Over 700 million years ago, Earth underwent one of its most extreme climate events, known as the Sturtian glaciation. During this period, ice sheets covered the entire planet from pole to equator, creating what scientists refer to as a “Snowball Earth.” Temperatures plummeted to levels capable of freezing entire oceans, dramatically altering the planet’s environment and its potential for life.
Scientists have long debated what caused this prolonged global freeze, but new research is shedding light on the forces that triggered and sustained it.
The Role of Volcanic Carbon Dioxide Emissions
A team of geologists in Australia recently published a study in the journal Geology, revealing that a decline in volcanic carbon dioxide (CO2) emissions played a crucial role in initiating this ice age.
Lead author Dr. Adriana Dutkiewicz, an ARC Future Fellow, describes the event: “Imagine Earth almost completely frozen over. That’s just what happened about 700 million years ago. However, the exact causes of this extreme cooling have remained uncertain—until now.”
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To investigate, scientists used advanced plate tectonic models to trace Earth’s landmasses and volcanic activity. Their findings indicate that around 717 million years ago, CO2 emissions from mid-ocean ridges fell to a historic low. Since volcanic activity at these ridges normally releases significant amounts of CO2, a greenhouse gas responsible for warming the planet, this reduction meant Earth’s atmosphere lost a critical heat-trapping component. As a result, temperatures plunged, setting the stage for global glaciation.
The Supercontinent Connection
Another factor contributing to this deep freeze was the breakup of Rodinia, an ancient supercontinent. As tectonic plates shifted and fractured, fresh rock was exposed to the atmosphere, accelerating the process of silicate weathering. This chemical reaction removes CO2 from the atmosphere by binding it into minerals, further reducing greenhouse gas levels and reinforcing the cooling trend.
A key player in this process was the Franklin large igneous province (LIP), a massive volcanic region in what is now Canada. Rapid weathering of these rocks significantly reduced atmospheric CO2, leading to long-term cooling.
While previous studies suggested that volcanic eruptions could also contribute to cooling by releasing sulfur aerosols that reflect sunlight, this new research points to the long-term reduction in CO2 emissions as the dominant driver of the ice age.
Why the Ice Age Lasted So Long
One of the most puzzling aspects of the Sturtian glaciation is its extraordinary duration. While most ice ages in Earth’s history lasted a few million years, this one stretched from 717 to 660 million years ago—lasting an astonishing 57 million years.
Researchers propose that the combination of reduced volcanic CO2 emissions and extensive silicate weathering created a feedback loop that kept Earth locked in a frozen state. Numerical models support this hypothesis, showing that once CO2 levels dropped below 200 parts per million (ppm)—less than half of today’s levels—a runaway ice-albedo effect took hold. As ice expanded, it reflected more sunlight, causing further cooling and extending the ice age.
The freeze finally ended when volcanic activity increased again, releasing enough CO2 to warm the planet. Mid-ocean ridge activity and terrestrial volcanism gradually replenished atmospheric CO2, melting the ice sheets and returning Earth to a more temperate state.
Implications for the Future
This study provides crucial insights not only into Earth’s past but also its potential future. Dr. Dutkiewicz notes, “Earth is currently on a trajectory of lower volcanic CO2 emissions, as continental collisions increase and tectonic plate movement slows down.”
While this suggests that another prolonged ice age could occur in the distant future, researchers emphasize that the timescales involved are vastly different from the rapid climate changes caused by human activity today.
According to NASA and other climate organizations, geological processes influence Earth’s climate over millions of years, while human-induced CO2 emissions are driving change at an unprecedented rate. The burning of fossil fuels is increasing atmospheric CO2 far faster than natural geological processes can remove it, counteracting any long-term cooling trends associated with plate tectonics.
Understanding Earth’s climate history helps scientists predict how natural forces and human activities will shape the planet’s future. The Sturtian glaciation serves as a stark reminder that climate change is a complex system influenced by both long-term geological processes and rapid human intervention. As research continues, scientists will refine their models to better understand these interactions and their implications for the world we live in today.
