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Antarctica , which is almost four times the size of the United States , is almost whole cover by a miles - thick layer of Methedrine .
But the South Pole has n’t always been frozen . So when was the last timeAntarcticawas meth - spare ?
Unlike today, Antarctica hasn’t always been covered in ice.
This ice cap formed comparatively recently in geologic term , expert told Live Science . " I guess most people would say 34 million age ago was when the ice plane first organize in Antarctica , " saidEric Wolff , a paleoclimatologist at the University of Cambridge . " [ antecedently ] most of it would have been like northern Canada today — tundra and cone-bearing forest . "
Global temperature are a key factor mold the extent of ice insurance coverage . Around 50 million years ago , the reality was about 25 degrees Fahrenheit ( 14 degrees Celsius ) warm than it is today , but temperatures steady decreased over the following 16 million age . By 34 million old age ago — a fourth dimension stop known as the Eocene - Oligocene boundary — the clime was 14.4 F ( 8 C ) warmer than it is today .
But what spark off this temperature drop , and was that all it pick out for the internal-combustion engine sail to form ?
Unlike today, Antarctica hasn’t always been covered in ice.
interrelate : Which is colder : The North or South Pole ?
" There are two factors , and plausibly both were in play , " Wolff told Live Science . " One of them is a alteration in the C dioxide assiduity of the atmosphere , and the other is the movements of the continents and , in particular , the possible action up of the Drake Passage , " the pass between South America and Antarctica that connects the South Atlantic with the South Pacific .
The morecarbon dioxidethat ’s in the atmosphere , the more heat is trapped and the warmer the planet is .
From about 60 million to 50 million year ago , the carbon dioxide density in Earth ’s atmosphere was really high — somewhere around 1,000 to 2,000 part per million , or between 2.5 to 5 timestoday ’s levels , saidTina van de Flierdt , a geochemist at Imperial College London .
" But we know that the CO2 in the atmosphere derive down across that Eocene - Oligocene boundary , " she told Live Science . This decrement in atmospherical CO2 would have been attach to by a cooling system of the global climate , she added , probably tip Earth over a room access and allowing ice sheets to form .
However , there was also likely localized temperature reduction on the Antarctic continent due toplate tectonics , Wolff said . Around this prison term , South America and Antarctica lastly separated , opening up what ’s now the Drake Passage .
" This lead to what we call a circumpolar stream — piss going the right way around Antarctica in a circle , " Wolff allege . " This isolates Antarctica from the rest of the world and makes it much hard for warm line mass to get across the Southern Ocean and , therefore , makes Antarctica colder . "
Plate tectonics also directly influenced carbon dioxide level , he added . John Rock weathering and volcanic activity are both part of the carbon cycle , so over thousands of days , geologic process can shift the balance of gases in the aura .
Although some dubiety remains , investigator are fairly confident about this transition 34 million years ago thanks to the chemical signature in rock sediments . Oxygen atoms subsist in two variety : oxygen-16 ( rough-cut oxygen ) and oxygen-18 ( heavy atomic number 8 ) . Continental ice contains a higher dimension of the lighter oxygen-16 , meaning the ocean — and , therefore , the shells of small sea creature — contain a gamy percentage of oxygen-18 when ice sheets are bigger .
— Do the Pacific Ocean and the Atlantic Ocean mix ?
— When did Antarctica become a continent ?
— Will Antarctica ever be inhabitable ?
" By await at the oxygen isotopes in the carbonate shells of small ocean creatures in ocean sediments , you see a jump around 34 million long time ago , which hoi polloi take as being because the [ lightsome ] oxygen isotope is pass away onto the continent of Antarctica , " Wolff explained .
As for whether Antarctica could ever be ice - free again , " It ’s by all odds possible , van de Flierdt say . " major planet Earthhas done it before . Planet Earth could do it again . " While it ’s unbelievable that human activeness will lead to the complete melt of the ice sheet , it ’s important we do everything possible to trammel the loss of ice from the Antarctic now , she added . " It ’s in our hands to avoid the worst - case scenario , " van de Flierdt say .
