ground ’s continents are incessantly changing , go and rearrange themselves over gazillion of class – affect Earth ’s climate and biology . Every few hundred million years , the continents blend to create monumental , populace - spanning supercontinents . Here ’s the past and future of Earth ’s supercontinets .
The Basics of Plate Tectonics
If we ’re going to talk about past and next supercontinents , we first need to sympathise how landmasses can move around and the continents can take on unexampled conformation . Let ’s start up with the basics – rocky planets like Earth have five interior spirit level : heading outwards , these are the inner core , outer inwardness , mantle , upper mantle , and the crust .
The crust and the part of the upper mantle take shape the lithosphere , a portion of our major planet that is basically unbending , solid rock and run to about 100 km below the planet ’s surface . Below that is the asthenosphere , which is spicy enough that its rock-and-roll are more flexible and tensile than those above it . The geosphere is divided into rough two twelve major and minor plate , and these plates move very lento over the almost fluid - the like asthenosphere .
There are two types of gall : oceanic impertinence and continental cheekiness . Predictably enough , pelagic crust reach up the ocean bed and are much thin than their continental counterparts . Plates can be made up of either oceanic or continental cheekiness , or just as often some combination of the two . There are a kind of force pushing and pulling the denture in various directions , and indeed that ’s what keep on Earth ’s crust from being one self-colored landmass – the interaction of lithosphere and asthenosphere celebrate tearing land mass apart , albeit very , very slowly .
When Plates Meet
The diagram below gives you a estimable idea of the different ways that plates can interact at the boundaries between them . There are convergent boundaries , in which two plates bang up into each other . Two potential things can happen here – either one home base err underneath the other and is subsume and destroyed in the furnace of Earth ’s drapery , or the two plate collide and force up huge mountain reach . These collisions are also often responsible for volcanism .
There can also be transform boundaries , where the two plates move in parallel , glint off of each other with not much more than some scrapes . Of course , those scrapes become something much more severe when translated to human terms – one of the most famous lesson of a transform limit is California ’s San Andreas fault , responsible for for some of the most devastating earthquakes in American history .
Finally , there are diverging boundaries , in which two plate skid away from each other . These are far more mild in their effects , and such limit have create places like Africa ’s Great Rift Valley and various giant ocean ridges like the Mid - Atlantic Ridge .
It ’s utterly crucial to remember that all of this happens fantastically slow , and that it takes many millions of years for any effects to be in reality observable . At their sheer quickest , plate only move about 160 millimetre per year , and most only go about 10 to 40 millimeters per year . To get some idea of how slow that really is , let your hair and fingernail grow uncut for an full class . Your fingernail growing represents the tiresome pace of plate movement , while your fuzz growth is the same as the absolute greatest space any shell has traveled in the last year .
Defining a Supercontinent
There are only so many way in which the various plate can move , and it ’s only a matter of time before the continents break together to constitute a single supercontinent . Right now , we ’re in all likelihood a short preceding halfway through the current supercontinent cycle per second , with the last supercontinent Pangaea having formed about 300 million year ago and the next supercontinent due in ( very ) roughly 250 million years .
We need to be careful with our terminology here . Continent itself is n’t a well - delineate term – just look at how nobody knows whether the continent in the south Pacific Ocean should be promise Australia or Oceania to see how knavish these thing are to set – and the condition supercontinent can be apply to any unco large landmass .
Indeed , the landmass consist of Europe , Asia , and Africa is definitely a supercontinent , the Americas arguably numerate as well , and we ’re one drown country bridge in the Bering Strait away from connect up all five anyway . So , for the sake of simpleness , we ’ll restrict the terminal figure “ supercontinent ” to only those that pretty much make up all the landmasses on Earth at a give period .
The Current Cycle
The most recent supercontinent , and the only one most citizenry are familiar with , is Pangaea , which dominated Earth from about 300 to 150 million year ago . There are a few fashion we know of its existence . There ’s the fact that species from this metre showed comparatively little diversity , no matter how far aside they were geographically , which indicates they were n’t isolate from one another by oceans .
The geology of various modern continents also argue how they used to be connect to each other . You only have to glance at a map to see how easterly South America and western Africa fit rather neatly together , and geological inquiry has expose these areas still share some key feature article that prove their one - meter link .
