It’s hard to believe, but about 700m years ago it’s thought that our planet completely froze over with little to no liquid ocean or lakes exposed to the atmosphere, even in the tropics. But what tipped Earth’s climate into “Snowball Earth” state? A new study suggests a cold climate and massive volcanic eruptions set the scene.
The Franklin eruptions – about 720m years ago – spewed out vast amounts of fresh rock, stretching from what is now Alaska, through northern Canada to Greenland. Similarly large eruptions have happened at other times, but this one happened to coincide with an already cold climate. And combined with a lack of plants (they hadn’t evolved yet) these eruptions exposed a huge carpet of fresh rock to intense weathering.
Chemical reactions associated with weathering remove carbon dioxide from the air. By modelling the climate impact, researchers have shown that rapid erosion over such a large area could have pulled down enough carbon dioxide to tip Earth into a snowball state. The findings, which are published in the Journal of Geophysical Research: Planets, also show that similar-sized volcanic eruptions at other times in Earth’s history failed to generate snowball conditions because they occurred when the background climate was hotter, or at times when vegetation cover slowed the rate of erosion.