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Deep Future: The Next Supercontinent

Science fiction writers range freely through time, making many scientific papers fertile ground for plot ideas and settings. So here’s an extraordinary one. We know that Earth’s continents used to be packed into a single large land mass called Pangaea, which is thought to have broken apart about 200 million years ago as tectonic plates shifted. Interestingly, we can expect a remote future in which the continents will have once again come together, as Michael Way (NASA GSFC) has pointed out at an online poster session at the ongoing virtual meeting of the American Geophysical Union. And such a supercontinent has ramifications for habitability.

Let’s talk about those because they have a bearing on astrobiology as we examine exoplanets and consider their suitability for life. We’re a decade or so (at minimum) away from being able to determine how land and sea are distributed on a nearby world, but climate modeling is useful as we look toward estimating habitability. That involves, as this work shows, investigating how land masses are positioned on a planetary surface and their effects on climate in the habitable zone.

Working with Hannah Davies and Joao Duarte (University of Lisbon) and Mattias Green (Bangor University, Wales), Way has run 3D global climate models which are, according to Columbia University’s Earth Institute (where Way is an affiliate) the first models made on a supercontinent in the deep future. Out of this the scientists derive two likely outcomes. The first, occurring in the modeling in about 200 million years, is a merging of all continents except Antarctica around the north pole, forming the supercontinent ‘Amasia.’

The second: The formation of the supercontinent ‘Aurica,’ as all the continents come together around the equator in about 250 million years. The effects are significantly different. The formation of Amasia around the north pole produces a planet about 3 degrees Celsius cooler than the one resulting from the formation of Aurica around the equator. What happens is that the movement of heat from the equator to both poles is disrupted with all the land around the poles.

With heat not being conveyed as efficiently from equator to pole, the poles become colder and remain covered in ice all year long, reflecting significant heat into space. Amasia, according to Way, produces “a lot more snowfall. You get ice sheets, and you get this very effective ice-albedo feedback, which tends to lower the temperature of the planet.”

You also get lower sea levels in the Amasia scenario, with more water trapped in the ice caps. Less land is available for agriculture in a supercontinent with predominantly snowy conditions.

Image: How land could be distributed in the Aurica supercontinent (top) versus Amasia. The future land configurations are shown in gray, with modern-day outlines of the continents for comparison. Credit: Way et al. 2020.

Aurica turns out to be a more clement place, absorbing the stronger sunlight at the equator and, without ice caps at the poles to reflect heat, having a higher global temperature. The setting sounds like it would be ideal save for the fact that, according to the 3D models, the inland areas would be dry. What the scientists have not yet examined is the kind of precipitation patterns that might emerge. Large lakes would offset the effect, so it would be useful to know how likely they are.

All told, the work is pointing to temperatures suitable for liquid water on about 60 percent of Amasia’s land, while 99.8 percent of Aurica’s terrain should be available. We come back to land mass arrangements as a factor in planetary habitability, given our reliance on habitable zone models that insist on the presence of liquid water on the surface. Building a library of land mass distributions and examining their varying effects may help us tune our notions of habitability.

I’ll add that Way’s investigations using the GISS [Goddard Institute for Space Studies] General Circulation Model and expanding it to model paleo- and now future Earth have also extended to models of early Mars and Venus, with plans to examine Titan’s atmosphere. What our own planet has to teach us about climate, habitability and continental arrangement is thus extended to other worlds as the model evolves. One day soon we’ll add exoplanets into the mix.

The paper is Way et al., “Deep Future Climate on Earth: effects of tectonics, rotation rate, and insolation,” in process at Geophysical Research Letters (abstract).

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{ 24 comments… add one }
  • charlie December 2, 2020, 15:32

    It doesn’t matter what shape it will take in 50 billion years or so, we won’t be around to see it. By the by, what makes him think that these continents are even going to come together again?

    • Ron S. December 2, 2020, 18:49

      About your first sentence, as Paul said: “Let’s talk about those because they have a bearing on astrobiology as we examine exoplanets and consider their suitability for life.”

      In the second sentence, are you claiming that the paper doesn’t support these projections for plate tectonics?

