Pangaea: The supercontinent that existed on Earth millions of years back
You know that dinosaurs roamed Earth once and that the entire animal species have become smaller over time. But can you imagine any other physical structure of the Earth, different from what it is now?
Millions of years ago, there was no America or Africa or Europe or Asia for that matter. The seven continents that you see today were actually one huge supercontinent known as Pangaea surrounded by one enormous ocean, ‘Panthalassa’. This gigantic continent slowly broke apart and spread out to form the continents and surrounding oceans as we see today.
The giant continent Pangaea
About 320 million years ago, there was a major collision, geologically speaking, when all land merged to form the Pangaea supercontinent. But what led to this collision? Studies suggest that the tectonic plates forming Earth’s outer crust slid over the inner layers until they collided as a landmass surrounded by a massive ocean called Panthalassa.
This supercontinent Pangaea existed for more than 100 million years. Many animal groups thrived during its time. But the existence of Pangaea overlapped with the worst mass extinction in history, the Permian-Triassic extinction event. Also called the Great Dying, it occurred around 252 million years ago and caused 96% of all marine species and around 70% of terrestrial species to go extinct.
How did Pangaea evolve into seven continents?
Between 200 million and 170 million years ago, after the Great Dying event, Pangaea broke up in several phases bit by bit. At first, Pangaea broke into two new continents, Laurasia and Gondwanaland. Laurasia was made of the current-day continents of North America (Greenland), Europe, and Asia. Gondwanaland was made of the present-day continents of Antarctica, Australia and South America.
But how did it break? Pangaea began to be torn apart when a three-pronged fissure grew between Africa, South America, and North America. Rifting began as magma welled up through the weakness in the crust, creating a volcanic rift zone. It broke into several continents in phases over the next millions of years.
How do we know that there was a supercontinent?
You don’t believe this, right? But according to the geologists, the first clue to this mystery is that the "continents fit together like a tongue and groove," something quite noticeable on any accurate map. Another hint that Earth's continents were all one land mass comes from the geologic record.
The rock formations of eastern North America, Western Europe, and northwestern Africa were later found to have a common origin, and they overlapped in time with the presence of Gondwanaland. Together, these discoveries supported the existence of Pangea.
Coal deposits found in Pennsylvania have a similar composition to those spanning Poland, Great Britain and Germany from the same time. 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.
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 Pangaea Mountains once.
Was Pangaea the Earth’s first supercontinent?
Actually, Pangaea wasn’t the first supercontinent of our planet. In fact, throughout the Earth’s 4.5 billion-year history, several supercontinents have formed and broken up, a result of churning and circulation in the Earth's mantle.