Global cooling – why the Earth used to be a giant “snow globe”, scientists have found

The Earth became a “giant snow globe” about 700 million years ago as a result of an extreme ice age. Then our planet was almost completely frozen – it was covered with ice from the poles to the equator. The question that caused this remains open for a long time.

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Australian geologists from the University of Sydney, having carried out tectonic modeling, have established the probable causes of such an anomalous period in the history of our planet. The press service of the university reports this.

The long ice age spanned from 717 to 660 million years ago – long before the advent of dinosaurs and complex plant life on land.

Various explanations have been put forward for what triggered and ended this extreme ice age, but the most puzzling aspect is why it lasted 57 million years—a length of time that is difficult for us humans to imagine, the researchers note.

Scientists were prompted to a possible explanation by striking glacial debris left by ancient glaciations from the period, which can be seen in the Flinders Ranges in South Australia.

As part of the study, scientists:

• applied a plate tectonic model that shows the evolution of continents and ocean basins in the period after the breakup of the ancient supercontinent Rodinia, which formed 1.1 billion years ago and broke up about 750 million years ago and included almost all of the land;
• coupled it with a computer model that calculates CO2 degassing from undersea volcanoes along mid-ocean ridges—places where plates move apart and new oceanic crust is born.

As a result, scientists found that:

• the onset of the ice age coincides precisely with the historical minimum of volcanic CO2 emissions;
• in addition, CO2 flux remained relatively low throughout the Ice Age.

At this time there were no multicellular animals or land plants on Earth. The concentration of greenhouse gases in the atmosphere was almost entirely determined by CO2 emissions from volcanoes and weathering processes of silicate rocks, the researchers note.

Thus, the researchers believe, a large-scale ice age began as a result of a “double blow”:

1. plate tectonic reorganization has reduced volcanic degassing to a minimum;
2. The volcanic region, then located in what is now Canada, began to collapse, causing large quantities of volcanic rock to weather, a process that absorbs atmospheric carbon dioxide.

As a result, CO2 levels in the atmosphere fell to glaciation levels—we estimate below 200 parts per million, less than half of today’s levels, the researchers note.

According to scientists, this discovery raises intriguing questions about the long-term future of the Earth:

• newest theories suggest that over the next 250 million years, Earth will evolve into Pangea Ultima, a supercontinent so hot that mammals could go extinct;
• however, the Earth is now also on a downward trajectory in volcanic CO2 emissions as continental collisions intensify and plate motion slows. So perhaps Pangea Ultima will turn into a snow globe again.

Whatever the future holds, it is important to note that geological climate changes such as those being studied occur extremely slowly. According to NASA, anthropogenic climate change is occurring 10 times faster than we previously observed, the researchers summarize.

Source: Racurs

David

I am David Wyatt, a professional writer and journalist for Buna Times. I specialize in the world section of news coverage, where I bring to light stories and issues that affect us globally. As a graduate of Journalism, I have always had the passion to spread knowledge through writing.