    • Alex Tolley December 2, 2020, 19:11

      The plate positions can be predicted to some extent by the relative rates of spreading and subduction. The paper states that super continents appear on a cycle. The 2 scenarios are based on other papers.

  • Gary Wilson December 2, 2020, 16:06

    ????. Don’t follow your reasoning Charlie. You know about the movement of the earth’s tectonic plates right? I believe the Atlantic is shrinking by about 2 inches per year and the Pacific region is growing by about the same due to the movement of the plates. The numbers for new supercontinents forming are in the hundreds of millions of years and would seem to make sense. It has happened before and it will happen again.

    • Bruce D Mayfield December 3, 2020, 15:01

      I didn’t follow charlie’s reasoning either Gary. 20 billion years is >> the 200 million year projections of the paper, but perhaps his point is that any time way passed ours is irrelevant? If that’s what he meant then it is a somewhat narrow minded viewpoint.

      On the point you make about the oceans it is the Atlantic that is currently widening while the Pacific shrinks. However it is expected (?) that the expansion of the Atlantic will reverse at some point (why?) and that the next supercontinent will form from the closure of the Atlantic. (with Africa and Australia having already followed India’s collision with Eurasia)

      Questions re this projection: Did they take into account the expected increase in solar input from our aging Sun? It’s been estimated by some that in only 1 billion years it will be too hot for liquid water on Earth and our oceans will have boiled off. In 1/5 of this time will Earth still be able to have massive ice ages, even with most land near the poles?

      • Bruce D Mayfield December 4, 2020, 13:44

        Yes, (answering my own question) the paper did factor in solar change. As a fan of pleistocene megafauna it is cool to be able to expect ice ages far into Earth’s distant future.

        My take from this as far as prospects for habitable exoplanets go is just how durable not just habitability, but clement inhabitability for lifeforms like us can be on sufficiently Earth-like worlds. If a planet or moon has the right mass, core dynamo, crustal thickness, H2O content and distance from a long lived star it can be, not just barely habitable, but very habitable for an extremely long duration.

  • Alex Tolley December 2, 2020, 19:24

    Habitability is one issue, but as a biologist it is biodiversity that generates more forms and ecologies. The separation of continents, as well as islands generates separate and interesting evolutionary paths. Humans emerged from the old world primates and migrated to the other continents by various means. Even the the Central American land bridge when it appeared resulted in changes in the S. American fauna as the N American mammals outcompeted the S American marsupials. There is also the famous Wallace line that senates very different species across a narrow distance of ocean in the Pacific.

    The position of the continents will affect biodiversity too. A super continent over the N Pole if cooler will have fewer species than one positioned over the equator where warmth and rainfall may produce tropical forests with high biodiversity.

    I don’t know the details of the GISS model used, but does it take into account ocean currents that emerge depending on the spatial posioning of land masses and their impact on climate?

    • Alex Tolley December 2, 2020, 22:46

      The paper does indicate that ocean circulation is modeled.

      The authors indicate that several variables are not able to be modeled, such as CO2 changes with volcanism and uncertain weathering.

      No suggestion of the impact on biodiversity is made. The authors simply note that in the Pangea period, ocean diversity was not obviously different than with other periods, although this says nothing about terrestrial organisms.

    • Andrei December 3, 2020, 15:31

      Absolutely correct, and while continental drift and sequestrating CO2 both are necessary part for maintaining a biosphere. Besides those land bridges, we also got the ice ages that might have pushed our species in the direction we now find ourselves in. This since changes in the environment push evolution forward. In the end we must ask what made our planet special so complex life and equally complex ecologies can be found here. As Earth is the only terrestrial planet with a moon, it have long been suspected it had something to do with complex life. But not exactly in which way, if there is for the tides – or even that it have stabilized the rotation of Earth. But now as Change 5 is bringing lunar samples back to Earth from one area that might have been changed by surprisingly late volcanism, we find that the magnetic field of the Moon might have made an important contribution in making Earth a living planet. If this and perhaps all three is required from a large satellite – we might be on the path to an answer why terrestrial planets with life is so unusual, and why just the right size, age and distance from the primary is not enough to immediately jumpstart a stellar faring civilisation.
      https://www.newscientist.com/article/2257286-the-moon-had-a-magnetic-field-that-helped-protect-earths-atmosphere/

      • Bruce D Mayfield December 4, 2020, 4:43

        Fascinating article Andrei. Yet another benefit from our large satellite and the collision(s) that formed it. (This tips the judgement scale at least a little more toward Rare Earth, doesn’t it?)

