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How the weathering of rocks cooled the Earth

A photo of Daniel Ibarra
Image credit: Courtesy Daniel Ibarra
Jul 3 2019
Fellow, Research, Stanford

Fifteen million years ago, the Earth’s climate entered into a period of slow, continuous cooling, and simultaneously the Antarctic ice sheet grew steadily larger. Finally, around 2.5 million years ago, Greenland became covered in ice, thrusting the Earth into its current bipolar ice age.

Geoscientists have been debating what brought about this global cooling for many years. Some argue that major mountain ranges such as the Andes, the Himalayas and the Alps started to form 15 million years ago, and that they accelerated erosion and the weathering of rocks. This theory posits that the formation of mountains drew more carbon dioxide from the atmosphere than processes such as volcanic eruptions were giving off, causing temperatures to continuously decrease.

A team of researchers from ETH Zurich, Stanford University and the German Research Centre for Geosciences (GFZ) in Potsdam has now demonstrated that this hypothesis is not accurate enough. Their study was published July 3 in the journal Nature.

“If you look back in the literature, the rate of weathering that was suggested would have dropped us into a full ice house and glaciated the entire world – and that’s not actually what happened,” said co-author Daniel Ibarra, a postdoctoral researcher in the Department of Geological Sciences at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth).

Co-author Daniel Ibarra is a 2013 EDGE-STEM Fellow and a 2016 Mentor.