We all know that the Earth has seven continents – Asia, Europe, Africa, Antarctica, Australia, North America and South America. This is what the Earth looks like today, but it was not always the case. Millions of years before humanity existed, millions of years before the dinosaurs existed even, the Earth had a much different look. Instead of seven distinct continents, there was one large landmass – a supercontinent, so to speak – which was called Pangaea. “Supercontinent” is a term used for a large landmass formed by the convergence of multiple continents. This supercontinent incorporated almost all the landmasses on Earth and was surrounded by the Panthalassa, a single large ocean. The supercontinent of Pangaea subsequently underwent fragmentation, the pieces forming the Earth’s current continents.
THE IDEA BEHIND THE NAME AND ITS CONCEPT
The name “Pangaea” is derived from the Ancient Greek words “pan” and “Gaia”. The word “pan” means all, entire or whole and the “Gaia” was the Ancient Greek goddess of the Earth, a personification of Earth itself. Alfred Wegener, the originator of the scientific theory of continental drift, first suggested the idea of the existence of a singular landmass or a supercontinent in his 1912 publication The Origin of Continents (Die Entstehung der Kontinente). He expanded upon his hypothesis in his 1915 book The Origin of Continents and Oceans (Die Entstehung der Kontinente und Ozeane), in which he postulated that, before breaking up and drifting to their present locations, all the continents had formed a single supercontinent that he called the “Urkontinent”.
EVIDENCE OF THIS SUPERCONTINENT
Coal deposits found in Pennsylvania, USA have a similar composition to several deposits spanning across Poland, Great Britain and Germany from the same time period. This is tangible evidence that North America and Europe must have once been a single contiguous landmass. The orientation of magnetic minerals in geologic sediments reveals how Earth’s magnetic poles migrated over time. Geologists can use this orientation to track tectonic plate movements.
In recovered fossils, records indicate that identical plants, such as the extinct seed fern Glossopteris, are found on widely disparate continents. Fossils of the therapsid Lystrosaurus have been found in South Africa, India and Antarctica. The freshwater reptile Mesosaurus has been found in local regions of the coasts of Brazil and West Africa, which are quite far apart in the present day. Mountain chains that now lie on different continents, such as the Appalachians in the United States and the Atlas Mountains in Morocco, were all part of the Central Pangaea Mountains, offering further evidence that points to the existence of a pre-historic super landmass.
Glacial deposits of the same age and structure have been discovered on many separate continents that would have been together in the continent of Pangaea.
HOW DID PANGAEA FORM?
Pangaea formed through a gradual process spanning a few hundred million years. Beginning about 480 million years ago, a continent called Laurentia, which includes parts of North America, merged with several other micro-continents to form Euramerica. Euramerica eventually collided with Gondwana, another supercontinent that included Africa, Australia, South America and the Indian subcontinent.
Throughout the course of Earth’s history, the formation of supercontinents has occurred in a cyclic manner. There may have been several others before Pangaea. The fourth-last supercontinent, called Columbia or Nuna, appears to have assembled in the period 2.0–1.8 billion years ago.
The supercontinent Rodinia was formed when Nuna broke up. Rodinia lasted from about 1.1 billion years ago until about 750 million years ago. When Rodinia broke up, three new supercontinents emerged from the split: Proto-Laurasia, Proto-Gondwana, and the Congo craton. Proto-Laurasia and Proto-Gondwana were separated by the Proto-Tethys Ocean. It was Proto-Laurasia’s turn to split after this, forming Laurentia, Siberia, and Baltica. The splitting also created two new oceans, the Iapetus Ocean and Paleoasian Ocean. A large portion of these masses coalesced to form a relatively short-lived landmass, Pannotia, which then broke up, giving rise to the continents of Laurentia, Baltica, and the southern supercontinent of Gondwana. In the Earliest Ordovician period, the microcontinent of Avalonia broke free from the supercontinent of Gondwana and began drifting towards Laurentia. Baltica, Laurentia, and Avalonia all coalesced by the end of the Ordovician era to form a minor supercontinent called Euramerica or Laurussia. During this whole process, Gondwana itself was drifting away, heading towards the North Pole. This was the first step in the formation of Pangaea. The second step in the formation of Pangaea was the collision of Gondwana with Euramerica. Siberia had been existing as a separate continent for millions of years since the break up of the supercontinent Pannotia. The Kazakhstania microcontinent collided with Siberia and Western Kazakhstania collided with Baltica in the Late Carboniferous, causing the formation of the Ural Mountains as well as the supercontinent of Laurasia. This was the last step of the formation of Pangaea. By the late Silurian, North and South China split from Gondwana and started to head northward, finally leading to the collision of North China with Siberia, completing closing the Proto-Tethys Ocean.
