Clovis spearpoints on display at the Cleveland Museum of Natural History in Cleveland, Ohio. Named for Clovis, New Mexico, where such uniquely designed spearpoints were first found by archeologists, these spearpoints date from 13,500 to 13,000 years ago. Photo Credit: Tim Evanson / CC 2.0
Recent research provides compelling new support for the theory that a fragmented comet exploded over Earth approximately 13,000 years ago, potentially triggering the widespread extinction of mammoths, mastodons, and other Ice Age megafauna, as well as the sudden disappearance of the Clovis culture, one of North America’s earliest known human technological traditions.
Published in PLOS One, the study was led by James Kennett, emeritus professor of Earth science and researcher at UC Santa Barbara’s Marine Science Institute, along with a team of collaborators. They report finding shocked quartz — grains of sand that have been physically transformed by exposure to extreme heat and pressure — at three important Clovis archaeological sites: Murray Springs in Arizona, Blackwater Draw in New Mexico, and Arlington Canyon on California’s Channel Islands.
These sites have long been central to our understanding of both megafaunal extinctions and the disappearance of the Clovis culture,” Kennett said.
The three classic Clovis archaeological sites in the study. Photo Credit: Courtesy Image
Their findings reinforce the Younger Dryas impact hypothesis, which links this extraterrestrial event to a sudden and severe climate shift known as the Younger Dryas. This period marked an abrupt return to near-glacial conditions lasting around a thousand years, interrupting the gradual warming trend at the end of the last Ice Age. The hypothesis proposes that the comet’s airburst caused massive wildfires, sending vast clouds of soot, dust, and smoke into the atmosphere. This debris likely blocked sunlight, triggering what is often described as an “impact winter,” which would have dramatically disrupted plant and animal life.
To confirm the presence of shocked quartz, the research team employed advanced techniques, including electron microscopy and cathodoluminescence. These analyses revealed distinctive microscopic fractures and traces of melted silica in the quartz grains—clear signatures of exposure to pressures and temperatures far exceeding those generated by volcanic activity or human influence.
The discovery of shocked quartz is particularly significant because the proposed cosmic event likely occurred as an “airburst” explosion in Earth’s atmosphere, similar to the 1908 Tunguska event in Siberia, which left no impact crater. Using hydrocode modeling, the researchers simulated how such low-altitude explosions could produce the range of shock patterns observed in the quartz grains.
“There are different levels of shock in the quartz grains,” Kennett explained. “Some grains show very intense deformation, while others are less affected. This variation fits with what we would expect from an airburst rather than a surface impact.”
This evidence, combined with other impact-related markers such as a distinctive carbon-rich “black mat” sediment layer, nanodiamonds, and metallic spherules found at these same archaeological sites, strengthens the case that a cosmic impact was a key factor contributing to the mass extinction of megafauna and the rapid decline of the Clovis culture at the onset of the Younger Dryas.
Adapted from original reporting by Sonia Fernandez, “Researchers find evidence of cosmic impact at classic Clovis archaeological sites,” The Current, UC Santa Barbara, 2025.