why scientists worry the next pangea could mean the end of life on earth
Researchers trying to model what our planet will be like in 250 million years have some very bad news for us.
Imagine our planet with just one giant ocean and a single, vast landmass. It’s not just a thought exercise. Every 500 million years Earth ends up with a supercontinent which has one global ocean surrounding it since the emergence of Vaalbara some 3.6 billion years ago. Our last supercontinent was Pangea, which very famously broke up during the heyday of the dinosaurs and gave birth to the Atlantic Ocean. And the very same forces which created and destroyed Pangea are still in motion. In another 250 million years, most of our current landmasses are set to collide in the middle of what is now the Pacific Ocean and fuse into the next supercontinent: Pangea Ultima.
But while this is great news for symmetry enthusiasts, it may actually be horrible news for life. You see, when Pangea was created, it caused the worst mass extinction in the fossil record as volcanoes and massive lava beds went into overdrive and turned Earth into a furnace over the course of 10,000 years. Global temperatures regularly reached 50 °C as vast swaths of the inner continent turned into harsh, arid deserts flanked by sun-baked mountains. Marine ecosystems virtually collapsed. Starvation and volcanic eruptions would end up killing almost 90% of all species. As geology settled and new species emerged, they found seemingly endless wastelands.
Yet, as bad as the Permian Extinction was, supercomputer models are predicting that Pangea Ultima will be even worse, ushering in a Second Great Dying. Why? Well, there will be two major factors in play. The first is that colliding continents will create major seismic events that fuel volcanic activity and excite enormous hot spots and magma plumes which could trigger millennia-long eruptions like the Siberian Traps during the Permian. The second is that as the Sun ages, it will become hotter as its core fills with more helium, increasing in density, and fusing hydrogen faster. Over time spans like a quarter of a billion years, that adds up to 2.5% more heat and light.
Add it all up and you end up with a world which resembles Arrakis from Dune, where typical days routinely see highs between 40 °C and 70 °C, and water would flow in underground wells and aquifers deep under the surface. In this climate, some 92% of living mammal species would be quickly driven into extinction. Even humans would find it difficult to survive in such harsh conditions, so much so, the researchers behind the models suggest that if our species is still around in some form, we should look for another planet to call home as we’d end up having to spend our days living in artificial environments sprawling through underground chambers and tunnels.
Or, at least, that’s what the pop sci headlines say. Reality would be a lot stranger since we’re now talking about timescales beyond normal human comprehension, ones that allow for all sorts of seemingly unlikely and bizarre things to happen. Mammals might be extinct for many of millions of years before Pangea Ultima even starts to assemble, unable to cope with brutal selective pressures of eons with looming ice ages, asteroid impacts, tropical hothouses, and other mass extinctions. Humanity will also adapt and change, and could be almost unrecognizable to us in just a few million years, radiating into numerous hominid species, if not merging with machinery to adopt alien forms.
Likewise, the models predict carbon dioxide levels 250 million years from now will be over 840 ppm, roughly twice those of today. But unlike today, when industrial activity raised them from 278 ppm to 412 ppm in just 223 years despite literally centuries of warnings, it could take a few million years to crank them up as high as predicted over the age of Pangea Ultima, giving life a chance to adapt. The end result won’t feature almost any of the species we know today or their relatives, and what biosphere is left will be a pale shadow of what once was, retreating to caves and the deep ocean for relief from the blazing heat and arid plains and mountain ranges.
Earth will be too hot for life at some point. After all, once typical temperatures start to reach the boiling point often enough, there may not be enough water to sustain much past extremophile bacteria, and even the deepest aquifers will eventually run dry. The Sun will continue building up helium in its core and getting hotter and hotter. After the breakup of Pangea Ultima, there may only be one more supercontinent like it before the planet becomes too hot even for microbes and oceans begin to evaporate under the burning light of our parent star. But that’s a billion years from now. Until that point, there’s still a very good chance something will call an Arrakis-like Earth home.
See: Farnsworth, A., et al. (2023) Climate extremes likely to drive land mammal extinction during next supercontinent assembly. Nat Geosci DOI: 10.1038/s41561-023-01259-3