Earth’s climate has undergone dramatic swings over its long history, but few events were as extreme as the periods when the planet nearly froze over entirely.
During these episodes, known as Snowball Earth, ice sheets spread from the poles toward the equator, turning much of the planet into a frozen world.
Now, a new study led by researchers at the Earth-Life Science Institute at Institute of Science Tokyo has uncovered fresh clues about what kept Earth locked in these deep freezes for millions of years.
Using advanced numerical geochemical models, scientists found that chemical reactions between water and rock may have continued beneath massive ice sheets, something previously thought unlikely.
These reactions, known as chemical weathering, can remove carbon dioxide (CO2) from the atmosphere. According to the study, this process may have continued under thick glaciers during ancient ice ages, potentially slowing the warming needed to melt the ice and prolonging the frozen conditions.
“Subglacial weathering represents a previously unrecognised feedback mechanism that could explain the very different durations of snowball Earth events,” said lead author Shintaro Kadoya.
The research focuses on two major global glaciations that occurred during the Neoproterozoic Era, the Sturtian glaciation and the Marinoan glaciation. Geological evidence shows that the Sturtian event lasted four to fifteen times longer than the Marinoan glaciation, despite occurring under broadly similar conditions. Until now, scientists have struggled to explain this striking difference.
Traditionally, researchers believed that chemical weathering would have stopped during global glaciations because continents were buried under ice and lacked liquid water. Without weathering, removing CO2 from the atmosphere, volcanic emissions would slowly accumulate greenhouse gases until warming became strong enough to melt the ice.
However, the new modelling suggests a different scenario. Beneath thick ice sheets, geothermal heat from Earth’s interior could melt ice at the base of glaciers, producing liquid water.
This meltwater may flow through crushed rock created by glacial erosion, allowing chemical reactions to continue even while the planet’s surface remained frozen.
The simulations show that under such conditions, subglacial weathering could consume substantial amounts of atmospheric CO—sometimes nearly matching the amount released by volcanoes. If true, this hidden process could have delayed global warming and extended the duration of snowball Earth states.
The findings also suggest that differences in meltwater supply and erosion beneath glaciers could explain why some glaciations lasted far longer than others.
Researchers say these subglacial reactions may also have influenced ocean chemistry by delivering nutrients such as phosphorus into the seas once the ice began melting.
Together, the study reveals that the frozen landscapes of ancient Earth may have been far more chemically active than previously believed, playing a key role in shaping the planet’s most extreme climate episodes.