        • Andrei December 8, 2020, 17:44

          Thank you Bruce.
          I would say it does tip the scale further. Though I have had to admit that I held this view even before the term existed or planets in other systems were known. But the hypothesis then was that planets is a natural part of stellar formation. Add to this that as a student I was the member of the science club and we for fun calculated that interstellar flight actually would be possible with fusion (Our design had 3 stages and could decelerate at the target star Alpha Centauri. Some year back I actually considered sending our small amateurish study to Cheungs atomic rockets . But I found several errors.) This was one or two years before project Daedalus, the idea might have come from Poul Anderson’s Tau Zero which had been translated.
          When a technological society able to fly to the stars, we ended up with the question of why the universe would not be filled with spacefarers already. Especially since any civilization could have had a billion year headstart on us humans.
          At about that point someone of us pointed out there already were something called Fermi’s Paradox and we had a laugh that we ended up with the same line of thought as a famous scientist. But my professional life took another path than spaceflight and astronomy, as the other grand interests biology was more close at hand. Even now near the end of my career I still spend time reading up on papers in those fields, and still try to find the reason for how and why Earth ended up as the very rare jewel it is. Now everyone out there take care, even though we might see the beginning of the end of this COVID-19 mess, it’s not over yet – and Happy new year and Christmas to everyone!

    • Robin Datta December 6, 2020, 22:30

      Valid comment, all.
      “N American mammals outcompeted the S American marsupials”
      N American eutherians/placentals outcompeted the S American marsupials?

      • Bruce D Mayfield December 8, 2020, 14:24

        Except for possums y’all, or as northerners call ’em O’possums. Texas even has a state park named Possum Kingdom.

  • laintal December 2, 2020, 20:37

    Hi

    Yes this sure was interesting, I hope the paper has better maps of the climate zones and floral zones

    Cheers

  • Michael December 3, 2020, 17:50

    Interestingly a polar gathering would have less effect on slowing the earths spin versus a equatorial gathering due to tidal dissipation having more resistance at the equator.

  • Thomas W Hair December 4, 2020, 12:42

    In the Ward and Brownlee books “Rare Earth” and “The Life and Death of Planet Earth” the authors correctly point out that we live in the middle of an unique and short window of time beginning with the great oxidation resulting in the Cambrian Explosion and the future ultimate demise of all eukaryotic life on this planet due to the Sun’s increasing temperature. 250 million years from now the Earth will be uninhabitable. We are separated in both time and space by entire geologic epochs and thousands, if not millions or billions, of light-years. If they exist at all and are within this galaxy, they are very ancient, they keep to themselves, and they can make a reasonable assumption, even from 25,000 light-years away, that we are in existence or could be using imaging technology we cannot fathom.
    https://www.fgcu.edu/directory/twhair?list=1

  • Spaceman December 4, 2020, 17:35

    Deep time is a fascinating topic! When I think about the far future discussed in the Way et al paper, several questions come to mind. Interestingly, the timescales discussed in this research are on par with a “galactic year” which is defined as the time it take for our solar system to orbit once around the center of the Milk Way and has been estimated to be between 225 and 250 million terrestrial years.

    1). What multicellular lifeforms will exist when the continents reassemble into a new supercontinent?

    2). How likely is it that humans will still be present on Earth in ~250 million years? If humans are not present on Earth in this distant future, will it be because humans went extinct in the interim, or, is it because humans left earth for elsewhere? If humanity goes extinct before another galactic year passes, what are the most likely culprits (I know Paul is currently reading Toby Ord’s book “The Precipice”)?

    3). Will another intelligent species have evolved on the planet in one galactic year? If so, would this new intelligent species– assuming that it is scientifically inquisitive– be able to detect remnants of human civilization left over from our time? Or, would all traces of technological civilization from our time be undetectable from background noise by then?

