The ground is moving.
It's a creeping movement, but a momentous one. Some 200 million years ago, a single, extraordinary supercontinent called Pangea dominated Earth. Ultimately, landmasses ruptured and pulled apart, creating the world we see today. Yet the continents never ceased drifting. And in some 250 million years' time, computer simulations suggest that a supercontinent may again prevail.
"It might end up looking a lot like Pangea did when the dinosaurs were roaming around," Hannah Davies, a geologist at the GFZ German Research Centre for Geosciences who researches future continental change, told Mashable.
While it's certain the continents have migrated and continue to migrate — owing to a preponderance of evidence from rocks, fossils, the fit and shape of our continents, and beyond — it's still uncertain how, exactly, such massive geological change will play out in the distant future. Yet visualizations made possible with modern computing have given scientists an improved view of our planet's geologic future. As we learn more about the behavior of Earth's tectonic plates (upon which continents move) and how our planet evolved in the past, these models will become better refined, Davies emphasized. (Other types of earth science modeling, like climate modeling, have proven remarkably accurate.)
"I have no doubt that we'll see another supercontinent," Damian Nance, a distinguished professor emeritus of geology from Ohio University, told Mashable. "I have a lot of questions about when that might happen and what that might look like. The jury is still out."
"I have no doubt that we'll see another supercontinent."
There are currently around four leading candidate ideas for the next, distant supercontinent. The animation below, created using software that constructs and visualizes geologic activity on Earth, shows a supercontinent, dubbed "Aurica," forming near Earth's equator. The Pacific Ocean closes, and eventually the Atlantic does too. (Some online platforms might not display the video below; if so, here's a YouTube version.)
In another supercontinent scenario called "Amasia," today's continents drift northward, except for Antarctica, and amass around the North Pole. Under a different geologic regime called "Novopangea," wherein the continents largely continue moving as they are today, the Atlantic Ocean continues to spread apart, but the sprawling Pacific closes. A fourth leading supercontinent candidate is the tropical "Pangea Ultima," wherein continents form around an Atlantic that stops spreading apart. Last year, a group of scientists used a supercomputer to model the climate on a supercontinent like Pangea Ultima, and found it would host inhospitable surface environs (owing to a surge in volcanism, heat in the tropics, and lack of marine cooling in the sweltering interior). Without evolving, many species likely couldn't survive on much of the scorching surface.
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Millions of years ago, Pangea's vast equatorial interior was also likely a dry, arid landscape, and hosted expansive deserts. "The interior of a supercontinent would be pretty horrific," Nance noted. This almost certainly posed challenges and evolutionary pressures for ancient life; yet even so, those harsh conditions saw huge biological successes: Some life that began developing on Pangea would later come to dominate Earth. "You can think of Pangea as being both the cradle of dinosaurs and mammals," Nance marveled.
The next supercontinent — be it Aurica, Amasia, Novopangea, or Pangea Ultima — probably won't be Earth's last. The continents glide over Earth's heated mantle, a thick region of semi-solid rock, which convects (somewhat like hot wax circulating in a lava lamp) and moves the continents above. "The driving force is mantle circulation," Nance explained. Geologists don't expect this process to stop for a long, long time. In fact, the continents are likely in a slow-motion supercontinent cycle — with massive landmasses repeatedly converging, breaking apart, and converging once again.
"We could end up with six or seven supercontinent cycles throughout Earth's history," Davies explained, noting the planet may have already had four or five supercontinents.
Nance suspects geologists are getting tantalizingly close to solving some of the big uncertainties, which lie hundreds to thousands of miles below in the mantle, that will drive the future direction of the continents. For example, continents tend to move away from areas where hot rock is welling up in the mantle — similar to how a potato in boiling soup will move away from the hottest boil. Crucially, knowing how these deep geologic phenomena behave won't simply help predict the next supercontinent. "Ultimately, it's enormously important," Nance emphasized. "It tells us how Earth works."
A question that looms large is, when the continents next collide into a great mass, surrounded by an even greater sea, who will be around to witness it? Human civilizations, born with the rise of agriculture, have only existed for some 12,000 years. It's difficult to envision the next decade, if not the next century.
"We could end up with six or seven supercontinent cycles throughout Earth's history."
Might humans be around to inhabit a supercontinent in some 200 or 250 million years? "That would be a grand old age for a species," Nance marveled. It would mean existing for much longer than the dinosaurs, which went extinct after 165 million years. Yet after deflecting a number of giant, menacing asteroids and avoiding self-annihilation, it's possible. But species evolve.
"The sheer timeframes involved boggles the mind a little bit," Davies mused. "There's definitely a chance we'll be around in 250 million years, but we'll be quite different."
