was like on prehistoric Earth. Beyond that, it enables us to address some of today’s most pressing environmental issues.