Chinese scientists propose new life evolution mechanisms on "Snowball Earth"

HEFEI, Sept. 8 (Xinhua) -- Scientists believe that 600 million years ago, the Earth's surface twice became entirely or nearly entirely frozen, a stage known as Snowball Earth. Chinese scientists have proposed new mechanisms for the evolution of life during that period.

The Cryogenian Sturtian and Marinoan Snowball Earth glaciations bracket is a nonglacial interval during which Demosponge and green-algal biomarkers first appeared. To understand the relationships between environmental perturbations and early animal evolution, a research group led by Shen Yan'an of the University of Science and Technology of China measured sulfur and mercury isotopes from south China.

Their research, published in the journal Science Advances on Thursday, shows that Snowball Earth may have provided a bottleneck for some preglacial life-forms but also suggests that melt ponds on the surface of ice and zones of sublimation were potential nurseries for the diversification of life.

The research team selected geological boreholes up to 100 meters deep for systematic analysis. They found that in the early period of Snowball Earth melting, the chemical composition of seawater was significantly different from modern seawater, and changes in mercury isotopes suggest enhanced volcanism.

Based on that, the researchers proposed that the sudden deglaciation caused a sudden depressurization of terrestrial magma chambers, thereby inducing magma activity and volcanic eruptions.

"It's like moving a huge boulder from the ground, and the suppressed underground magma suddenly erupted. The volcanic eruptions lasted for about 100,000 years, promoting a chain reaction in the Earth's environment," said Li Menghan, a member of the research team.

According to Shen, their research results have practical significance.

"We are currently in a period of global warming, and some glaciers are melting, which may also induce volcanic eruptions and cause hypoxia in the ocean. These are all warnings that we must pay attention to the possible chain reaction of the Earth's environment," Shen said. 

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