Explosive underwater volcanoes played a key role in “Snowball Earth,” the hypothesized period of deep freeze that engulfed the planet approximately 640 to 720 million years ago, according to new research led by scientists from the University of Southampton in England.
During this period of glaciation, the majority of the Earth’s surface was covered in ice for several million years, and while many aspects of this hypothesis remain enigmatic, many experts believe that the breakup of the supercontinent Rodinia increased river discharge into the oceans.
This, in turn, altered the chemistry of the oceans and reduced atmospheric carbon dioxide levels, ultimately causing global ice coverage to increase and covering the land surface in a deep freeze that effectively brought an end to continental weathering. This “Snowball Earth” state remained until CO2 released through volcanic activity warmed the atmosphere enough to melt the ice.
However, as the Southampton-led team of researchers pointed out, the current models failed to adequately explain one of the most mysterious factors of this rapid deglaciation: the formation of hundreds of meters worth of cap carbonates, a type of carbonate rock with distinctive textures, in the warm, post-Snowball Earth waters.
Volcanic processes may have also helped kick-start animal life
In a study published in Monday’s edition of the journal Nature Geoscience, lead author Dr. Tom Gernon, a lecturer in Earth science at the university, and his colleagues explained that the drastic changes in ocean chemistry were the most likely the result of underwater volcanism.
“When volcanic material is deposited in the oceans it undergoes very rapid and profound chemical alteration that impacts the biogeochemistry of the oceans,” Dr. Gernon 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.”
When the supercontinent Rodinia split apart, thousands of kilometers of mid-ocean ridges were formed over a several-million year span. Explosive volcanic eruptions taking place in the shallow waters caused significant amounts of hyaloclastite, a kind of glassy pyroclastic rock, to be produced. As the quantity of hyaloclastite deposits increased, rapid chemical changes took place, releasing copious amounts of calcium, magnesium, and phosphorus into the ocean.
“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,” said Dr. Gernon. “This process also helps explain the unusually high oceanic phosphorus levels, thought to be the catalyst for the origin of animal life on Earth.”
—–
Feature Image: Gary Hincks
Comments