Not a comet: volcanoes may have triggered the sudden freeze 12,900 years ago that helped wipe out America’s mammoths

About 12,900 years ago, the climate across the Northern Hemisphere flipped. Temperatures fell by up to 10 degrees Celsius, almost 20 degrees Fahrenheit, within a single human lifetime, and a cold spell called the Younger Dryas settled in for more than 1,000 years. Mammoths, along with most of America’s other large Ice Age animals, died out around that time. For years, one popular explanation blamed a comet or asteroid. A team at Texas A&M University now says the evidence points somewhere else: to a cluster of major volcanic eruptions.

A site beneath Florida’s Aucilla River

The work centers on Page-Ladson, a site on the Aucilla River about 40 minutes outside Tallahassee, Florida. A recreational diver named Buddy Page found it in the late 1970s. It lies about 6 miles from the coast, under roughly 30 feet of water, and its sediment column holds almost 20 feet of artifacts and fossils that date from 8,000 to 18,000 years ago.

Archaeologists Michael Waters and Jessi Halligan reinvestigated Page-Ladson starting in 2012. They found nothing at first, but in 2013 they pulled out an unambiguous stone knife older than 14,000 years. The oldest artifact there now exceeds 15,200 years, and they published those earlier results in 2016. Their team has also identified a nanodiamond marker layer at the start of the Younger Dryas in sediment in both Florida and Texas, and that layer became the target of the new work.

The impact idea and its problem

The marker layer contains tiny diamonds and platinum-group elements, and researchers have used it as evidence that a comet or asteroid struck at the start of the Younger Dryas. Lucien Nana Yobo, an isotope geochemist in Texas A&M’s Department of Geology and Geophysics, decided to test the layer more closely. He weighed three explanations for the freeze: a freshwater flood into the North Atlantic, an impact, and volcanic eruptions.

His key tool was osmium, a platinum-group metal whose isotope ratios act like a fingerprint. Space rocks and Earth rocks carry different ratios. The samples matched terrestrial values, and they showed a single isotopic fingerprint that also appears at three North American locations. That result points toward a volcanic event and away from an extraterrestrial one. Nana Yobo builds on earlier ice-core research from Greenland and Antarctica.

Collecting mud without contaminating it

The sampling itself took careful work. Divers needed clean mud from the exact moment of the freeze, and metal tools would have contaminated platinum-group measurements. The team collected sediment using cut vinyl gutters and nonmetallic fishing line instead of metal tools.

How eruptions could freeze a hemisphere

Nana Yobo says the evidence “points to a cluster of major eruptions.” Volcanic aerosols probably caused the first, short-lived cooling, and feedbacks involving sea ice and ocean circulation could then have stretched the cold across more than a thousand years. The cooling likely sped up the extinction of most American megafauna, which already faced pressure as glaciers melted and the ocean rose about 100 meters.

What nobody knows yet

The team cannot yet say which volcanoes erupted, where they sit, or how much material they ejected. The proposed volcanoes sit on the other side of the planet from the site. Future work may analyze cryptotephra, microscopic volcanic glass, to trace the sources, though nobody has done that for these sites yet. Part of Nana Yobo’s work received funding from a Texas A&M College of Arts and Sciences merger grant. The university announced the results in a news release on 27 October 2026 and did not name a journal paper, so the details above rest on the researchers’ own account until the study appears in print.

Sources: Texas A&M University College of Arts and Sciences news release “Deep in the Floridian Mud, Evidence of an Ancient Disaster” (Kevin Matyi, 27 October 2026). No journal paper or DOI is named. Lead image: mammoths on a grassy prairie, Jessi Halligan, as supplied with the release.