What role did underwater volcanoes play in altering conditions during “Snowball Earth” and helping initiate animal life?
A quite significant one, according to researchers out from the University of Southampton. According to their study, carbon dioxide released from volcanic activity warmed the atmosphere during this time period when much of Earth’s surface was ice-covered – sufficient enough to rapidly melt the ice cover and help catalyze animal life on the planet.
The findings shed some light on how Earth turned from icehouse to greenhouse.
About 720 to 640 million years ago, the planet was locked in the so-called Snowball Earth period, where much of its surface was covered in ice for tens of millions of years. Part of this era was explosive underwater volcanoes.
Snowball Earth was triggered by the breakup of supercontinent Rodinia, which changed ocean chemistry (through increased river discharge into the ocean) and reduced carbon dioxide in the atmosphere, propelling the planet into severe icehouse conditions.
How then did this extreme ice age end?
Volcanoes, according to the authors, played a key role. Carbon dioxide from volcanic activity warmed the atmosphere enough to quickly melt the ice cover.
“When volcanic material is deposited in the oceans it undergoes very rapid and profound chemical alteration that impacts the biogeochemistry of the oceans,” said lead study author Dr. Tom Gernon in a press release.
A puzzling feature of this extraordinary transition from icehouse to greenhouse are thick deposits referred to as “cap carbonates,” formed in the warm waters after that period and remain visible today in places such as China and Namibia, explained Dr. Gernon in his separate article on the study.
The authors said that during Rodinia’s breakup, mid-ocean ridge spanning tens of thousands of kilometers formed over millions of years, with the lava in shallow waters creating large volumes of hyaloclastite or glassy pyroclastic rock.
Rapid chemical phenomena followed as the deposits amassed on sea floor, releasing huge calcium, magnesium, and phosphorus amount into the ocean.
Based on the team’s calculations, the chemical buildup is enough to explain the formation of the cap carbonates when the Snowball period ended.
Thus the process helped explained the extraordinarily high phosphorus levels in the ocean, believed to catalyze Earth’s animal life.
Dr. Gernon said that one of the most extreme climate phases on Earth would hardly be thought to stimulate the rise of complex life forms. “But this does now appear to be the case.”
The findings were published in the journal Nature.