Pangaea gets remember because it ’s the most recent supercontinent , and because its former Clarence Shepard Day Jr. overlap with the birth of the dinosaur in the late Triassic and early Jurassic . Geologically speaking , it ’s easy to await at Pangaea as a opposite number of sorts to the seven continents we know on today , with the matching gargantuan continent of Gondwanaland and Laurasia as a transitional microscope stage between these two extreme . But it ’s generally block that Pangaea is just the later in a assembly line of about half a twelve supercontinents , and Earth will see quite a few more over its net five billion year of liveliness .
Back To The Beginning: Ur and Valbaara
terra firma ’s earliest days stay on somewhat mysterious – indeed , much of what we ’re discuss here is still being lick out by geologist , and so we have to make a lot of best guesses in undertake these topics . A complete account of how our satellite formed from bunch of outer space rock music into something even theoretically equal to of endorse aliveness is really deserving its own freestanding post . For our purposes , we can take up around four billion old age ago , when Earth ’s ocean were already in property and the first proto - continents began to form . During this period , shell construction block eff as cratons , which are basically jumbo rock and roll substance , started to hail together and rise to the surface .
There are a twosome candidate for the very first continents . There ’s some grounds that two craton day of the month back to as much as 3.5 billion age ago , make the tiny continent of Vaalbara . It ’s a supercontinent simply because it was all alone on our planet – any IE visiting Earth would have seen a single chocolate-brown acid against all the blue . Today , Vaalbara is spread between two cratons – the Kaapvaal craton in southern Africa and the Pilbara craton in northwestern Australia . We distrust Vaalbara ’s cosmos because rocks chuck out from these cratons are some of the old in the world , and there are a number of geologic clues that the two cratons were once together .
Still , Vaalbara ’s existence is still rather wondering , and so the more sure candidate for erstwhile supercontinent is Ur . Like its possible predecessor , Ur was modest than any of today ’s Continent , but it may well have spend many trillion of years as the only continent on our satellite , with nothing but some tiny islands to keep it company . Today , Ur lives on as part of India , Madagascar , and Australia .
While Vaalbara likely subsist from about 3.6 to 2.8 billion years ago , at which distributor point is cratons were broken aside , Ur organise just about 3 billion years ago and actually hold out in tact as part of expectant supercontinents until the break - up of Pangaea only 200 million years ago . At just under 3 billion years , Ur is almost certainly the longest - live landmass this satellite will ever see , and yet now it remain dispiritedly obscure .
Kenorland and the first Snowball Earth
Of naturally , continents that were just half the size of Australia ca n’t really be considered supercontinents by today ’s standards , but that was the macrocosm in which they live . The satellite was almost wholly sea at this phase angle in its story , and cratons were n’t push up from the mantlepiece all at once . We start to get a little closer with the emergence of Kenorland and Columbia , the next two supercontinents .
Kenorland make or so 2.7 billion yr ago , and it was considerably larger than Ur or Vaalbara , although still not gigantic . It comprised most of the modern US and Canada , Greenland , the Norse countries , western Australia , and what is now the Kalahari Desert , which stretches over much of southern Africa . Kenorland in all likelihood exist around the equator , and believably had about a hundred million years as the Earth ’s dominant landmass .
Geologists are still working out the accomplished account , and I offer just one interpretation of how we got to this point in time . Here ’s another look at the process from this rather rocking television by National Geographic :
It appears that Kenorland broke up around 2.6 billion years ago , creating a monumental spike in rain . This in tour caused a decrease of greenhouse petrol like carbon dioxide , which was n’t facilitate by the fact that the Sun itself was weaker then than it is now , at only about 85 % its present magnate . This created the first Snowball Earth , as the entire planet spent millions of old age at below freezing temperature . It would n’t be the last prison term a detachment of a supercontinent wreaked massive environmental consequence .
Columbia, Rodinia and Panottia
The first “ proper ” supercontinent was probably Columbia , which form around 1.8 billion years ago . Columbia had a earth mass of roughly 50 million square kilometers – still quite a mo less than our modern totality of about 150 million , but still pretty immense . From this point on , the picture asterisk to get a lot clearer , as we reach the first supercontinent that geologist are absolutely certain about .
Rodinia form about a billion years ago out of the long - break up remnants of Columbia , along with additional cratons and pieces of encrustation that had uprise up in the hundreds of millions of years . We do n’t know a mass about exactly what Rodinia looked like , but it was giving , was probably place almost entirely south of the equator , and began to break apart roughly 550 million years ago .
