For the Earth to become as insensate as it was during the “ Snowball Earth ” era , and stay there , required a combination of a shake-up of the Earth ’s continents and the weathering of a vast volcanic province , scientist have argued . Another team , coincidentally publishing at the same time , blames an asteroid rather . However , at this degree , they have less evidence to point to .
The periods know asSnowball Earthmade our late ice ages calculate like a minor chill . Not only were there massive glaciers at the equator , but in one case the frigidness lasted an forecast 57 million year . It ’s still a puzzler how life-time survived .
While some scientistswork on that interrogative sentence , others want to know how such an event could have occurred . Changes to the Earth ’s scope , such as those that caused late cold periods , are not remotely sufficient . There ’s at least one common feature between the big case and its pale imitations , however – low levels of carbon dioxide .
Evidence of the Sturtian Snowball Earth is found in rocks worldwide. Here, Dr Adriana Dutkiewicz studies examples in the Flinders Range not far from the original discovery site.Image Credit: Professor Dietmar Müller/University of Sydney
As the master equipment driver of changes in Earth ’s temperature , there is no doubt carbon dioxide levels were very low during the Snowball Earth period , but that leave behind the interrogation of why .
“ We now think we have cracked the closed book , ” saidDr Adriana Dutkiewiczof the University of Sydney in astatement . “ Historically low volcanic atomic number 6 dioxide discharge , help by weathering of a prominent pile of volcanic rocks in what is now Canada . ”
“ At this time , there were no multicellular animals or country plants on Earth , ” Dutkiewicz noted . “ The nursery gas compactness of the atmosphere was almost entirely dictated by CO2outgassing from volcanoes and by silicate sway brave processes , which squander CO2 . ”
Evidence for the weathering part is easy to find . TheFranklin Igneous Provincewas by far the largest volcanic state on Earth at the time . Once its growth , and the company carbon release , stop , exposure to air and water necessarily led to chemical changes that would have absorbed carbon dioxide from the ambiance .
That would not be enough on its own , however . Once the Earth became covered in internal-combustion engine it ponder more sunlight back to quad , temporarily maintaining low temperatures . On the other manus , all that ice would also have slow up the pace of weathering . In normal circumstances , this would have do carbon copy dioxide levels to rebound , warm the planet again . The fact this did n’t happen , Dutkiewicz and co - authors indicate , indicates for tens of millions of years the release of CO2must have been as tedious as its remotion .
They fault this on continental movement at the clip . The longest Snowball Earth , known as the Sturtian afterthe gorgewhere evidence first emerged , coincided with a period where just 9 megatonnes of carbon were released each year . At that low rate , even the minimum weathering beneath thick piece of paper of glass would have been sufficient to keep atmospheric carbon low . This broken passing charge per unit mull over a relative famine of submerged volcano at mid - oceanic ridge , in turn a consequence of the bust - up ofRodinia , the supercontinent beforePangaea .
Looking one step further back in the chain , Dutkiewicz tell IFLScience , that obligation lies with mantle convection processes , but “ the problem [ of what make them ] is not well understood . This is an area of vivid subject area and has been for a long time . ”
Almost the intact Earth froze over at least once more , in the Marinoan glaciation . Although Dutkiewicz believes there is some commons to the two glaciation ’ cause , she assure IFLScience : “ Marinoan was much brusk and happened a lot after . The Sturtian is the one that requires account . ”
At the same clock time as Dutkiewicz and colleagues were release their work , another paper reported that an asteroid bang of similar size to the “ dinosaur - sea wolf ” could have tipped the world into a exchangeable frozen nation . The authors of that newspaper conclude that such an outcome during a lovesome period , such as the Cretaceous , would have much more temporary result . When atomic number 6 dioxide levels were already low , however , it could trigger something much larger .
Dutkiewicz acknowledged to IFLScience that there could have been factors beyond the I her squad distinguish , but added the other paper “ is purely a climate modelling written report hypothesizing whether an asteroid impact of corresponding size to the Chicxulub impact could have actuate a worldwide glaciation . There is no evidence that such an asteroid impact really triggered ' Snowball Earth . ' It ’s a highly speculative scenario . In any case , even if such an impact had occurred , it is unbelievable to sustain a glaciation for very farsighted ( geologically speaking ) . ”
Dutkiewicz ’s work is open access inGeology . The asteroid hypothesis is open access inScience Advances .
