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Wednesday, May 22, 2024

The Future Is Bleak. Pondering Pangaea Gives Me Hope

The human passion for gouging burnable stuff out of the earth and reducing it to ashes may well be the end of us. But it's not clear who the “us” is. Not you and me, obviously; we'll be lucky to see 2100. But “us” can't just mean our direct descendants, right? Does it have to mean hominids? Maybe humans of the far, far future don't even have to have blood or DNA to count as survivors. Hundreds of millions of years from now, we primates could live on in our component parts: oxygen, carbon, hydrogen, and nitrogen. We could have a kind of immortality of the elements.


Unlike the imperiled biosphere, Earth's crust and mantle, which are charged with many of the baseline ingredients of humans, show no signs of decline. In fact, they're having a heyday—erupting, grinding, migrating, and splintering in unpredictable ways. Recent data also indicates the plates are up to something supremely weird: making a discreet move toward reunification. Like gazing at the stars, contemplating the so-called deep future of Earth with a new supercontinent can take the sting out of bleak climate predictions for the nearer term.

In about 200 million years, our far-flung continents may join up again. Though progress toward the Pangaea Proxima, the next Pangaea, is slow, it is also measurable. Seismologists have found that the Mid-Atlantic Ridge, a mountain range on the ocean floor that separates North America from Europe and Africa, is expanding about as fast as fingernails grow, broadening the Atlantic Ocean at a rate of some 4 centimeters per year. Meanwhile, the Nazca, a plate off the west coast of Peru, seems to be moving faster, about the speed that hair grows, which may be closing up the Pacific.

Of course, the chance that humans will exist to check the prediction is essentially zero. But to study the deep future is to recognize that flora and fauna, human fauna included, may be bit players in the fathomless intergalactic drama of chemicals.

Eons in advance, then, cartographers and earth scientists are clocking continental drift and fantasizing about new worlds. “Amasia” is the name for a hypothetical supercontinent formed when Asia, Africa, North America, South America, Europe, and Australia all fuse around the north pole. An even deeper-future hypothesis, which might take 250 million years, is called “Aurica,” the coalescence of all seven continents, including Antarctica, around the equator. It will no doubt be useful that the next Pangaeae are named in advance, so the rocks will have something to call themselves.

This past January, British seismologists based at the University of Southampton on England's south coast—Southampton was the illustrious departure port for the Mayflower and the RMS Titanic (so they care about geological oceanography)—found new ways to observe mantle convection, some 400 miles below Earth's crust and more than a thousand miles from its core. The material there is surging. As plates move apart along the Mid-Atlantic Ridge, material rises to fill the space between them. As the team reported in a paper published in Nature, these surges could shove tectonic plates up from below and help push the continents farther apart (meaning, since this is a sphere we're talking about, closer together around the back).

Nicholas Harmon, the lead scientist, succumbed admirably to dad-joke temptation when he announced these findings: “There is a growing distance between North America and Europe, and it is not driven by political or philosophical differences,” he said in a press release. “It is caused by mantle convection!”

And while this convection is brewing, the tip-top of the blue planet is also shifting uneasily. In the past few years, academic geomagnetists who oversee the World Magnetic Model, which maps the Earth's magnetic field and makes possible all navigation from Google Maps to naval systems, have noticed significant mapping errors. It seems that liquid iron sloshing around in Earth's core has driven the north magnetic pole away from Canada and put it on a collision course with Siberia. The speed of this polar migration has increased from 9 miles per year to 34 miles per year during the past two decades. The north pole. Moving fast. (A question for political science: Does this mean polarization is increasing or decreasing?)

Plate tectonics is one of the most romantic theories in all of science. Because it incorporates both revelations and hard data, and because its proponents, notably the illustrious American geologist and ocean cartographer Marie Tharp, faced cruel rejection by scientists followed by warm embrace, the theory is often used to exemplify how ideas evolve. It's built on an insight from the so-called golden age of Netherlandish cartography—unforgettable—when mapmaker Abraham Ortelius of the Low Countries spotted the continents' resemblance to pottery shards. The Americas, he wrote in Thesaurus Geographicus in the late 16th century, were “torn away from Europe and Africa … by earthquakes and floods.”


In 1912, Alfred Wegener, a dashing German meteorologist and record-setting balloonist, concurred, and further suggested that the landmasses once composed a supercontinent, which broke into pieces that drifted apart. E unus pluribum. To close his case for what he called “continental displacement,” Wegener referred to matching fossils of plants and animals on opposite sides of the Atlantic. He also cut up maps, fit the pieces together, and named the assemblage Pangaea. His insight was savaged as the rantings of a madman. It is now considered patently true.

From Wegener's time until into the 1960s, earth scientists extended Wegener's apprehensions to describe plate tectonics, the motion of the massive components of the Earth's crust and upper mantle—its lithosphere. While deeper spheres have greater plasticity, the lithosphere responds to stress by deforming either elastically or through brittle failure. Stress deforms and breaks the planet, and produces mountains, volcanoes, and earthquakes.

Perhaps plate tectonics is such a poignant idea because it reminds us that the whole glorious and dangerous topography of the Earth is determined by stress, collisions, upwellings, and ruptures. We're right to dwell on the biosphere, because we dwell in it, and it's us. But we also owe our existence to the dynamism under our feet. In the cracking, surging lithosphere, after all, are the primordial ooze, stones, clay, and ashes we're made of—our chemical kin, to whom the planet has belonged all along.

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This article appears in the October issue. Subscribe now.

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