The Sturtian “Snowball Earth” glaciation, occurring between 717 and 661 million years ago, is widely recognized as Earth’s most severe period of icehouse climate. In a recent investigation, geoscientists from the University of Sydney and the University of Adelaide employed plate tectonic modeling to ascertain the most probable genesis of this profound glacial episode.
An artist’s impression of the ‘Snowball Earth.’ Image credit: Oleg Kuznetsov, http://3depix.com / CC BY-SA 4.0.
“Envision a scenario where our planet was almost entirely encased in ice. This is precisely what transpired approximately 700 million years ago,” commented lead author Dr. Adriana Dutkiewicz, a researcher affiliated with the University of Sydney.
“The entire globe, from its polar regions to its equatorial zones, was enveloped in ice, and temperatures experienced a dramatic decline. Nonetheless, the precise drivers of this phenomenon remained an unresolved query.”
“Our current hypothesis is that we have deciphered the enigma: a period of exceptionally low volcanic carbon dioxide emissions, exacerbated by the weathering of a substantial accumulation of volcanic rocks in what is presently Canada; a geological process that effectively sequesters atmospheric carbon dioxide.”
The Sturtian glaciation, named in honor of the 19th-century European colonial explorer of central Australia, Charles Sturt, spanned from 717 to 660 million years ago, an era significantly predating the existence of dinosaurs and complex terrestrial flora.
“While various explanations have been put forth regarding the initiation and cessation of this extreme ice age, the most perplexing aspect is its astonishing duration of 57 million years—a timescale that is remarkably difficult for us humans to fully comprehend,” stated Dr. Dutkiewicz.
Dr. Dutkiewicz and her team utilized a plate tectonic model to illustrate the evolutionary trajectory of continents and oceanic basins during a period following the fragmentation of the ancient supercontinent Rodinia.
This model was subsequently integrated with a computational simulation designed to quantify the carbon dioxide degassing from submarine volcanoes situated along mid-ocean ridges—the geological loci where tectonic plates diverge and new oceanic crust is generated.
It was quickly apprehended that the commencement of the Sturtian glaciation coincided precisely with an unprecedented nadir in volcanic carbon dioxide emissions.
Furthermore, the outflow of carbon dioxide remained comparatively subdued throughout the entirety of the glaciation period.
“At this geological juncture, no multicellular animal life or terrestrial plant species inhabited the Earth,” Dr. Dutkiewicz noted.
“The atmospheric concentration of greenhouse gases was almost exclusively governed by the outgassing of carbon dioxide from volcanic activity and by processes involving the weathering of silicate rocks, which serve to consume carbon dioxide.”
“Geology exerted a dominant influence on the climate during this epoch,” remarked co-author Professor Dietmar Müller, a researcher at the University of Sydney.
“We posit that the Sturtian ice age was precipitated by a synergistic combination of factors: a reorganization of plate tectonics led to a minimization of volcanic degassing, while concurrently, a continental volcanic province located in Canada began undergoing erosion, thereby consuming atmospheric carbon dioxide.”
“The consequence was a precipitous reduction in atmospheric carbon dioxide to levels conducive to glaciation—levels we estimate fell below 200 parts per million, less than half of current atmospheric concentrations.”
The current research undertaken by the team prompts intriguing considerations regarding the long-term future of our planet.
A recent theoretical framework proposed that over the ensuing 250 million years, Earth might evolve towards the formation of Pangea Ultima, a supercontinent so intensely hot that mammalian life could face extinction.
However, Earth is also presently trending toward reduced volcanic carbon dioxide emissions as continental collisions escalate and tectonic plate movement decelerates.
Consequently, it is conceivable that Pangea Ultima could undergo a transformation into a frozen state once more.
“Regardless of what the future portends, it is important to underscore that geological climate change, the kind investigated in this study, unfolds at an exceedingly gradual pace,” Dr. Dutkiewicz emphasized.
“In contrast, according to NASA, human-induced climate change is progressing at a rate approximately ten times faster than any previously observed geological climate shift.”
The study has been published in the esteemed journal Geology.
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Adriana Dutkiewicz et al. Duration of Sturtian “Snowball Earth” glaciation linked to exceptionally low mid-ocean ridge outgassing. Geology, published online February 7, 2024; doi: 10.1130/G51669.1
