The key facts

  • A study of Page-Ladson sediments (Florida) points to volcanic activity rather than a cosmic impact
  • Osmium and rhenium isotopes are closer to volcanic aerosols than to meteoritic material
  • A team from the University of Maine relies on Greenland samples showing signs of impact

Two Versions of the Same Cooling

The Younger Dryas is a cold period that began at the end of the last glaciation. One hypothesis about its causes suggests that Earth may have been struck by a comet or its fragments at that time. In 2026, two studies were published offering different explanations for the event.

Florida Sediments Point to Volcanoes

A team led by Lucien Nana Yobo studied bottom sediments from the underwater archaeological site of Page-Ladson in Florida; the results were published in the journal Science Advances. The site preserves well-dated continuous sediment layers spanning the beginning of the Younger Dryas. The scientists examined osmium isotope ratios, as well as the content of rhenium and other elements that help determine the origin of the material. In the layers corresponding to the onset of the cooling, the isotopic composition of osmium changed, and the amounts of osmium and rhenium increased. However, the element ratios better match volcanic aerosols — fine particles ejected into the atmosphere during eruptions — than meteoritic material. In the authors' view, the chemical signatures are more reliably explained by products of volcanic eruptions rather than by material of cosmic origin.

Conclusions and Interpretation of the Team

Texas A&M University reported the results on August 10, noting that the team also compared the data with independent data from other regions. According to the researchers' interpretation, several large eruptions over a short period could have disrupted the circulation of Atlantic Ocean waters and triggered climate changes. 'Our study provides robust geochemical evidence that the key role was played not by a cosmic impact but by volcanic activity,' said lead author Lucien Nana Yobo.

The Alternative Position: Impact Traces in Greenland

Proponents of the cosmic impact hypothesis rely on samples from Greenland. The Climate Change Institute of the University of Maine reported on June 1 on the work of James Kennett, Paul Mayewski, Andrei Kurbatov and co-authors. They studied ice layers at the edge of the ice sheet in the Kangerlussuaq area. In a dust-rich dark layer, they described quartz with microstructures characteristic of impacts, melted and re-solidified glass, small spherical particles, carbonaceous particles, as well as nanoparticles enriched in certain metals, including platinum-group elements. Thus, the two 2026 studies adhere to opposing explanations for the causes of the Younger Dryas.