The destructive forces that gave rise to complex life on Earth were hidden within ancient glaciers.

The history of Earth spans over 4.5 billion years, during which our planet has become home to an astonishing array of species: some have long since gone extinct, while others continue to thrive. However, the mystery of how complex life first originated on Earth remains unsolved. Now, it appears that scientists have uncovered the devastating forces that spurred the emergence of complex life on our planet, according to Science Alert.

Approximately 700 million years ago, during the Cryogenian period, our planet looked vastly different. During this chapter of its history, Earth plunged into a series of profound freezes, with enormous glaciers flowing across the globe.

In a new study, researchers demonstrated that these immense rivers of ice encircling the planet sometimes reached incredible depths of kilometers and ground the rocky surface of the Earth like gigantic bulldozers. When the ice eventually melted, the crushed minerals were washed into the oceans, where they could provide the nutrients necessary for the development of complex life.

According to the widely accepted snowball Earth theory, our planet underwent at least two extreme glaciations during the Cryogenian. Evidence of these events can be observed worldwide in sedimentary rocks formed under glacial conditions. This compellingly indicates that ice during that period spread from the poles to reach the equatorial regions.

Scientists still do not know what specifically triggered such deep freeze events, but several possible scenarios have been proposed. One hypothesis suggests a significant drop in greenhouse gases in the Earth's atmosphere, particularly carbon dioxide.

It is thought that the level of carbon dioxide in Earth's atmosphere may have decreased due to increased weathering of rocks located on a large tropical continent that existed at the time. When continents are situated in tropical regions, warm, moist conditions accelerate chemical weathering, pulling CO2 from the atmosphere and locking it in carbonate minerals.

It is also believed that tectonic activity, leading to the breakup of the supercontinent during that period, may have played a role. This could have created conditions such as shallow seas, resulting in greater removal of CO2 from the air. Ice sheets gradually advanced toward the tropics, reflecting more sunlight back into space, which led to further cooling of the planet.

It is unknown how exactly the snowball Earth period came to an end, but scientists believe it may have been preceded by volcanic activity that played a key role in terminating the glacial periods. When glaciers covered the planet, the interaction between the Earth's crust, oceans, and atmosphere slowed dramatically. As a result, when volcanoes erupted, releasing CO2 into the atmosphere, it was not reabsorbed but rather accumulated over millions of years.

The result of these elevated CO2 levels led to a greenhouse effect, warming the planet, and ultimately melting the ice. The subsequent melting triggered a rapid rise in sea levels and a surge of nutrients into the oceans. Scientists believe that this influx of nutrients likely set the stage for the emergence of complex life on Earth.

Previously, researchers had considered the idea that changes in atmospheric conditions during the melting of snowball Earth altered ocean chemistry. But now, scientists have discovered that the material scraped off the continents during melting may have also played a significant role.

According to co-author of the study, Professor Chris Kirkland from Curtin University, he and his colleagues examined rock samples from older to younger. As a result, they were able to create a picture of what glaciers and the subsequent river systems did to the planet's crust.

The scientists studied minerals from these sequences of rock and identified consistent distinctive changes during the periods when snowball events began, as well as when melting occurred. As glaciers retreated during melting periods, massive flows of meltwater carried mineral grains that had been captured and stabilized beneath the ice. Upon contact with liquid water, fragile minerals dissolved, releasing chemicals. It is believed that this process may have ultimately sparked the development of more complex life on Earth.