The giant supercontinent “Pangaea”
About 200 million years ago, all the continents were together as one giant supercontinent known as Pangaea.
Over time, these continents have broken apart. We know they were together because it’s not only that continents fit together like a puzzle…
But we’ve found the same types of rocks on the west coast of Africa and the east coast of South America. This means they must’ve formed when the continents were together.
We’ve also found the same types of plants and animal fossils at both coasts. We know that plants couldn’t float across ocean and animals couldn’t have swim.
But people didn’t always believe Pangaea
Back in the 1700s, people believed that the size and shape of the continents were the same for millions of years.
In other words:
If you looked at a map now and compared it to a map millions of years ago, they would be exactly the same.
In the 1400s, cartographers created maps similar to the ones we see today.
But there was something that stood out in these maps:
Could all these pieces fit together somehow? For example, the Atlantic coast of Africa and South America connected particularly well.
Eduardo Suess’ supercontinent theory of “Gondwana” in 1861
The general consensus from scientists in the late 1800s was that the continents have remained like they have for millions of years. No one believed the continents all tore apart from each other.
Except when an Austrian geologist by the name of Eduard Suess theorized the idea of the supercontinents in 1861.
He proposed the world was all connected as one giant continent “Gondwana” at one time. He also theorized that there was one giant ocean – “Tethys Ocean”
But the scientific community still questioned the idea of a supercontinents. Indeed, the world fit reasonably well but it didn’t fit perfectly…
Alfred Wegner’s supercontinent theory “Pangaea” in 1912
German geographer Alfred Wegener introduced the idea of piecing the world at continental shelves. Instead of at the landmasses you see from above, the water levels off at the continental shelf. Now, if you cut each continent and islands at the continental shelf, they match even better. And he was right, as the correlation did improve.
In 1912, Alfred Wegener thought that all continents were connected as one giant landmass called “Pangaea” (sometimes spelled “Pangea”). He also introduced the idea that 200 million years ago, Pangaea tore apart. It was through plate tectonics that drove continental drift and the moving of continents.
Finally, we had an answer for where the energy could come from to pull continents apart. It was plate tectonics and continental drift which had enough tensional force to split continents apart.
Again, the idea was disliked amongst scientists and really not accepted. But even today, Alfred Wegener’s theory of plate tectonics and the supercontinent Pangaea is the most established and recognized.
The importance of plate tectonics splitting Pangaea apart
The Earth’s crust has 15 or 20 separate pieces. The reason why they look like they do is because they broke apart. The Atlantic Ocean actually formed when the continents of Africa and South America moved away from each other.
These pieces (plate tectonics) ride on soft melted rock called the asthenosphere underneath. If you’re making new ocean bottom in one place, somewhere it’s getting rid of it. Because the Earth is staying the same size. So where does old oceanic crust get consumed into the mantle again?
At deep sea trenches, this is where oceanic crust goes beneath. For the volume that you make at an oceanic ridge, the volume dissolves at deep sea trenches.
The start of this process is at deep sea trenches. They break and dive down into the mantle getting re-consumed at zones of subduction.
Since the formation of Pangea, continental land mass has gone through addition and subtraction. New land is being formed and destroyed every day as part of the rock cycle. As the Earth is billions of years old, it has undergone significant change due to plate tectonics.