Mad about Science: Pangaea

By Brenden Bobby
Reader Columnist

A lot can happen in a billion years. The continents, as we know them, have not always been laid out in the way they appear on our maps. A keen eye might notice that certain coastlines could almost perfectly fit together like a jigsaw puzzle. Beginning about 335 million years ago, this was exactly the case, as all of the continents were slammed together into a colossal supercontinent called Pangaea.

You may be wondering how we could possibly conceive of Pangaea — it was so long ago and spanned several documented extinction events. Luckily, something as large as a continent leaves lots of evidence behind whenever it moves.

The first and most obvious clue lies with the coastlines of South America and Africa. These two continents can fit together almost perfectly. More than simply appearing close together, archaeologists have discovered fossils of identical terrestrial species that existed near the coasts of both continents from the same point in time, based on the layer of rock from which they were extracted. This shows that these two continents were close enough together at a certain time for a relatively slow creature to walk from one to the other without worrying about a pesky ocean in the way.

Another hidden clue is the formation of mountains. Some mountain ranges were formed at the same time, despite being currently separated by an ocean several times over. One instance of this is the Appalachian Mountains, which were formed at the same time as the Caledonides, which have been fragmented between Scotland, Greenland and Scandinavia. These had been formed as a chain, but were pulled apart as the continents drifted from each other.

The formation of Pangaea took an incredibly long time. It truly began during the late Cambrian period, around 490 million years ago. Over the 180 million years to follow, the continent that would become North America and parts of Siberia collided with basically everything else — a massive continent called Gondwana — and created a huge north-south supercontinent on one side of the Earth. Most continents now are fairly evenly distributed around the globe, but Pangaea was essentially a huge strip of land that stretched from the North to the South poles. Most of terrestrial Earth would have been experiencing daylight at roughly the same time, with the exception of the farthest eastern regions of what would eventually become Australia and Eurasia, respectively.

Trying to figure out what kind of climates may have been on Earth over a period of 160 million years is difficult. It’s absolutely certain that the presence of a supercontinent created some really wild weather patterns and fossil evidence shows that extremes were the norm for a very long time.

Earth’s giant ocean meant two things. One was that wind had a whole lot of open space to move around without obstruction, and that the day and night cycle meant the superocean would spend a lot of time heating up and evaporating, and a lot of time cooling and condensing. This meant the rain cycle was likely erratic and extreme and created huge mega-monsoons that would slam into the coastal regions of Pangaea and saturate everything for months. However, this was likely restricted to the coasts due to the sheer size of the continent, and the central portions of Pangaea were likely extremely dry and arid.

A mixture of mass extinctions and extreme climates meant that biodiversity plummeted during large portions of Pangaea’s existence, particularly toward the beginning of its formation. This is supported by a reduction of coal in rock layers of this time, indicating that plant life became more rare, likely because of the aridity of the colossal landmass. The poles may have experienced less extreme weather and fewer ice ages, and may have been able to support something akin to the Siberian Taiga, but actual rainforests were likely a rarity until the late Jurassic or even Cretaceous Period once the continent began to break apart.

Pangaea wasn’t the first supercontinent to exist on Earth. We know of at least four preceding it: Gondwana, Pannotia, Rodinia and Columbia (Nuna). It’s possible that there may have been at least five preceding those as well, but those are largely hypothetical.

It’s possible that Pangaea wasn’t the last supercontinent on Earth. Just like your least favorite Marvel movie adaptation, Pangaea may rise again as the continents drift together. Pangaea Proxima is the name of this hypothetical supercontinent. It’s hypothesized that North and South America will drift into one another and pull into Africa and Eurasia to create a huge landmass spanning east to west. Climates would likely be reflective of the original Pangaea with a plethora of heat, desertification and humid coastlines. 

Whether or not human beings will be here to see that happen in the next 250 million years is largely up to speculation — hopefully we’ll all have made friends with each other and figured out how not to go extinct by that time. I couldn’t think of anything more embarrassing for our species than alien archaeologists extracting a fossilized skeleton of a human taking a selfie.

Stay curious, 7B.