A recent study proposed compelling evidence supporting the theory that comet debris might have triggered the dramatic climate upheaval known as the Younger Dryas, around 13,000 years ago - an event that could have driven the extinction of North America's megafauna and marked the collapse of the Clovis culture. Universe Today reported that the Clovis culture, known for its distinctive spear point artifacts, vanished from the archaeological record around the same time the cold period began and as megafauna such as woolly mammoths and mastodons disappeared.
The study, published in PLOS One, suggested that a cosmic impact, possibly an airburst from a fragmented comet, may have caused the abrupt cooling that defined the period. Such impacts would have had massive environmental consequences, leading to widespread burning, as smoke and soot obscured the sun's rays, causing plummeting temperatures and ecological disaster in North America. Evidence included shocked quartz, small sand grains that have undergone deformation due to extreme heat and pressure, found at key archaeological sites tied to both the Clovis culture and megafaunal extinctions, such as Murray Springs in Arizona, Blackwater Draw in New Mexico, and Arlington Canyon in California's Channel Islands.
“These three sites were classic sites in the discovery and documentation of the megafaunal extinctions in North America and the disappearance of the Clovis culture,” said James Kennett, professor emeritus of earth sciences at the University of California, Santa Barbara. He succinctly described the catastrophic nature of the Younger Dryas event: “In other words, hell was unleashed,” according to Proceso.
Proponents of the Younger Dryas Impact Hypothesis, which posits that a cosmic impact abruptly chilled the Earth, have bolstered their argument with impact indicators, including microspherules, nanodiamonds, and minerals such as platinum and iridium - elements rare on Earth but typical in extraterrestrial objects like comets. The presence of shocked quartz is particularly significant; its formation is uniquely linked to high-pressure events that coincide with the hypothesis. The study's findings drew support through techniques like electron microscopy and cathodoluminescence, used to confirm the origins of the shocked quartz grains.
Moreover, features such as glass-filled fractures within the grains mirror those created by nuclear detonations and impacts in 27 recognized impact craters. This evidence connects these sites to cosmic events beyond terrestrial explanations.
However, the Younger Dryas Impact Hypothesis faces skepticism. Some researchers argue that alternate explanations could justify the findings associated with the impact hypothesis, such as the influx of freshwater into the North Atlantic. Critics also emphasize that the absence of an impact crater weakened the argument. Yet, proponents countered that the expected airburst impact would have left minimal direct evidence in the landscape, unlike the more dramatic Earth's surface scars left by asteroid impacts, such as the Chicxulub crater that ended the reign of the dinosaurs.
Researchers conducted hydrocode modeling to illustrate how such low-altitude explosions could create the shock patterns observed in quartz grains, supporting the notion that cosmic influences could explain the onset of the Younger Dryas.