Approximately 720 to 640 millions years ago, most of the Earth's surface was lined with ice due to a glaciation that didn't let up for millions of years. Although many features of this ancient glaciation remain uncertain to scientists, new research from a team at the University of Southampton suggests that explosive underwater volcanoes were a major feature during this time period, also referred to as "Snowball Earth."
In terms of what is known, scientists believe that the breakup of the supercontinent Rodinia is at the root of the creation of Snowball Earth - after stimulating increased river discharge into the ocean, current theories point to a change in ocean chemistry that led to global ice coverage that caused the Earth to endure severe icehouse conditions. However, one thing that this model does not explain is features of rapid deglaciation that can be seen from this time, including the formation of "cap carbonates," which are deposits in warm waters that are hundreds of meters thick.
"When volcanic material is deposited in the oceans it undergoes very rapid and profound chemical alteration that impacts the biogeochemistry of the oceans," Tom Gernon, lead author of the study, said in a press release. "We find that many geological and geochemical phenomena associated with Snowball Earth are consistent with extensive submarine volcanism along shallow mid-ocean ridges."
The breaking of Rodinia lead to the creation of mid-ocean ridges over the course of millions of years - lava from these volcanoes is hypothesized to have erupted in shallow water, created large amounts of hyaloclastite, which refers to the glassy, pyroclastic rocks that piled on the sea floor. This piling in turn lead to chemical changes in the ocean such as the release of massive amounts of calcium, magnesium and phosphorous.
"We calculated that, over the course of a Snowball glaciation, this chemical build-up is sufficient to explain the thick cap carbonates formed at the end of the Snowball event," Gernon explained. "This process also helps explain the unusually high oceanic phosphorus levels, thought to be the catalyst for the origin of animal life on Earth."
The findings were published in the Jan. 18 issue of Nature Geoscience.
