What Will Earth Be Like 300 Million Years From Now?

We spend a lot of time here on Eons  looking backwards into deep time,   visiting ancient chapters of our planet’s history.

But this time, we’re taking a  look towards the deep future.

After all, the story is far from over.

The forces that have shaped the world into  what it is today haven’t stopped – and they’ll   continue shaping the planet for thousands,  millions, and billions of years to come.

And as we’ve improved our understanding of how  those forces work by studying the geologic past,   we’ve become the first species in history  that can predict global changes ahead of time… Allowing us to glimpse future Earths that  we humans may not even be around to see… Worlds with different ecosystems,   different climates, and even different  continents from the ones we know today.

And worlds that may or may not come to pass,   depending on what we do in this  chapter of the planet’s history.

Here’s what’s coming up next on Planet Earth.

Planetary-scale changes usually  unfold over extremely long time   frames - often millions or billions of years  spanning geological ages, epochs, and eons.

But if we begin by looking just 10,000 years ahead   into the planet’s future - a blink of an eye  in geologic time - what might have changed?

Well, that depends a lot on how  the next century or two goes.

If we keep releasing trillions of tons of carbon  emissions into the atmosphere this century,   the effects may still be impacting  the planet 10,000 years from now.

In one major 2016 study, for example,  a team of climate scientists calculated   four different emissions scenarios and modeled  their long term effects thousands of years out.

In the highest emission scenario, the  world warms around 7.5 degrees Celsius   over the next few centuries and stays  that hot 10,000 years in the future.

In this potential future world, we humans  essentially recreate the Eocene epoch – the   span of time between 56 and 34 million years  ago, the last time the planet was so warm.

The melting of almost all the land ice  from both Antarctica and Greenland raises   sea levels around 50 meters over  the next several thousand years.

This reshapes global coastlines and  swallows up many low-lying areas,   like, for example, most of Florida.

And the effects of this rapid warming  on the species of future Earth?

We can predict that, too.

See, ecosystems have been  affected by abrupt warming before.

Around 56 million years ago, at the beginning of  the Eocene, temperatures also rose between 5 and   8 degrees Celsius in under 10,000 years, making  it a useful comparison to our modern warming.

This was the start of the  Paleocene - Eocene thermal maximum,   an event that lasted around 200,000 years.

It was probably triggered by sudden bursts   of greenhouse gasses released into  the atmosphere from natural sources.

And the fossil record of many  species from before and after   this rapid warming shows a clear pattern -  one that’s also a warning for the future… Sudden warming shrinks mammals.

The teeth of Sifrhippus, the earliest horse,  for example, show that this already pretty   small species shrank by around 30% over  the first 130,000 years of the event.

At their smallest, they dropped to around  just 3.9 kilograms - about the size of a   house cat - before rebounding in size and growing  by over 75% when the planet cooled back down.

And researchers think that this  reversible dwarfing happened at   least partly because it increased  their surface area to volume ratio.

See, smaller bodies release heat more quickly,   which is useful for warm-blooded mammals that  have to tightly regulate their body temperatures.

So it’s possible that, in a much warmer  future world, the descendents of today's   mammals will shrink too, beating the  heat by becoming better at radiating it.

It might also give us another  Titanoboa, but that’s a different story… And while that world 10,000 years from  now depends on decisions we make today,   some changes in Earth’s more distant future have  been brewing since long before we were around….

Like, 10 million years from now, an  entire continent may split itself apart.

This is the possible end result of  the modern world's biggest active   continental rift: the Eastern African Rift system.

It snakes thousands of miles down the  eastern side of the African continent,   splitting the Nubian plate from the Somalian  plate and slowly pulling them apart.

The rift probably formed somewhere  between 30 and 40 million years ago,   possibly driven by superheated plumes in the  partially-molten mantle layer rising upwards.

These plumes cause the lithosphere above - the   planet’s solid outer shell  - to stretch and fracture.

At the current rate, the rift is pulling the   continent apart at just 7  millimeters a year or so.

But in about 10 million years,  if it doesn't slow down,   then even this snail’s pace may be  enough to split the continent in two.

Eventually, a new ocean will form as water floods  into the basin that opens between the two sides,   creating a huge new eastern African island  separated from the rest of the continent.

And, as we’ve seen many times before,  evolution gets pretty weird on islands.

From dodos to dwarf mammoths to gorilla-sized  lemurs, islands are evolutionary hotspots,   where isolation and unique  conditions breed innovation.

So 10 million years from now, newly-isolated  species that find themselves on this ‘Madagascar   2.0’ may suddenly diverge from their  mainland cousins in all sorts of ways.

But there is another possible future.

Instead of splitting the continent in two,   the rift system might just fizzle  out, as others have before.

Like the Midcontinent Rift of North  America, for example, which was on the   brink of cracking that continent down the  middle a little over a billion years ago.

But its activity stopped  shortly before that happened,   becoming the biggest known failed rift  that still scars the surface of the planet.

Whether the rift in eastern Africa will also  fail, or whether it will lead to the first major   continental break up in 30 million years, we’ll  have to wait 10 million years or so to find out.

When it comes to plate tectonics though,  big breakups are only ever temporary… And the next stop on our tour of the geological  future takes us forward nearly 300 million years,   to a world where the continents come back  together for the first time since Pangea.

See, one of the longest-term cycles that the   planet goes through over time  is the supercontinent cycle.

This squishing together of most of the  continents happens every 600 million years or so,   forming supercontinents that then break up again.

The last one, Pangea, formed around 320 million   years ago and it broke up around  170 to 180 million years ago.

And in 2022, researchers modeling  the future of this cycle were able   to predict how and when the next one might form.

They carried out supercomputer simulations to   model the movement of Earth’s tectonic  plates over extremely long timescales.

And the most likely scenario they saw was that,   somewhere between 200 and 300  million years into the future,   the planet will get a new supercontinent  which has already been dubbed Amasia.

The name comes from the pieces that will form  it - the collision of Australia, Asia, and  the Americas, closing up the Pacific Ocean.

It’s a process that is  slowly happening as we speak,   with the Pacific shrinking by  a few centimeters or so a year.

In a future world 300 million years from  now, it will potentially cease to exist   as the various landmasses it currently  separates finally come together again.

And while Amasia is just the latest  model, what the formation of any   supercontinent will mean for those future  ecosystems, well, that’s harder to say.

We’re closer in time to the earliest  dinosaurs than we are to any of those species.

The early dinosaurs got their start on Pangea  probably a little over 230 million years ago,   with bipedal carnivores like Herrerasaurus.

And they eventually radiated into  all kinds of diverse, strange,   and awesome species that flourished on  land for the rest of the Mesozoic Era.

So while we can model what the continents  might look like in the deep future,   what the species of that time will look like  is something no supercomputer can predict.

But we can say that, whatever lifeforms  call that future supercontinent home in   300 million years, many of them will  face a major ecological challenge… Because the new supercontinent’s vast  interior will become extremely hot and dry,   forcing species to once again adapt to  radically changing environmental conditions.

Although there are still unknowns surrounding  the question of what’s next for Earth,   looking into the past is a valuable tool  that allows us to also glimpse the future.

Because the planet is constantly changing,   and while it’s tempting to think of  the present as some sort of end point,   Earth’s story is still unfolding, and  there are many chapters still to come.