Pangaea might have contributed to one of the world's worst mass extinctions
You are probably more than familiar with the map of the world today. The position and extent of the continents may even have been a fundamental driving force for the development of our species, cultures, and history. Author Jared Diamond argued this in his controversial 1997 work Guns, Germs, and Steel.
But, in the grander scheme of the universe and of Earth's long history, the current arrangement of the continents is but a snapshot in time of an ever-evolving and ever-changing surface. Through the power of a process known as plate tectonics, the crust of the Earth is constantly in flux, with the continents wandering around it over time.
At certain times in Earth's history, this has led to all of the world's continents coalescing in a giant car crash millions of years in the making. These giant continental pileups are called supercontinents, and they are something of an occupational hazard for the landmasses of the globe.
In fact, some researchers argue that there is a 'supercontinent cycle', where, over the course of hundreds of millions of years the tectonic plates drift apart and then back together again to form supercontinents.
Let's take a closer look at the latest, and most famous, of these supercontinents - the mighty Pangaea.
What was Pangaea?
Pangaea, also spelled Pangea, was a massive supercontinent that incorporated almost all the landmasses on Earth in one place. Roughly resembling a large "Pacman" or letter "C", the supercontinent would have stretched from each pole of the Earth in one continuous landmass.
Its name is derived from the Greek pangaia, meaning, roughly, “all the Earth.”
This landmass would last for around 150 million years before beginning to spectacularly break apart about 200 million years ago during the Early Jurassic Epoch (about 201 million to 174 million years ago). Throughout the Mesozoic (Triassic to Cretaceous eras), Pangaea split into two major continents called Laurasia (in the North) and Gondwanaland (in the South) with the embryonic Atlantic Ocean separating them.
These continents would further subdivide over time to eventually form the map of the world we all know so well today.
Pangea’s existence was first proposed in 1912 by German meteorologist Alfred Wegener as a part of his theory of continental drift, a now widely accepted geological process.
What evidence do we have that Pangaea actually existed?
As the astronaut Neil Armstrong once said, "geologists have a saying - rock remembers". The main evidence we have for any past events, especially millions of years ago, is from studying rock formations and their contents.
Fossils, chemical analyses, mineral content, etc, all tell us a tale of what was happening when a piece of rock was originally formed. By careful analysis of rock formations locally and around the world, geologists are able to paint a picture of past conditions on the Earth.
Part of this process in the field of paleogeography, or the study of ancient geography, tries to piece together the physical features of the Earth in the distant past, including landmasses like supercontinents.
Much like a giant jigsaw puzzle, it is possible to find rock formations that have the exact same composition but are located in different parts of the world. So, for example, there are some types of igneous rock in Scotland that cannot be found anywhere else except in some parts of Greenland and the United States.
This indicates to geologists that Scotland (and not the rest of the UK), must have once been connected to these parts of Greenland and the United States in the past. In fact, it is now believed that 500 million years ago Scotland was separated from England and Wales by the ancient Lapetus Ocean. In fact, it is thought that the Scottish Highlands, the Appalachians, the Ouachita Mountains, and the Little Atlas of Morocco were once part of the same mountain range, the Central Pangean Mountains.
Scotland eventually separated from Greenland and Noth America about 60 million years ago when the North Atlantic began to form.
Many other examples exist, including the rocks that made up a series of enormous Gondwana mountains, which can now be found in both Brazil and northern Africa and date to the same period.
These are but two bits of evidence to show that the modern setup of continents is not the way it has always been. By mapping out similar formations like this, geologists can begin to build up a picture of what the world must have looked like.
There are other methods too that help corroborate this kind of reconstruction. Scientists can use the radioactive decay rate of different elements to get fairly precise estimates of the date of rocks hundreds of millions of years old.
Another key piece of evidence, though admittedly directly related to the above, is the study of fossils.
This is a powerful tool in geology and has been a vital tool for piecing together the ancient supercontinents.
Since we can be fairly sure that members of the same species probably lived fairly close together (at least to begin with) they can indicate that the places they are found were probably geographically close at one point.
Today, we can find various fossils of the same species on completely different continents. For example, fossils of the same species (Lystrosaurus) of small, land-based reptiles have been found in Antarctica, India, and South Africa. As these creatures were land-dwellers, we can be fairly certain that they would not have been able to travel across vast distances of water like the Atlantic Ocean.
This would indicate that when these creatures existed, those parts of Antarctica, India, and South Africa, must have been connected in some way in the past! There are many other, similar, examples in the fossil record.
