Why Earth once sang a song of ice and fire

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Mar 23, 2017

Long before George R.R. Martin spawned the fandom that would launch a million “Winter is coming” memes, there was a song of ice and fire playing out on Earth. Researchers at Harvard University have now ignited a new hypothesis as to how “Snowball Earth” emerged out of volcanic fires after years of frozen theories. You know nothing, Jon Snow.

The Neoproterozoic Snowball Earth event (aka Sturtian Snowball Earth) plunged Earth into a pole-to-pole deep freeze around 717 million years ago. Recently published in Geophysical Research Letters, their findings explore the paradox of enormous volcanic eruptions shaking what is now the area that extends form Alaska to Greenland—around the same time the entire planet was headed into a proverbial freezer. Volcanic activity obviously has a tremendous effect on the environment. What the team led by Harvard professors Francis Macdonald and Robin Wordsworth were burning to find out was how the heated outbursts and intense cold were scientifically related.    

"It is not unique to have large volcanic provinces erupting," Wordsworth, assistant professor of Environmental Science and Engineering at the Harvard John A. Paulson School of Engineering and Applied Science, explained. "These types of eruptions have happened over and over again throughout geological time but they're not always associated with cooling events. So, the question is, what made this event different?"

Macdonald and Wordsworth first theorized that the basaltic rock which results from the hardening of magma could have decomposed into magnesium and calcium that interacted with atmospheric carbon dioxide and caused temperatures to drop. What was problematic about this assumption was that the cooling, which is believed to have happened relatively quickly, would have taken millions of years with this process. Radio-isotopic dating of Arctic volcanic rocks also told them that the nearly simultaneous burning and freezing occurred as a far more precise coincidence. The answer? Aerosols.

What Snowball Earth is imagined to have looked like over 700 million years ago.

While the thought of aerosols may remind you of hairspray, the aerosols taken into account by Macdonald and Wordsworth were actually suspensions of particles dispersed evenly throughout the gases released by volcanic activity. Sulfur dioxide was most likely the main catalyst of Earth’s extended winter. Previous studies have shown proof of volcanic rocks exploding through sulfurous sediments that burst into the upper atmosphere, especially in the tropopause (between the troposphere and the stratosphere), as clouds of sulfur dioxide. Once sulfur dioxide reaches the tropopause, it is especially effective at blocking the solar radiation that would be necessary to heat our planet.

This wasn’t a one-off blast of fiery plumes. The team believes that it must have taken about a decade for enough aerosols to create effective radiation blockage in the atmosphere—at least enough to say winter would be coming for a long, long time.

The icy Earth of hundreds of millions of years ago is an opportunity for scientists to better understand ancient mass extinctions, climate change on exoplanets, and even possible methods of geoengineering that could eventually slow, if not reverse the effects of global warming.

"We know that Earth is a dynamic and active place that has had sharp transitions,” said Wordsworth. “There is every reason to believe that rapid climate transitions of this type are the norm on planets, rather than the exception."

(via Phys.org)

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