During the Neoproterozoic Era (1 billion to 538.8 million years ago), Earth underwent dramatic climate fluctuations, notably the Sturtian Ice Age, where ice is believed to have enveloped the planet. Understanding the geological record and the survival of life during this pivotal event has remained a significant challenge. Geochronological studies indicate that the Sturtian Ice Age persisted for an astonishing 56 million years, far exceeding predictions made by conventional climate models. A recent study from Harvard University proposes that Earth may have experienced cycles of ice-covered and ice-free states during the Sturtian period.

“The global glaciation that occurred near the advent of animal life, known as the Neoproterozoic Snowball Earth event, represents one of the most severe climate transformations in Earth’s history and likely had profound effects on biological evolution,” stated Charlotte Minsky, a Harvard graduate student, along with her research team.

“However, the causes, severity, and ecological impacts of these glaciations continue to be the subject of intense debate.”

Employing a coupled model of ancient climate systems and the global carbon cycle, researchers propose that Earth was not trapped in a singular, incessant snowball state.

Their simulations indicate that extensive weathering of basalt in the Franklin Igneous Province, a significant volcanic area in northern Canada that likely erupted prior to the Sturtian Ice Age, dramatically reduced atmospheric carbon dioxide levels, leading to multiple global ice ages.

As volcanic activity and other processes gradually rebuilt atmospheric carbon dioxide, global temperatures rose, ice melted, and previously covered basalt regions were exposed once more.

This renewed decomposition through weathering replenished carbon dioxide, triggering another snowball cycle.

The authors contend that this recurring cycle of freezing and thawing driven by carbon dioxide could sustain glacial and interglacial variations for tens of millions of years.

The mechanisms revealed in this study address several longstanding discrepancies, particularly the duration of the Sturtian Ice Age, which was previously challenging to reconcile with established climate models.

This research aligns with sedimentation patterns from that era, elucidating how atmospheric oxygen levels could remain stable amidst extreme climatic shifts.

Moreover, frequent returns to warmer, ice-free states may have been critical in preventing a total collapse of atmospheric oxygen.

“This discovery may elucidate how aerobic life continued to thrive throughout such severe intervals,” Minsky noted.

For more details, refer to the study published in Proceedings of the National Academy of Sciences.

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Charlotte Minsky et al. 2026. The snowball greenhouse cycle repeats within Neoproterozoic Sturtian glaciers. PNAS 123 (19): e2525919123; doi: 10.1073/pnas.2525919123