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takyon writes:

Harvard University researchers propose a new hypothesis to explain the largest glaciation event in Earth's history:

What caused the largest glaciation event in Earth's history, known as 'snowball Earth'? Geologists and climate scientists have been searching for the answer for years but the root cause of the phenomenon remains elusive. Now, Harvard University researchers have a new hypothesis about what caused the runaway glaciation that covered the Earth pole-to-pole in ice. The research is published in Geophysical Research Letters [DOI: 10.1002/2016GL072335] [DX].

Researchers have pinpointed the start of what's known as the Sturtian snowball Earth event to about 717 million years ago — give or take a few 100,000 years. At around that time, a huge volcanic event devastated an area from present day Alaska to Greenland.

Sulfur dioxide from volcanic eruptions can cool the planet more effectively if it can reach past the tropopause:

The height of the tropopause barrier all depends on the background climate of the planet — the cooler the planet, the lower the tropopause. "In periods of Earth's history when it was very warm, volcanic cooling would not have been very important because the Earth would have been shielded by this warm, high tropopause," said Wordsworth. "In cooler conditions, Earth becomes uniquely vulnerable to having these kinds of volcanic perturbations to climate."

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