Scientists in Australia have figured out what most likely caused a period of extreme cold on Earth over 700 million years ago. By using models of how the continents move over time, they discovered low levels of the greenhouse gas carbon dioxide in the atmosphere were to blame.

This finding, published in the journal Geology, gives us a better idea of how Earth’s natural thermostat works to prevent temperatures from getting too high. It also shows climate is sensitive to how much carbon dioxide is in the air.

Lead researcher Dr. Adriana Dutkiewicz from the University of Adelaide explained it this way: Imagine the Earth was nearly frozen solid. We cracked the case – volcanic emissions of CO2 gas were unusually low due to weathering of old volcanic rocks in Canada absorbing CO2 from the sky.

The scientists were inspired to solve this mystery because rocks from that deep freeze can still clearly be seen in Australia’s Flinders Ranges mountains.

On a recent field trip there with colleague Professor Alan Collins, they used computer simulations to figure out why it was so cold for so long – a whopping 57 million years.

This extremely long ice age, nicknamed the Snowball Earth, occurred between 717 to 660 million years ago when dinosaurs and plants hadn’t evolved yet. As Dr. Dutkiewicz said, We wanted to know what triggered it and why it lasted so unusually long.

The team used plate tectonics models showing how continents drift over eons. They linked this to simulations of volcanic CO2 emissions at sea as the planet’s crust slowly spreads open. This revealed volcanic CO2 hit a record low exactly when the freezing began. CO2 levels remained modest throughout.

As there were no complex animals or plants at the time, CO2 amounts in the atmosphere mostly depended on volcanoes and rocks absorbing the gas, said Dr. Dutkiewicz. Professor Dietmar Müller from the University of Sydney added, Geology dominated – less volcanic CO2 plus rocks in Canada soaking it up pushed CO2 down, triggering deep freezing.

Their research raises thought-provoking questions about Earth’s deep future. While some predict recurring super-continents will make the planet too hot, lower volcanic CO2 as continents jam together may counteract this – perhaps future Snowball Earths are possible after all. Most importantly, warned Dr. Dutkiewicz, human-induced warming is accelerating climate change far beyond anything seen in Earth’s past.


Sources

University of Sydney | Adriana Dutkiewicz, Andrew S. Merdith, Alan S. Collins, Ben Mather, Lauren Ilano, Sabin Zahirovic, R. Dietmar Müller. Duration of Sturtian “Snowball Earth” glaciation linked to exceptionally low mid-ocean ridge outgassing. Geology, 2024; DOI: 10.1130/G51669.1


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