Will there ever by another Pangaea?
What will the world look like in 300 million years? (Image credit: Shutterstock)
Just before the dawn of the dinosaurs — roughly 251 million years ago — Earth's
continents abutted one another, merging to form the supercontinent Pangaea. 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 Pangaea?
The answer is yes. Pangaea wasn't the first supercontinent to form during Earth's 4.5billion-year geologic history, and it won't be the last.
"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
Pangaea' 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.
This diagram shows the Georgetown terrane, in green, joining Australia around 1.6 billion years ago
during the formation of the supercontinent Nuna. (Image credit: Geology)
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.
Pangaea, seen here during the Permian, kind of looks like an ancient Pac-Man. (Image credit:
Shutterstock)
Scientists can track tectonic plate movements using GPS instruments (optional to click
on link for more info). 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 Pangaea, dubbed
Amasia (or Pangaea 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 Pangaea 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 Pangaea of the future (click link or image to see
animation) 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 our 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 Pangaea used to be. Or the Pacific Ocean could
disappear, subsumed by Asia and North America. Mitchell had one additional, out-ofthe-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 Pangaea 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
Pangaea," Green said. "Was that because we were on a supercontinent? Or
coincidence?”
He's referring to the Permian-Triassic extinction, dubbed "the Great Dying," (optional to
click link) when 90% of the world's species died out 250 million years ago. Just after
Pangaea 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 Pangaea 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.
Attribution: Will there ever be another Pangaea? By LiveScience. Used for educational
purposes only.