    4). If humans abandoned Earth before one galactic year, will they have established themselves in just the solar system, or, will the species have gone interstellar or even intergalactic?

  • Spaceman December 4, 2020, 18:39

    Hi Thomas,

    As a deep time aficionado, I read and enjoyed both of those books you mentioned by Ward :-) You mentioned that Earth will be uninhabitable in 250 millions years. I thought the habitability window for multicellular life was more in the range of 500 million years to 1 billion years?

    • Thomas W Hair December 5, 2020, 12:36

      You are absolutely correct, though that multicellular life won’t be of the large mammalian animal variety. By 250Myr it’ll be all cock roaches and stromatolites.

  • Sara December 5, 2020, 13:41

    Not criticising, but just wondering why the speculation did not take into account the rift zone in Antarctica? It starts well north of the Straits of Boxporus, runs all the way south down through Ethiopia and the Danakil Depression, down through the east African rift zone and from there south to Antarctica. The active volcano Mt. Erebus sits on it, as does Kilimanjaro.
    I don’t have an issue with the speculation, just wondering why that was left out, because it is important and it is active now.

  • xcalibur December 5, 2020, 23:14

    Interesting theoretical stuff. As a species, we tend to be a bit short-sighted — it’s a useful exercise to think in the very long-term, beyond our natural lifespan, which relates to this research. Ultimately, long-term survival means space colonization, and mastering the complex forces around us. Perhaps in the far future, we’ll be able to secure the Earth against eventual sterilization/destruction by the Sun’s evolution, and seed our biosphere far and wide.

  • Robin Datta December 7, 2020, 0:05

    In the perspective of evoution from hominins to humans the acceleration of human evolution might suggest (a/the) subsequent species quite different from “us”. That even here on earth, and more so on colonizers on travellers (as on generation ships) elsewhere. From their perspective, Homo sapiens sapiens might be extinct, just as we consider Homo erectus to be extinct.

    A oxygen-carrier to supply the brain and a transport system to get it there will be needed if oxygen plays its present role. This excludes present invertebrates.

    For another lineage to evolve comparable intelligence, it would need sufficient partial pressure of oxygen to maintain a high rate of oxygenation of the blood to sustain a large brain. This would need a gas-liquid exchange (lungs) rather that a liquid-liquid exchange (gills). This excludes pisces.

    A high rate of brain metabolic activity would need a steady warm core body temperature (homeotherms) rather than a temperature that varies with the ambient conditions (poikilotherms). This excludes amphibia and present reptilia.

    Three axes for shoulder movement by brachiation, overlapping fields of vision providing binocular vision (to judge the distance to the next tree branch, later to make tools and weapons and to wield and throw weapons). Highly specialized forelimbs exclude aves and several (most?) mammalian orders.

    Next would be a forest with a continuous canopy to permit brachiation. And an appropriate environment to promote bipedalism including a transition from forest to grasslands. This frees the upper extremity from locomotion for the use of tools and weapons. Control of fire permits cooking and reduces the need for mastication and the size of the teeth. This alters the upper airway, which together with upper airway alterations from upright posture permit vocal modulation needed for speech.

    A fairly tall order for another intelligent species along the same pathway.

  • Mike Serfas December 13, 2020, 21:36

    Speaking of history on a geologic scale … I wish there were a way to riddle out what stars had passed how near to the Sun. A very limited diagram like https://en.wikipedia.org/wiki/File:Near-stars-past-future-en.svg gives a rough idea that the Sun might have a different ‘nearest neighbor’ every 20000 years or so, and if I compare that to the list of brightest stars at http://www.atlasoftheuniverse.com/50lys.html it suggests that a few of our nearest neighbors in any 28-million-year period will be nearly five orders of magnitude brighter than Alpha Centauri, perhaps even rivalling Venus. But has anything more extreme appeared in the sky? When I think of how readily humans (and their pets) sleep with the little power lights of machinery in the background, and the relative resilience ecosystems have shown to high levels of light pollution, I suspect the planet must have had to accommodate itself to something remarkable in fairly recent geologic time.

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