New research challenging the Younger Dryas Impact Hypothesis argues that volcanic activity, rather than a comet impact, likely caused the final cold spell of the last ice age, based on recent sediment analysis.
Texas A&M researchers revealed their new findings in a recent paper published in Science Advances, adding growing evidence for the true cause of the extinction-level event that killed off North America’s mammoths and mastodons. The new work provides fresh evidence for the volcanic explanation of Earth’s most recent near-glaciation, as well as counterpoints to the Younger Dryas Impact Hypothesis.
The Younger Dryas
Over a 1,200-year period from around 12,900 to 11,700 years ago, the Earth’s Northern Hemisphere experienced a dramatic and catastrophic cooling. While this period represents the end of the last ice age, it is notable for producing one final period of extreme cold. During this period, the Atlantic Meridional Overturning Circulation system, which circulates heat around the globe, was disrupted, leading to a near-glacial Northern Hemisphere.
While the Younger Dryas Impact Hypothesis proposes that an extraterrestrial impact caused this climate catastrophe, this idea is not widely accepted among scientists. The Texas A&M team went into their work highly skeptical of the impact theory, expressing there was limited support for the idea, but curious about the heavily debated cause of this cooling period.
Younger Dryas Sediment
For their recent study, the Texas A&M team investigated North American continuous sedimentary records in Texas and Florida, quantifying the sediments’ osmium isotopic and highly siderophile element (HSE) ratios. The PL site in Florida, which provided some of the samples, is one of America’s best-dated geological sites, ensuring the accuracy of the sample dating. The team’s analysis showed that the data matched expectations for volcanic aerosol deposition.
They then compared these results to Antarctic and Greenland ice core data, finding a correlation between the observed North America isotope patterns and significant volcanic activity that occurred between 12,980 and 12,870 years ago. The Texas A&M team says that their findings constitute an unambiguous signal in a broad stream of data sources pointing toward a volcanic explanation for the Younger Dryas.
While some Younger Dryas Impact Hypothesis proponents regard the presence of unradiogenic osmium isotopes in the sediment as evidence for an extraterrestrial impact, the Texas A&M team points out that these isotopes can also be produced by volcanic activity, hydrothermal fluxes, or the weathering of basaltic rocks.
Osmium isotope ratios from sediment samples from the PL site were consistent with volcanic activity rather than space rock debris, and this finding was consistent with data from other North American sites, the researchers say. The team argues that extraterrestrial impacts are unreasonably unlikely to produce continent-wide geochemical anomalies, as seen in the North American sediment, and would require an implausible number of impacts in a short period, compared to the more likely explanation of a period of high volcanic activity.
Addressing The Younger Dryas Impact Hypothesis
Beyond their sediment analysis, the researchers also addressed other elements of the impact hypothesis in the paper. While space impacts are rare and no craters have been identified as related to the Younger Dryas, the team notes that reduced surface pressure during deglaciation, as would occur as Earth emerged from the Ice Age, can increase magma production, driving an increase in volcanic activity, making this explanation the most likely fit.
The researchers also raise an issue with a platinum anomaly that is frequently cited as evidence by those supporting the impact idea, who claim the platinum was likely delivered by the extinction-causing impact. In their rebuttal, the Texas A&M team notes that platinum spikes in the sediment actually slightly predate the Younger Dryas, suggesting the events are likely unrelated.
Notably, the paper states that their findings do not explain the duration of the Younger Dryas, only that volcanic activity acted as a trigger. Although the new work doesn’t offer a conclusive end to the debate, it adds greatly to the weight of evidence for a volcanic trigger of the Younger Dryas.
The paper, “Volcanic Forcing of Global Climate Cooling at the Younger Dryas Onset Preserved in North American Sediments,” appeared in Science Advances on April 29, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.