Volcanoes kick-start life

Some 720–640 million years ago, the Earth was virtually frozen, buried in massive ice sheets with surface temperatures as low as -50°C. One of the big mysteries of this ‘Snowball Earth’ is how and why the ocean chemistry changed as the ice suddenly melted. Dr Tom Gernon, Associate Professor in Earth Science at the University, sheds light on the important role volcanoes played in this extreme climate state.

Geoscientists believe that Snowball Earth was triggered by the break-up of a supercontinent called Rodinia. The resulting fragments were clustered near the equator where there are higher temperatures – resulting in increased evaporation of water from the oceans, which led to more precipitation. This also meant faster rates of chemical weathering: rain water reacting with mineral grains in rocks to flush dissolved minerals via rivers into the oceans. “This changed the ocean chemistry and used up a lot of atmospheric CO2, which normally traps heat inside the atmosphere – propelling the Earth into a severe ice age,” says Tom.

“Add to this the fact that, once frozen, the Earth was largely white, reflecting rather than absorbing the sun’s energy, the planet became locked into the Snowball Earth state for tens of millions of years.”

One of the big mysteries for geoscientists is how and why the ocean chemistry changed as the ice suddenly melted, explains Tom. “But now our study, published in Nature Geoscience, has shed light on this conundrum, demonstrating how underwater volcanoes during Snowball Earth played a crucial role in this transformation. The results help explain how our planet got oxygen in its atmosphere and oceans – enabling life to evolve from single-celled organisms into animals.”

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