But, if that still isn't enough corroborating evidence for you, geologists can also employ the power of physics. A specialist field called paleomagnetism has also been employed to add further weight to our confidence in the Pangaea hypothesis.
Some rocks, usually igneous (made from lava or magma) contain magnetic-sensitive minerals like those that are iron-titanium oxide rich, which can be studied to discover their relative position on Earth when they formed. Since these minerals will align within the Earth's magnetic field when the rock forms, they offer another interesting type of supporting evidence for Pangaea.
By looking at the orientation of these grains in the rock, and comparing them to the known location of Earth’s magnetic pole at the time when they were formed, scientists can get an idea of where the rocks were formed. You can liken this to looking at tiny compasses that have been locked in position.
When geologists study ancient rocks, like basalt, they can effectively rotate the land area around to see what orientation they would have been in the past. If this is done en masse and compared to other rocks of similar age, we get another powerful piece of evidence for reconstructing the ancient supercontinent.
5 prodigious Pangaea facts
Looking for some more information on Pangaea? Then you've come to the right place.
Read on to find some more fascinating facts about Pangaea and the potential future of the planet's continents.
1. Pangaea may be reborn in the future
As we've already discussed, at the end of the Permian Period, all the major landmasses of the world were joined together into what geologists call Pangaea. During the Triassic Period (about 200 million years ago) this supercontinent began to break apart.
We'll discuss some of the current theories about why this happened in a moment, but the process (if watched from space in fast forward) would resemble a slow-motion explosion. The process starts slowly at first, with the formation of Laurasia and Gondwanaland as continents drifted apart, but things appear to rapidly accelerate from the Jurassic Period (1bout 150 million years ago) onwards.
By the end of the Cretaceous (about 65 million years ago), the basic building blocks of our modern continents are, more or less, recognizable and resemble massive shards of the shattered former supercontinent. Obviously, the "explosion" is happening on a single spherical plane, so the pieces are very limited in where they can travel in "space".
The chunks of the former Pangaea continue to spread across the surface of the Earth into the modern-day with India impacting the "underside" of Asia, the African chunk hitting Southern Europe, and the Americas conjoining. Incredibly, this process is nowhere near finished, and plate tectonics will change the features of our planet's surface well into the future.
It is notoriously difficult to predict what the future shape of Earth's landmasses may look like, but it appears another supercontinent is on the cards. Notionally called Pangaea Proxima, it is believed this new supercontinent will form roughly 200 million years in the future.
2. Pangaea would have been a land of extremes
Pangaea was so massive, that the climate would have varied enormously across it. The interior of the continent, for example, would likely have received very little rain and was probably incredibly arid and hot.
It is also important to note, that average temperatures at the time of Pangaewere incredibly high compared to those today. Scientists believe that temperatures were about 38 degrees Fahrenheit (20 degrees Celsius) hotter in the summer, and atmospheric carbon dioxide was five to 20 times greater than today.
Some modern studies using climate models have also shown that the interior of Pangaea was also probably very seasonal. A 2016 study, for example, used geological data from the Moradi Formation in Northern Niger.
The rocks here consist of layered fossilized soils (called, funnily enough, paleosols), to reconstruct the ecosystem and climate during the time period when Pangaea existed. They found that this region would have resembled the modern-day Namib Desert in Africa or Lake Eyre Basin in Australia.
Today, the climate in these regions is generally arid with short, recurring wet periods that occasionally included catastrophic flash floods.
As we know today, from the locations of fossil fuels initially formed in this period, other parts of the supercontinent would have been incredibly lush, dense, jungle-like areas. Those parts of Pangaea that now form the coal-rich areas of the United States and Europe were probably located on or near the equator and would have resembled the modern-day Amazon (except with very different plants and creatures).
The coastal regions wouldn't be too dissimilar to today with the exception of course, of now long-extinct fauna and flora.
3. Pangaea might have contributed to one of the world's worst mass extinctions
At the end of the Permian Period (circa 250 million years ago), one of the worst, if not the worst, mass extinction events devastated life on Earth. Estimates vary, but somewhere in the region of 70%-90% of all life was wiped off the face of the Earth.
The loss of life was so immense, that the event is generally known as "the Great Dying" and it formed the boundary between the Permian and Triassic periods.
Prior to the extinction event, the predominant form of life on land and in the sea were large reptiles and synapsids (mammal-like reptiles and our ancestors).
Geologists and paleontologists can't be entirely sure why this happened. Recent papers suggest volcanic activity led to the release of an immense amount of greenhouse gases, leading to global warming and ocean acidification on a vast scale.
