Just before the dawn of the dinosaurs — roughly 251 million years ago — Earth's continents abutted one another, merging to form the supercontinent Pangea. That land mass, which straddled the equator like an ancient Pac-Man, eventually split into Gondwana in the south and Laurasia in the north.
From there, Gondwana and Laurasia separated into the seven continents that we know today. But the constant movement of Earth's tectonic plates raises a question: Will there ever be another supercontinent like Pangea?
The answer is yes. Pangea wasn't the first supercontinent to form during Earth's 4.5-billion-year geologic history, and it won't be the last. [What Is Plate Tectonics?]
"That's the one part of the debate that there isn't much debate over," Ross Mitchell, a geologist at Curtin University in Perth, Australia, told Live Science. "But what 'the next Pangea' will look like … that's where opinions diverge."
Geologists agree that there is a well-established, fairly regular cycle of supercontinent formation. It's happened three times in the past. The first one was Nuna (also called Columbia), which existed from about 1.8 billion to 1.3 billion years ago. Next came Rodinia, which dominated the planet between 1.2 billion and 750 million years ago. So, there's no reason to think that another supercontinent won't form in the future, Mitchell said.
The convergence and spreading of continents are tied to movements of tectonic plates. The Earth's crust is divided into nine major plates that glide over the mantle, the liquid layer that sits between the core and the semi-solid crust. In a process called convection, hotter material rises from near the Earth's core toward the surface, while colder mantle rock sinks. The rising and falling of mantle material either spreads plates apart, or forces them together by pushing one under another.
Scientists can track tectonic plate movements using GPS instruments. But in order to piece together what these plates were up to millions of years ago, paleogeologists have to turn to natural magnets in the Earth's crust. As hot lava cools at the junction where two plates are colliding, some rocks in the lava containing magnetic minerals, such as magnetite, align with Earth's current magnetic fields. As the then-cooled rock moves via plate tectonics, scientists can use that alignment to calculate where, in terms of latitude, those magnets were located in the past.
According to Mitchell, a new supercontinent forms every 600 million years or so, but that cycle might be speeding up. This suggests that the next Pangea, dubbed Amasia (or Pangea Proxima) would form sooner than we expect. Mitchell thinks the cycle is speeding up because the Earth’s internal heat — hoarded in the planet's core since the time of its formation — is dissipating, meaning that convection is happening faster.
"Given that the heyday of Pangea was probably 300 million years ago, Amasia's would be 300 million years from now," Mitchell said. "But it could form as soon as 200 million years from now."
However, predicting the birth year of Amasia isn't so simple.
"The difficult thing about predicting the Pangea of the future is that you can't take present-day plate motions and hit fast-forward," Mitchell said. Plate motions can change unexpectedly, with imperfections in the seafloor causing plates to veer from their trajectories.
Presently, California and eastern Asia are converging toward Hawaii, while North America is moving farther and farther away from Europe, Matthias Green, an oceanographer at Bangor University in the United Kingdom, told Live Science. Meanwhile, Australia is drifting north on a collision course with Korea and Japan, and Africa is rotating northward toward Europe. These movements, of course, are happening at the rate of centimeters per year, about the speed that your hair and nails grow.
Mitchell and Green said there are a handful of prevailing ideas about what the next geologic game of "Tetris" might look like. The Atlantic Ocean could close up, with northern Canada crashing into the Iberian Peninsula and South America colliding with southern Africa roughly where Pangea used to be. Or the Pacific Ocean could disappear, subsumed by Asia and North America. Mitchell had one additional, out-of-the-box hypothesis: that North America and Asia might move northward to converge over the Arctic, quashing the Arctic Ocean.
So, how might the formation of the next Pangea affect life on Earth (assuming there's still flora and fauna 300 million years from now)?
It will definitely change existing weather and climate patterns and affect existing biodiversity, Green said. "The largest mass extinction event to date happened during Pangea," Green said. "Was that because we were on a supercontinent? Or coincidence?"
He's referring to the Permian-Triassic extinction, dubbed "the Great Dying," when 90 percent of the world's species died out 250 million years ago. Just after Pangea formed, two major volcanic eruptions spewed large amounts of methane and carbon dioxide into the atmosphere, which may have contributed to the mass die-off. But scientists aren’t in agreement about whether plate tectonics and the convection processes that formed Pangea are linked to these critical volcanic events.
It's unclear what's in store for life on Earth when the next supercontinent forms. But, thanks to scientists like Mitchell and Green, we may at least know what our atlases should look like a few hundred million years from now.
Original article on Live Science.