The mysterious supercontinent Pangea and the appearance of the seven modern continents of Earth

About 320-195 million years ago, Earth didn’t have seven continents. There was a giant “supercontinent” called Pangea (Pangaea), which was surrounded by a single enormous ocean called Panthalassa (Phansalassa).

Sound amazing? Scientists say that the continents have come together and spread apart at least three times before. After all, our planet is 4.5 billion years old. On that time scale, 200 million years ago isn’t such a long time!

What can make the continents move? Plate Tectonics!

The explanation for Pangaea’s formation ushered in the modern theory of plate tectonics, which posits that the Earth’s outer shell is broken up into several plates that slide over Earth’s rocky shell, the mantle.

Over the course of the planet’s 4.5 billion-year history, several supercontinents have formed and broken up, a result of churning and circulation in the Earth’s mantle, which makes up 84% of the planet’s volume, according to the U.S. Geological Survey. This breakup and formation of supercontinents has dramatically altered the planet’s history.

“This is what’s driven the entire evolution of the planet through time. This is the major backbeat of the planet,” said Brendan Murphy, a geology professor at the St. Francis Xavier University, in Antigonish, Nova Scotia.

What evidence do scientists have for Pangea’s existence?

More than a century ago, the scientist Alfred Wegener proposed the notion of an ancient supercontinent, which he named Pangaea (often spelled Pangea), after putting together several lines of evidence. The word “Pangaea” comes from the Greek “pan,” which means “all,” and “gaia” or “Earth,” according to the Etymology Dictionary.

The first and most obvious clue about Pangea’s existence was that the “continents fit together like a tongue and groove,” something that was quite noticeable on any accurate map, Murphy said.

Another telltale hint that Earth’s continents were all one land mass comes from the geologic record.

Coal deposits found in Pennsylvania have a similar composition to those spanning across Poland, Great Britain and Germany from the same time period. That indicates that North America and Europe must have once been a single landmass. And the orientation of magnetic minerals in geologic sediments reveals how Earth’s magnetic poles migrated over geologic time, Murphy said.

In the fossil record, identical plants, such as the extinct seed fern Glossopteris, are found on now widely disparate continents.

And mountain chains that now lie on different continents, such as the Appalachians in the United States and the Atlas Mountains spanning Morocco, Algeria and Tunisia were all part of the Central Pangea Mountains, formed through the collision of the supercontinents Gondwana and Laurussia (Laurasia).

How was Pangea formed?

The supercontinent formed through a gradual process spanning a few hundred million years.

Tectonic plate movement is the reason why Pangea formed, broke up, and why continents still shift positions today. Earth’s outermost layer is composed of several tectonic plates, which glide over the interior layer of earth called the mantle. As these plates move around, they can cause landmasses to inch together, break apart, and transform.

The Pangea timeline spans hundreds of millions of years. In the early Phanerozoic eon (541 million years ago to now), almost all of the continents were in the Southern Hemisphere, with Gondwana, the largest continent, spanning from the South Pole to the equator, according to a chapter in the scientific book “Ancient Supercontinents and the Paleogeography of Earth” (Elsevier, 2021).

The Northern Hemisphere was largely covered by the Panthalassic Ocean.

Another ocean — called Iapetus, after a mythical Greek titan — between the paleo-continents Laurentia, Baltica and Gondwana, began to close during the Ordovician period (485 million to 444 million years ago) and then disappeared during the Silurian period (444 million to 419 million years ago), when Baltica and Avalonia collided with Laurentia to form Laurussia (Laurasia), according to the chapter, “Phanerozoic paleogeography and Pangea.”

Finally, about 320 million years ago, there was a major geological collision, geologically speaking, as Gondwana, Laurussia (Laurasia), and other nearby landmasses smashed together and created Pangea.

However, the supercontinent of Pangea wasn’t quite as big as most people think it was. “Pangea never included all the continents at any one time,” according to the chapter. For instance, during the Carboniferous period (359 million to 299 million years ago) the Paleotethys ocean divided Pangaea from Asian landmasses to the east including Tarim, North China, South China, and Annamia.

Later, during the Permian period (299 million to 251 million years ago), “many former peri-Gondwanan terranes drifted off the north-east Gondwana margin, commencing the opening of the Neotethys Ocean,” according to the chapter.

How and when did Pangea break apart?

Pangaea broke up in several phases between 195 million and 170 million years ago. The breakup began in the early Jurassic period, when the Central Atlantic Ocean opened, according to the chapter. The supercontinent fractured largely along previous sutures.

Gondwana (what is now Africa, South America, Antarctica, India and Australia) first split from Laurasia (Eurasia and North America).

Then about 150 million years ago, Gondwana broke up. India peeled off from Antarctica, and Africa and South America rifted, according to a 1970 article in the Journal of Geophysical Research.

Around 60 million years ago, North America split off from Eurasia.

Protohistory of Pangea

A number of modern geologists believe that the most ancient supercontinent on Earth was Pangea 0. This hypothetical supercontinent could have existed at the end of the Archean (2,500 million years ago).

After disintegrating, Pangea 0 reassembled as Pangea I in the Early Proterozoic (2500-1600 million years ago).

The divergence of Pangea I into separate continents began to occur during the Riphean period (1600-600 million years ago).

Then, the reverse process began — the convergence of the fragments of Pangea I into the new supercontinent Pangea II (600-250 million years ago), the concept of the existence of which was proposed by Alfred Wegener.

Pangea Proxima may appear within the next 250 million years

Today, Earth’s tectonic plates continue to move, and their motions are slowly bringing the continents together once again.

Within the next 250 million years, Africa and the Americas will merge with Eurasia to form a supercontinent that approaches Pangean proportions. Such an episodic assembly of the world’s landmasses has been called the supercontinent cycle.

Other names given to the next supercontinent include Pangea Ultima, Neopangea.

On average, continents move about 5-10 cm per year. This is about the same length our fingernails grow every year. If we could fast-forward into the future, continents will reconnect into another supercontinent. Pangea Proxima or Pangea Ultima is projected as the next supercontinent in 250 million years.

If we incorporate the velocities and trajectories of current plate movement, then we can model how continents will evolve. The landmass itself would extend 13,000 miles with one super-ocean covering two-thirds of Earth.

In the case of Pangea Proxima, it’s an odd-shaped continent because it’s circular with a hole in the middle.

Similar to Pangea, North America would re-collide with the southern part of Africa. South America, Antarctica, and Australia would wrap around to connect with the south of Asia to create a ring of continents. Finally, the hole in the center of Pangea Proxima is a remnant of the Indian Ocean.

The idea of Pangea’s future formation is intriguing, as it would mark a dramatic shift in Earth’s geography, millions of years from now.

By Gilbert Castro | ENC News