Massive eruptions roughly 719 million years ago in what is now Canada may have sucked enough CO2 from the atmosphere to freeze Earth over 2 million years later.
Devastating volcanic eruptions may have been so enormous they turned the planet into “Snowball Earth” 717 million years ago, according to the study.
The volcanic explosion – one of the largest in Earth’s history – likely triggered a series of chemical reactions that sucked carbon dioxide from the Earht’s ancient atmosphere.
The massive outburst, which occurred in what is now northern Canada, spewed cascades of lava that hardened into a volcanic highland covering 2.23 million square kilometers – an area three times the size of Texas. Acidic rain then fell on these fresh rocks, producing a chemical reaction that may have coved the planet in ice for 57 million years.
Experts already suspected that volcanic activity may have caused this glaciation episode, known as Sturtian glaciation. But they did not know exactly how the outburst caused the onset of Snowball Earth.
There are two main ways that volcanic eruptions can cool the planet down, according to the new study. Volcanic outbursts release gases containing sulfur-rich particles that become suspended in the atmosphere and block sunlight, resulting in cooling. Eruptions may also alter the climate through a chemical reaction known as weathering, which lava rocks are particularly susceptible to.
This weathering occurs when rainwater – which is slightly acidic due to dissolved carbon dioxide – reacts with the minerals in rocks to form clays and soluble salts. By forming these new minerals, CO2 is sucked out of the atmosphere and trapped in sediments that eventually wash into the ocean.
To better understand which mechanism triggered the Sturtian glaciation, the team needed to find exactly when the volcanic outburst took place. Sulfur particles remain suspended in the atmosphere for months to years, whereas rock weathering takes 1 million to 2 million years to spark a global cooling effect.
Their analysis suggests that the volcanic outburst took place 1 million to 2 million years before the glaciation, pointing to chemical weathering as the primary caue of Earth’s cooling.