Earth experienced extreme climate swings during the Neoproterozoic epoch (one billion to 538.8 million years ago), including the Sturtian glaciation, when ice likely covered the planet. Explaining aspects of the geologic record and the survival of life through this event has been a longstanding puzzle. Additionally, geochronology indicates that the Sturtian glaciation lasted for 56 million years — far longer than standard climate models have predicted. New research from Harvard University suggests that Earth may have alternated between ice-covered and ice-free states for the duration of the Sturtian.
An artist’s impression of the ‘Snowball Earth.’ Image credit: Oleg Kuznetsov, http://3depix.com / CC BY-SA 4.0.
“Global glaciations near the dawn of animal life — the so-called Neoproterozoic Snowball Earth events — are among the most extreme climatic perturbations in Earth’s history and likely exerted a strong influence on biological evolution,” said Harvard University graduate student Charlotte Minsky and her colleagues.
“Nonetheless, the cause(s), severity, and environmental/biological effects of these glaciations are still vigorously debated.”
Using a coupled model of the ancient climate and the global carbon cycle, the researchers make the case that Earth may not have been locked in a single, unbroken Snowball Earth state.
Their simulations suggest that intense weathering of basalt in the Franklin Large Igneous Province, a vast volcanic region located in northern Canada and believed to have erupted just before the onset of the Sturtian glaciation, drew down atmospheric carbon dioxide enough to trigger multiple global glaciations.
As volcanoes and other processes slowly rebuilt atmospheric carbon dioxide, the climate warmed, the ice retreated, and large areas of fresh basalt were again exposed to the atmosphere.
Renewed breakdown from weathering then pulled carbon dioxide back down, pushing the climate into another Snowball phase.
This repeating cycle of carbon dioxide-driven freezing and thawing, the authors argue, could naturally sustain glacial-interglacial swings over tens of millions of years.
The mechanisms revealed by the study resolve several longstanding paradoxes, most notably the previously inexplicable length of the Sturtian when compared with physical climate models.
The study also matches observed sedimentary patterns from that time period and explains how atmospheric oxygen levels could have remained stable despite extreme climate upheavals.
Repeated returns to warmer, ice-free conditions may have helped prevent a complete collapse of atmospheric oxygen, the study further suggests.
“This could help explain how aerobic life persisted through such an extreme interval,” Minsky said.
The study was published in the Proceedings of the National Academy of Sciences.
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Charlotte Minsky et al. 2026. Repeated snowball-hothouse cycles within the Neoproterozoic Sturtian glaciation. PNAS 123 (19): e2525919123; doi: 10.1073/pnas.2525919123