This separation was one of the most authoritative and cataclysmic events in our planet ’s chronicle . Like the separation of Kenorland , Rodinia ’s destruction make a Snowball Earth , but that was n’t all . Rodinia , like all the supercontinents before it , had been altogether destitute of life , as all being still lived in the oceans . The dissolution of Rodinia unfold up raw ocean and caused the ocean bed to rise up , creating shallower seas that offered the much - needed stepping stone for beast and works to make their manner onto land .
There were also more subtle issue . The breakup of Rodinia created monumental volcanic explosions , which likely shoot rich nutrient from beneath the Earth into the oceans . This made lifetime considerably gentle for being , first helping them weather the extremes of the Snowball Earth and then yield them the Energy Department cost increase needed to colonize earth . Without Rodinia , and for certain without collection plate tectonics , none of would be here today .
Three Possible Futures
Between Rodinia and Pangaea , there may have been one other supercontinent , which is known as Pannotia . Assuming it existed – and there ’s still disagreement on that detail – Pannotia was something of an accidental supercontinent , created by peek collisions between architectonic plates instead of any real yoke . The Pannotia supercontinent configuration was one born of coincidence and did n’t last long , break up just 60 million years later and giving means to Pangaea , last of Earth ’s supercontinents .
For the time being , at least . continent are still on the move , and they ’ll almost for sure carry on to move until the Sun vaporizes our planet in five billion twelvemonth ’ time . In all likelihood , the continents will merge again to form a new supercontinent within in the next 250 million years , fill out the up-to-the-minute act of the supercontinent cycle . This utterly amazing picture trace the movement of the continent through the end of Rodinia to the formation of Pangaea , and then on another 250 million years into our future :
As you could see , savour the Atlantic Ocean while you could , because it wo n’t be around forever . Africa and North America will ram into each other , while South America is start to get cozy with Antarctica . Australia will ram into China and southeast Asia , which really just sounds like the premiss for a mildly offensive sit - com . And Europe ? Poor Europe front like it ’s headed for significantly colder clime , acquire dangerously close to becoming the fresh North Pole .
This is one potential contour , although there are at least three scenarios that geologists consider realistic . All of them have pretty amazing names : Novopangaea , Amasia , and my personal favorite , Pangaea Ultima . The version we see up top , with the closure of the Atlantic , is Pangaea Ultima , whereas the Novopangaea and Amasia theoretical account holds that it ’s the Pacific that will close , making the Atlantic far bigger than any of today ’s oceans . Here are some creative person ’s conceptions of all three :
Pangaea Ultima is probably the somewhat preferred theory of geologists , but there the Pacific home plate does seem to be sliding underneath North America and Eurasia , which would mean the ocean itself with close if it continues on this present line . But that ’s the trouble – we ’re trying to forecast trillion of age worth of of incremental motion base on a pitifully incomplete dataset . A best guess is about the most we can really wait .
The Ever-Changing World
Plate tectonics has driven the story of our major planet . When all the continents were one , organisms moved freely and spread out across the satellite – dinosaurs might not have become the dominant species if they had n’t had Pangaea to give them absolute dominance of all land . When the continents spread , the closing off of dissimilar population induce a spike in genetic diversity that take crucial periods of evolution . It ’s unlikely that humanity could have ever made it if our ancestors ( and I ’m going back to our pre - primate root here ) had know exclusively on a supercontinent or stranded landmasses .
And , of course , climate is mold by the Earth ’s change over geology . Twice supercontinents have divide asunder to create devastating chain reactions ensue in the Snowball Earth . continent open up and coming together has both cool and warmed the planet in complex fundamental interaction that we ’re still puzzling out . Indeed , the saga of the supercontinents is still incomplete , and not just because we do n’t where it ’s headed . There ’s a lot about our own past that we still have to mold out .
But we already plausibly know the cool part about denture plate tectonic theory – it ’s the idea that the past times and future of our planet do n’t needfully look anything like the Earth we live on right on now . If you buzz off in a time simple machine and headed 250 million years in either direction , you ’d think you were looking at an alien planet , and our human beings is only going to look stranger and more unrecognisable the further into the past and future we go . So here ’s to the Pangaeas , both Classic and Ultima , the once and future supercontinents .
For more on this topic , check outPlate Tectonics : An Insider ’s History of the Modern Theory of the Earthby Naomi Oreskes andSupercontinent : Ten Billion Years in the Life of Our Planetby Ted Nield .
ColumbiaContinentsEarthGeologyPlate tectonicsScience
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