Until now, no one was sure why Earth fell into an extreme ice age 717 million years ago and stayed that way for 56 million years.
Now Australian researchers may have solved the mystery.
Using computer models, they analyzed how the continents moved over time. They believe the sudden drop in temperature was due to a decrease in carbon dioxide emissions. Carbon dioxide traps heat from the sun. If carbon dioxide in our atmosphere plummeted, it could cause the “Snowball Earth” of 700 million years ago.
But what caused carbon dioxide levels to drop so dramatically? And why did it last 56 million years? Says the main researcher Adriana Dutkiewicz: “Today, humans have a large impact on CO2 in the atmosphere. But in the past there were no humans, so everything was basically modulated by geological processes.”
They suspected that the changing carbon dioxide levels could be due to volcanic activity. Or rather, the lack thereof.
The team observed the movement of tectonic plates after the breakup of Ronda, the ancient supercontinent. The model showed that as the smaller continents moved further away from each other, the length of the mid-ocean ridge changed in length. A second computer model then analyzed the amount of carbon dioxide emitted by underwater volcanoes along the mid-ocean ridge.
The model showed that a record low in volcanic carbon dioxide emissions coincided perfectly with the start of the so-called Sturt Ice Age. The amount of atmospheric carbon dioxide was about half of what it is today. For the next 56 million years, carbon dioxide remained relatively low.
Co-author Dietmar Müller said: “We believe that the Sturtian Ice Age began due to a double whammy: a plate tectonic reorganization (minimized) volcanic degassing, while simultaneously a continental volcanic province in Canada began… to consume atmospheric carbon dioxide”.
Although the models seem to explain this mysteriously long ice age, it is difficult to prove it. Nobody knows what the ancient seabed was like. “In geology, there are no definitive answers,” Dutkiewicz says. “But… we can suggest that this was a very likely process.”