(p. D4) Around 717 million years ago, Earth’s humid landscapes and roiling blue waters transformed into a frigid, barren world. Scientists nicknamed this stage of geological history, and others like it, Snowball Earth.
What exactly froze the planet nearly solid has been a mystery, as has how it remained that way for 56 million years. On Wednesday, a team of researchers at the University of Sydney said they have it figured out. Earth’s glaciation, they say, may have come from a global drop in carbon dioxide emissions, a result of fewer volcanoes expelling the gas into the atmosphere.
Less carbon dioxide makes it more difficult for Earth’s atmosphere to trap heat. If the depletion were extreme enough, they argued, it could have thrust the planet into its longest ice age yet.
The theory, published in the journal Geology, adds insight to the way geological processes influenced Earth’s past climate. It may also help scientists better understand trends in our current climate.
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Dr. Dutkiewicz and her colleagues turned their eyes to volcanoes because of a newly available model of Earth’s shifting tectonic plates. As the continents spread apart, they studied the changing length of the mid-ocean ridge — a chain of underwater volcanoes — predicted by the model.
The team then calculated the amount of volcanic gas emissions at the beginning of, and throughout, the ice age. Their results showed a drop in atmospheric carbon dioxide sufficient to initiate and sustain a 56-million-year glaciation.
A reduction in volcanic gas emissions has been proposed as an explanation for Snowball Earth before. But according to Dr. Dutkiewicz, this is the first time researchers have proved that the mechanism was viable through modeled computations.
For the full commentary, see:
(Note: ellipsis added.)
(Note: the online version of the commentary was updated February 12, 2024, and has the title “How Earth Might Have Turned Into a Snowball.”)
The paper in the journal Geology mentioned above is: