Study Says Earth Thawed and Refroze for 56 Million Years During Sturtian Snowball
Updated
Updated · ZME Science · May 13
Study Says Earth Thawed and Refroze for 56 Million Years During Sturtian Snowball
6 articles · Updated · ZME Science · May 13
A new PNAS study argues the Sturtian glaciation, from about 717 million to 660 million years ago, was not one continuous deep freeze but a repeating thaw-refreeze cycle.
The model ties that 56-million-year span to basalt from northern Canada’s Franklin Large Igneous Province: fresh volcanic rock drew down CO2, cooling Earth, while ice later slowed weathering and let volcanic CO2 rebuild until warming returned.
That loop could reconcile conflicting rock evidence that shows both low-latitude glaciers and intervals of open water, a mismatch that standard hard-Snowball and slushy-Snowball models struggle to explain.
The stop-start freeze also offers a survival route for oxygen-using microbes, which may have endured a series of harsh freezes broken by warmer windows rather than one uninterrupted global ice age.
Researchers say similar carbon-cycle swings could matter beyond Earth, suggesting some frozen rocky exoplanets may alternate between ice and warmth instead of remaining permanently dead worlds.
A volcanic feedback loop caused a 56-million-year ice age. What prevents a similar climate catastrophe from occurring today?
Basalt weathering drove Earth's longest ice age. What other geological triggers could dramatically reshape a planet's climate?
If Earth's 'Snowball' phase was a cycle of freezing and thawing, could frozen exoplanets be hiding undiscovered life?
56 Million Years of Climate Oscillations: How Cyclical Snowball Earth Events Reshaped Early Evolution and Exoplanet Insights
Overview
Recent research led by Harvard University has overturned the traditional view that the Neoproterozoic Snowball Earth was a single, uninterrupted global freeze. Instead, the study reveals that during the Sturtian glaciation, Earth's climate cycled between fully ice-covered 'snowball' states and warm, ice-free 'hothouse' periods. This dynamic climate was driven by interactions between volcanic activity, weathering of exposed basalt, and changes in atmospheric CO₂. These findings not only reshape our understanding of ancient climate and its impact on early life, but also suggest that similar cycles could occur on other rocky planets with active carbon cycles.