Around 700 million years ago, Earth was a very different planet—gripped by extreme deep freezes during the Cryogenian period. Enormous glaciers, kilometers thick, stretched across vast regions, turning much of the planet into a frozen wasteland.

However, new research suggests that these massive glaciers could have played a crucial role in fostering the evolution of complex life on Earth by depositing essential nutrients into the oceans as they melted.

Was Earth Once a Snowball?

The Snowball Earth hypothesis suggests that Earth experienced at least two global glaciations during the Cryogenian period. During these events, ice sheets expanded across the planet, reaching from the poles to the equator.

This concept is supported by evidence found in sedimentary rocks formed under glacial conditions, showing that glaciers reached extreme latitudes. Though the cause of these deep freezes remains unclear, scientists believe a significant drop in atmospheric carbon dioxide—possibly driven by tropical weathering—could have played a major role.

Glaciers As Cosmic Bulldozers

While glaciers are often seen as destructive forces, their role during the Cryogenian was more complex. Acting as enormous bulldozers, glaciers ground down Earth’s rocky surface, breaking it into finer particles.

These particles, previously trapped beneath the ice, were released when the glaciers finally retreated. Once the minerals washed into the oceans, they provided essential nutrients that could have been key to supporting the evolution of more complex life forms beyond simple microorganisms.

The Role Of Volcanic Activity In Ending The Ice Age

Although glaciers dominated Earth’s climate during the Snowball Earth period, volcanic activity may have been a decisive factor in ending these extreme ice ages. As ice sheets advanced, the interactions between Earth’s crust, oceans, and atmosphere slowed, trapping carbon dioxide in the atmosphere.

Eventually, volcanic eruptions began releasing large amounts of CO2, causing the gas to accumulate in the atmosphere. This buildup led to a runaway greenhouse effect that gradually warmed the planet, melting the ice and shifting the climate. The ensuing thaw marked a dramatic transition in Earth’s climate and oceans.

Glaciers And The Emergence Of Complex Life

The melting of glaciers had a profound impact on Earth’s oceans, introducing vast quantities of nutrients that altered their chemistry. This nutrient influx likely set off a series of biological changes, creating favorable conditions for the rise of more complex organisms.

The rapid changes in the ocean’s chemistry and nutrient availability may have been instrumental in supporting the emergence of multicellular life, paving the way for the diverse range of organisms we see today.

Glacial Retreat: A Planetary Power Hose

New research underscores the idea that the retreat of glaciers played an equally significant role as volcanic activity in driving biological evolution. By studying ancient rock layers from the Snowball Earth period, scientists identified distinct changes in the Earth’s crust that coincided with both the advance and retreat of glaciers.

Once the glaciers began to melt, massive outflows of meltwater transported minerals trapped beneath the ice. These minerals, upon reaching the oceans, dissolved and released vital chemicals, reshaping oceanic chemistry and fostering conditions necessary for the development of life.

Such changes in the distribution of essential elements in the ocean proved crucial to the thriving ecosystems that followed the Snowball Earth period. With access to these newly available nutrients, life found the foundation it needed for further biological advancements.