Over 700 million years ago, Earth experienced one of its most extreme climate events, known as the Sturtian glaciation. During this time, ice sheets stretched from the poles to the equator, creating what scientists call a “Snowball Earth.”

Temperatures dropped so low they could freeze entire oceans, drastically reshaping the planet’s environment and its ability to support life.

For years, scientists have debated the causes behind this prolonged global freeze, but new research is beginning to uncover the forces responsible for triggering and maintaining it.

The Impact of Volcanic Carbon Dioxide Emissions

A team of geologists in Australia has recently published a study in Geology, pointing to a decline in volcanic carbon dioxide (CO2) emissions as a key factor in sparking this ice age.

Lead author Dr. Adriana Dutkiewicz, an ARC Future Fellow, explains: “Imagine Earth almost completely frozen over. That’s exactly what happened about 700 million years ago. However, the precise causes of the extreme cooling have remained uncertain—until now.”

To investigate, scientists turned to advanced plate tectonic models to track Earth’s shifting landmasses and volcanic activity.

Their research reveals that around 717 million years ago, CO2 emissions from mid-ocean ridges dropped to an all-time low.

Volcanic activity at these ridges typically releases CO2, a greenhouse gas that warms the planet. Its reduction caused Earth’s atmosphere to lose a key heat-trapping component, leading to a significant temperature drop and triggering global glaciation.

The Supercontinent Factor

Another key contributor to the deep freeze was the breakup of Rodinia, an ancient supercontinent. As tectonic plates shifted and fractured, fresh rock was exposed to the atmosphere, speeding up silicate weathering.

The chemical reaction removes CO2 from the atmosphere by binding it into minerals, further lowering greenhouse gas levels and amplifying the cooling trend.

A major factor in this process was the Franklin large igneous province (LIP), a vast volcanic region that now lies in Canada. The rapid weathering of rocks here significantly cut atmospheric CO2, leading to long-term cooling.

While earlier studies suggested volcanic eruptions could also cool the planet by releasing sulfur aerosols that reflect sunlight, this new research points to the long-term reduction in CO2 emissions as the primary driver of the ice age.

Why the Ice Age Lasted So Long

One of the most puzzling aspects of the Sturtian glaciation is its astonishing length. While most ice ages last just a few million years, this one lasted a remarkable 57 million years, from 717 to 660 million years ago.

Researchers suggest that the combination of reduced volcanic CO2 emissions and extensive silicate weathering created a feedback loop that kept Earth trapped in a frozen state.

Numerical models support this theory, showing that once CO2 levels dropped below 200 parts per million (ppm)—less than half of today’s levels—a runaway ice-albedo effect kicked in. As ice expanded, it reflected more sunlight, leading to further cooling and prolonging the ice age.

The freeze ended when volcanic activity picked up 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 climate.

Implications for the Future

This study offers valuable insights not just into Earth’s past but also its potential future. Dr. Dutkiewicz highlights that “Earth is currently on a trajectory of lower volcanic CO2 emissions, as continental collisions increase and tectonic plate movement slows down.”

Though this could suggest the possibility of another prolonged ice age far in the future, researchers stress that the timescales involved are vastly different from the rapid climate shifts caused by human activity today.

According to NASA and other climate organizations, while geological processes influence Earth’s climate over millions of years, human-driven CO2 emissions are causing changes at an unprecedented pace.

The burning of fossil fuels is increasing atmospheric CO2 far faster than natural geological processes can remove it, effectively counteracting any long-term cooling trends linked to plate tectonics.

By studying Earth’s climate history, scientists can better predict how both natural forces and human actions will shape the planet’s future.

The Sturtian glaciation serves as a powerful reminder that climate change is influenced by a complex mix of long-term geological forces and rapid human impact.

As research advances, scientists will continue refining their models to better understand these interactions and their implications for our world today.