However it occurred, the event changed life on our planet forever. It also helped paved the way for the rise of the dinosaurs and their descendants. The massed volcanism would have also driven the breakup of Pangaea.
We know this because in the area we now call Siberia, enormous flood basalts have been found from that time. These effusions released huge amounts of CO2 and other gasses into the atmosphere.
Other theories include a large asteroid impact or a nearby supernova exposure. Or, it could have been a combination of several factors.
Such was the change to the global climate that nowhere on Earth appears to have been a safe haven. Many lineages were destroyed never to return including the mighty sea scorpions, trilobites, and many more.
4. Pangaea is the most recent supercontinent we know about
As far as we know, Pangaea is the most recent supercontinent that geologists have been able to piece together. There are thought to have been many others before Pangaea, but geologists are less confident about their reconstructions of these.
This is based, in part, on a very rough rule of thumb of supercontinent formation and breakup over cycles of around 400-500 million years.
Pangaea itself took hundreds of millions of years to come together, and was, itself, the amalgamation of other larger continents. The process of building the massive rock Pacman started around 480 million years ago when a large continent called Laurentia (which includes present-day North America) merged with several other micro-continents to form Euramerica.
We are confident you can work out what part of the modern world that includes.
Euramerica, in turn, then eventually collided with Gondwana, another supercontinent that included Africa, Australia, South America, and the Indian subcontinent. Pangaea lasted for around a hundred million years, before completely breaking up in the Jurassic.
5. You can still see the pieces of the Pangaea puzzle today
We have already discussed some of the tools used to piece together what Pangaea probably looked like above, but there is another, very convincing and easy-to-understand method too. This is the fact that modern continents and their continental shelves, actually fit together like a giant jigsaw (sort of).
If we could drain all the oceans, you would see that all the continents on the planet actually stretch out a bit under the sea. As these parts are normally flooded, we never really see them.
Most continental shelves are very broad and tend to be gently sloping plains covered by relatively shallow water. Water depth over the continental shelves can vary widely but tend to average about 60 meters (200 feet).
By using a range of techniques like sonar, scientists have been able to map these areas in very high resolution over the years. By studying and comparing these areas, it is actually possible to reconstruct their past with high amounts of certainty.
For example, the west coast of Africa and the East coast of the Americas appear to be a pretty good fit. If you compress Mexico (nothing personal) and stack North and South America on top of one another, Morocco to about Gabon will fit snuggly against the west and south coast of the United States.
The east coast of South America and the west coast of Africa will also fit together very nicely. As we know today, this is no coincidence, and the formation of the Atlantic Ocean was the result of these three continents going their separate ways.
This separation occurred, very roughly, 140 million years ago, but it indicates that these three continents were connected at some point in the past.
The very same process of mapping the seafloor in high definition has also revealed some other incredibly important supporting evidence for plate tectonics and, by extension, the ancient supercontinent. Called the mid-ocean ridges, these are enormous "wounds" or "scars" that run, very approximately, along the mid-point between modern continents on the sea floor (with the exception of places like Iceland).
These structures, it has since been discovered, are where oceanic crust is formed as magma spews from the mantle into the deep sea. Much like an open wound on your skin, the liquid hot rock rises from the mantle, cools, and forms new slabs of rock at the surface.
What's more, these ridge systems create crust at differing rates, with those in the Pacific generally more rapid than others like the mid-Atlantic ridge.
Since you can't continuously create new crust without causing the overall size of the crust to expand over time, somewhere along the line rock needs to be returned to the mantle and destroyed.
Oceanic crust is heavier and denser than continental crust and accumulates material from dead ocean organisms and sediment dumping as it nears continental shelves. This adds extra weight to the oceanic crust, causing it to eventually sink below the less dense continental crust.
This is the core idea behind plate tectonics, and the process of creation and destruction creates a kind of conveyor belt that pushes continents around. The ridges themselves actually form shapes suspiciously similar to the continental jigsaw pieces we discussed earlier.
It is highly unlikely this is just a coincidence.
And that ancient supercontinent boffins is your lot for today.
While the mechanics of its formation are still largely theoretical, the idea behind such a large continent as Pangaea is not pure fantasy. The gradual accumulation of corroborating evidence over time has lest most geologists to believe that the world we see today is not as it has always been.
Several core principles in geology, like plate tectonics, can actually be observed in action today, so rewinding the movie of Earth's continental evolution is largely a very safe bet - scientifically speaking.
Professor Gretchen Benedix is an astrogeologist and cosmic mineralogist who studies meteorites and figures the forming stages of the solar system.