LIFE AND CLIMATE ON PANGAEA
Being one massive landmass, Pangaea would have weather cycles and climate patterns quite different from what we’re used to in the present day. The interior of the continent may have been utterly dry, as it was locked behind massive mountain chains that blocked all moisture or rainfall. However, coal deposits that have been discovered in the United States and Europe reveal that the regions of Pangaea close to the equator must have had lush tropical climates, since such conditions are required for the formation of coal. Climate models confirm that the continental interior of Pangaea was extremely seasonal, according to a 2016 article in the journal Palaeogeography, Palaeoclimatology, Palaeoecology. Similar to the modern-day African Namib Desert and the Lake Eyre Basin in Australia, the climate was generally dry with short, cyclic periods of precipitation that occasionally included devastating flash floods. The formation of each environment and climate on Pangaea is due to plate tectonics As a result of these shifts and changes, different climatic conditions developed on Pangaea. Although the involvement of plate tectonic movements was essential in the formation of later land masses, it was also essential in the placement, climate, environments, habitats, and overall structure of Pangaea.
Not much is currently known about life on this supercontinent due to the lack of fossilized remains, which serve as sources of acceptable evidence for the existence of organic life. Pangaea existed for almost a 160 million years, and during that time period several animals flourished, including the Traversodontidae, a family of plant-eating animals that includes the ancestors of mammals. A variety of insect species (including beetles and cicadas) also thrived, during the Permian period 299 to 252 million years ago. The Permian period was a geologic period which spanned 47 million years from the end of the Carboniferous period 298.9 million years ago to the beginning of the Triassic period 251.902 million years ago. A few marine animals have alsobeen identified – the Ammonites and Brachiopods. Additionally, evidence pointing towards large reefs with varying ecosystems has also been uncovered. About 230 million years ago some of the earliest dinosaurs emerged on Pangaea, including theropods, largely carnivorous dinosaurs that mostly had air-filled bones and feathers similar to birds.
THE FRAGMENTATION OF PANGAEA AND THE WORLD AS WE KNOW IT TODAY
Scientists have created mathematical, 3D simulation models to correctly interpret the mechanisms behind continental movement. The models show how tectonic plate motion and mantle convection forces worked in tandem to fragment and move large landmasses. Pangaea’s large mass insulated the mantle underneath, causing mantle flows that triggered the initial breakup of the supercontinent. Radioactive decay of the upper mantle raised the temperature, causing upward mantle flows that broke off the Indian subcontinent and initiated its northern movement.
The reconfiguration of continents and oceans after the disintegration of Pangaea changed the world’s climatic conditions and weather cycles. There is scientific evidence that points to the fact that this change was drastic. When the continents separated and reformed themselves, it altered the flow of the oceanic currents and winds. The reorganization of the continents changed the structures of the oceans and seaways. The restructuring of the continents, changed and altered the distribution of warmth and coolness of the oceans. When North and South America connected, it stopped the equatorial currents that flowed from the Atlantic Ocean to the Pacific Ocean. Researchers have found evidence by using computer hydrological models to show that this strengthened the Gulf Stream by diverting more warm currents towards Europe. Warm waters at higher latitudes led to higher rates of evaporation and eventually the accumulation of more atmospheric moisture. The separation of Australia and Antarctica led to the formation of the Antarctic Ocean. Ocean currents in this newly formed ocean created a circumpolar current. The creation of the new ocean that caused a circumpolar current eventually led to atmospheric currents that rotated from west to east. Atmospheric and oceanic currents stopped the transfer of warm, tropical air and water to the higher latitudes. As a result of the warm air and currents moving northward, Antarctica cooled down so much that it became frigid.
The scientific reasoning behind all of the changes is the thoery of Continental Drift. This theory was first suggested by Alfred Wegener, who explained how the continents shifted on the Earth’s surface and how that affected a variety of different aspects such as climate, rock formations found on different continents and fossils belonging to different flora and fauna. Wegener studied plant fossils from the Arctic of Svalbard, Norway. He determined that such plants were not adapted to a frigid climate. The fossils he found were from tropical plants that were adapted to thrive in tropical climates. Wegener assumed that plant fossils were incapable of travelling to a different place, so he suspected that Svalbard had had a warmer, less frigid climate in the past. Although many of Alfred Wegener’s theories and conclusions were valid, scientists are constantly coming up with new innovative ideas or reasoning behind why certain things happen. Wegener’s theory of Continental Drift was later replaced by the theory of tectonic plates.
THE FINAL STRUCTURE OF THE EARTH
Scientists Masaki Yoshida and M. Santhosh have created geological models to predict mantle convection and continental movement patterns 250 million years in the future. These models suggest that over millions of years, the Pacific Ocean will close as Australia, North America, Africa, and Eurasia come together in the Northern Hemisphere. Eventually, these continents will merge, forming a supercontinent called “Amasia.” The two remaining continents, Antarctica and South America, are predicted to remain relatively immobile and separate from the new supercontinent.
The world that we know today will not stay the same. Throughout the course of history, tectonic plate movements have led to continental drifts and fragmentation of large landmasses. These processes are happening to this day. A 100 million or 200 million years from now, the shape of the world will be very different to what it is right now.
