Scientists uncover a 700-million-year-old climate mystery

Australian geologists have identified reduced volcanic carbon dioxide emissions and rock weathering in Canada as major factors behind an intense ice age 700 million years ago. Their research, based on plate tectonic models and geological evidence from South Australia, highlights the sensitivity of Earth's climate and natural heat-regulating mechanisms, contrasting the slow pace of geological climate change with rapid changes caused by human activities. Credit: NASA

Volcanic carbon emissions reached an all-time low, triggering a global ice age that lasted 57 million years.

Australian geologists have used plate tectonic modeling to determine the most likely causes of Earth's extreme Ice Age climate, which occurred more than 700 million years ago.

The study published in geology, helps us understand the working of the thermostat built into the floor which prevents the floor from getting stuck in overheat mode. It also shows how sensitive the global climate is to the concentration of carbon in the atmosphere.

“Imagine the Earth being almost completely frozen over,” said the study's lead author, ARC Future Fellow Dr. Adriana Dutkiewicz. “This is what happened about 700 million years ago; the planet was covered in ice from the poles to the equator and temperatures dropped. However, what caused this was an open question.”

Glacial deposits in the Flinders Ranges, South Australia

Glacial deposits of the Sturt Formation from the Sturt Glaciation approximately 717-664 million years ago in the northern Flinders Ranges, Australia, near the Arkarola Wildlife Reserve. Lead author Dr Adriana Dutkiewicz from the University of Sydney's School of Earth Sciences points to a thick layer of glacial deposits. Credit: Professor Dietmar Müller/University of Sydney

“We now think we have solved the puzzle: a historic decline in volcanic carbon dioxide emissions, aided by the weathering of a large pile of volcanic rock in what is now Canada, a process that absorbs atmospheric carbon dioxide.

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Geological insights from the Flinders Ranges

The project is inspired by the glacial debris left behind by ancient glaciation from this period which can be strikingly observed in the Flinders Range in South Australia.

A recent geological field trip to the mountain range, led by co-author Professor Alan Collins from the University of Adelaide, prompted the team to use… University of Sydney EarthByte computer models to investigate the cause and extremely long duration of this ice age.

Between 717 and 660 million years ago, the Earth was covered in snow and ice, an ice age lasting 57 million years. Geologists at the University of Sydney, led by Dr. Adriana Dutkiewicz and Professor Dietmar Müller, have found the likely culprit: all-time low levels of volcanic carbon dioxide in the atmosphere. This video shows the movement of continents (gray) and plate boundaries (orange) 850 to 540 million years ago. (Snowflakes appear during “snowball Earth” periods.) Credit: Ben Mather and Dietmar Müller/University of Sydney

Sturtian glaciation and plate tectonics

The Extended Ice Age, also called the Sturtian Glaciation after the 19th-century European colonial explorer of central Australia, Charles Sturt, lasted from 717 to 660 million years ago, a period before the presence of dinosaurs and complex plant life on Earth.

Dr Dutkiewicz said: 'Various reasons have been proposed behind the beginning and end of this extreme ice age, but the most mysterious aspect is why it lasted for 57 million years – a period of time that is difficult for us humans to imagine.'

The team returned to a plate tectonic model that shows the evolution of continents and ocean basins sometime after the breakup of the ancient supercontinent Rodina. They connected it to a computer model that calculates carbon dioxide2 Underwater volcanoes degas gases along mid-ocean ridges – sites where plates diverge and generate new ocean crust.

Adriana Dutkiewicz

Dr Adriana Dutkiewicz from the University of Sydney's School of Geosciences in the Flinders Ranges of South Australia. Credit: University of Sydney

The role of carbon dioxide and geological climate change

They soon realized that the beginning of the Sturtian Ice Age was precisely linked to the lowest volcanic carbon dioxide ever recorded2 emissions. In addition, Inc2 Outflow remained relatively low throughout the duration of the ice age.

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“At this time, there were no multicellular animals or land plants on Earth,” Dr. Dutkiewicz said. “The concentration of greenhouse gases in the atmosphere was determined almost entirely by carbon dioxide.”2 The release of gases from volcanoes and through silicate rock weathering processes, which consume carbon dioxide2“.

Co-author Professor Dietmar Müller from the University of Sydney said: “Geology governed the climate at this time. We believe that the Sturtian Ice Age was initiated by a double whammy: the reorganization of tectonic plates reduced the degassing of volcanic gases to a minimum, while a continental volcanic province began.” In Canada in erosion, resulting in the consumption of carbon dioxide in the atmosphere.2.

Glacial deposits of the Stirt Formation in South Australia

A view towards the Arkarola Wildlife Reserve, Flinders Ranges, where glacial deposits of the Sturt Formation from the Sturt Glaciation about 717-664 million years ago form a prominent ridge in the middle of the image on the left. Credit: Professor Dietmar Müller/University of Sydney

“The result was carbon dioxide in the atmosphere2 It dropped to the level at which glaciation begins, which we estimate to be less than 200 ppm, less than half of today's level.

The team's work raises interesting questions about Earth's long-term future. a Proposed modern theory That over the next 250 million years, Earth will evolve toward Pangea Ultima, a supercontinent so hot that mammals may become extinct.

However, the Earth is also currently on a path of declining volcanic carbon dioxide2 Emissions, with increased continental collisions and plate slowing. So, maybe Pangea Ultima will turn into a snowball again.

“Whatever the future holds, it is important to note that geoclimate change, of the type studied here, occurs very slowly,” Dr. Dutkiewicz said. NASAHuman-induced climate change is occurring ten times faster than we have ever seen before.

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Reference: “Duration of Sturtian ‘snowball terrestrial’ glaciation associated with exceptionally low mid-ocean outgassing” by Adriana Dutkiewicz, Andrew S. Meredith, and Alan S. Collins, Ben Mather, Lauren Elano, Sabine Zahirovic, and R. Dietmar Müller.

The study was funded by the Australian Research Council.

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