He Sturtian ‘Snowball Earth’ Glaciation (717 to 661 million years ago) is considered the most extreme interval of greenhouse climate in Earth’s history. In a new study, geologists from the University of Sydney and the University of Adelaide used plate tectonic models to determine what likely caused the Sturtian glaciation.
“Imagine the Earth almost completely frozen. That’s exactly what happened about 700 million years ago,” said lead author Dr Adriana Dutkiewicz, a researcher at the University of Sydney.
“The planet was covered in ice from the poles to the equator and temperatures fell. However, what caused this has been an open question.”
“Now we think we have solved the mystery: historically low volcanic carbon dioxide emissions, helped by the erosion of a large pile of volcanic rocks in what is now Canada; a process that absorbs atmospheric carbon dioxide.”
The Sturtian Glaciation, named after the 19th-century European colonial explorer in central Australia, Charles Sturt, extended from 717 to 660 million years ago, a period long before dinosaurs and complex plant life existed on earth. .
“Several causes have been proposed for the triggering and ending of this extreme ice age, but the most mysterious aspect is why it lasted 57 million years, a time span difficult for humans to imagine,” said Dr. Dutkiewicz. .
Dr. Dutkiewicz and his colleagues used a plate tectonic model that shows the evolution of continents and ocean basins at a time after the breakup of the ancient supercontinent Rodina.
They connected it to a computer model that calculates the outgassing of carbon dioxide from underwater volcanoes along mid-ocean ridges, the sites where plates diverge and new oceanic crust is born.
They soon realized that the onset of the Sturtian glaciation correlates precisely with a record low in volcanic carbon dioxide emissions.
Furthermore, carbon dioxide efflux remained relatively low throughout the ice age.
“At that time, there were no multicellular animals or land plants on Earth,” Dr. Dutkiewicz said.
“The concentration of greenhouse gases in the atmosphere was almost entirely dictated by the release of carbon dioxide from volcanoes and by the erosion processes of silicate rocks, which consume carbon dioxide.”
“Geology dominated the climate at that time,” said co-author Professor Dietmar Müller, a researcher at the University of Sydney.
“We believe the Sturtian Ice Age occurred due to a double whammy: a reorganization of tectonic plates minimized volcanic degassing, while simultaneously a continental volcanic province in Canada began to erode, consuming atmospheric carbon dioxide.”
“The result was that atmospheric carbon dioxide fell to a level at which glaciation occurs, which we estimate to be below 200 parts per million, less than half the current level.”
The team’s current work raises intriguing questions about Earth’s long-term future.
A recent theory proposed that over the next 250 million years, the Earth would evolve toward Pangea Ultimaa supercontinent so hot that mammals could become extinct.
However, the Earth is also currently on a trajectory of lower volcanic carbon dioxide emissions, as continental collisions increase and plates slow down.
So maybe Pangea Ultima will snowball again.
“Regardless of what the future holds, it is important to note that geologic climate change, of the type studied here, occurs extremely slowly,” Dr. Dutkiewicz said.
“According to NASA, human-induced climate change is occurring at a rate 10 times faster than we have seen before.”
He study appears in the magazine geology.
Adriana Dutkiewicz et al. Duration of Sturtian “Snowball Earth” glaciation related to exceptionally low degassing of mid-ocean ridges. geology, published online February 7, 2024; doi:10.1130/G51669.1