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Some 720–640 million years ago, researchers believe, our planet was covered in ice. It's not entirely clear what the Earth looked like during that period of time, but a recent study published in Nature suggests that underwater volcanoes were a key element of the millions-year-long event—and that these volcanoes helped trigger life later on.

Scientists link the Earth's transformation into an icy rock to the breakup of the Rodinia land mass. They theorize that the continental break poured river water into the ocean, which in turn lead to ice buildups that cooled the planet. Study co-author Eelco Rohling noted that, "Eventually land-based volcanism pumps so much CO2 into the atmosphere that it pushes the planet out of the Snowball Earth phase."

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But that theory fails to explain a puzzling feature of Snowball Earth: cap carbonates, or carbonate rock layers that appeared after the glaciation period. The researchers examined this feature, and concluded that underwater volcanoes must have been involved. The university offers more in a statement:

During the breakup of Rodinia, tens of thousands of kilometres of mid-ocean ridge were formed over tens of millions of years. The lava erupted explosively in shallow waters producing large volumes of a glassy pyroclastic rock called hyaloclastite. As these deposits piled up on the sea floor, rapid chemical changes released massive amounts of calcium, magnesium and phosphorus into the ocean.

Lead author Tom Gernon added, "When volcanic material is deposited in the oceans it undergoes very rapid and profound chemical alteration that impacts the biogeochemistry of the oceans. We find that many geological and geochemical phenomena associated with Snowball Earth are consistent with extensive submarine volcanism along shallow mid-ocean ridges.”

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He added that the volcanic activity can be considered a kind of trigger for life, saying, "This process also helps explain the unusually high oceanic phosphorus levels, thought to be the catalyst for the origin of animal life on Earth.”

Rohling added that hyaloclastite eruptions, or underwater volcanic eruptions, " [turn] the ocean very rich in calcium, magnesium, silicon and phosphorus… the phosphorus is a nutrient generating huge algal blooms which fix carbon and release oxygen, essential for the development of animal life."

Thanks, volcanoes.

Danielle Wiener-Bronner is a news reporter.