by The earth today consists of six or seven continents and four or five oceans, depending on who you ask. But this was not always the case. Over geologic time, continents “drift” on tectonic plates – large chunks of Earth’s crust that float on a hot plastic layer of the mantle and periodically bump into each other and break apart. Very often (that is, every several hundred million years or so), conditions are such that most or all of the continents clump together to form one larger landmass called a supercontinent. Notable supercontinents of the past include Laurasia, Gondwana (or Gondwanaland), and — the mother of all supercontinents — Pangaea, which lasted from the Early Permian (about 299 million years ago) to the Early Jurassic (about 200 million years ago). .
But how do we know that Pangea really existed? After all, humans only evolved a few hundred thousand years ago, so no one was there to witness this geomorphological savagery. How did scientists “discover” Pangea and other supercontinents in the past? Nowadays, they can study the geological record and use radiometric dating, seismic surveys, and other technologies to build maps of how the world has looked at different points in Earth’s history. The existence of Pangea was first proposed in 1912, long before these instruments were invented and the modern theory of plate tectonics was developed.
German meteorologist Alfred Wegener first introduced the concept of Pangea (meaning “all lands”) along with the first comprehensive theory of continental drift, the idea that the Earth’s continents move slowly relative to one another, at a conference in 1912 and later in his book. Origin of continents and oceans (1915). Like a handful of other scholars before him, such as the nineteenth-century German naturalist Alexander von Humboldt, Wegener became impressed by the similarity between the coasts of eastern South America and western Africa and wondered if those lands had ever been joined together. Sometime around 1910, he began to consider whether all of the present-day Earth’s continents had once formed one great mass, or supercontinent, long ago, and then separated. Wegener’s view was at odds with the prevailing paradigm at the time, which suggested that large parts of the continents floundered and sank under oceans over time.
Wegener noted that the plan, geomorphology (rocks and topography), and climatic belts of eastern South America were similar to those of the southwestern coast of Africa. He also argued that fossils of certain plants and animals appeared on both continents, and that while these organisms were alive, they could not have crossed the breadth of the South Atlantic Ocean that now separates the two continents. So, logic would suggest that South America and Africa were once part of the same landmass. Wegener concluded that South America and Africa (as well as other countries) were connected to each other, possibly by land bridges, about 250 million years ago. He also believed that Pangea persisted throughout most of Earth’s history. Wegener relied on the work of Austrian geologist Eduard Suess, who (although he was a staunch proponent of sunken continents) was the first to develop the concept of Gondwanaland—a supercontinent that existed from 600 million to 180 million years ago and is composed of present-day continents. Day of Africa, South America, Australia, India and Antarctica. Soss spotted rock formations in India that matched well in age and composition with similar formations across the southern hemisphere. Wegener used Suess’s work to support his hypothesis of continental drift and considered Gondwanaland to be the southern half of Pangea.
Despite the existence of this geological and paleontological evidence, Wegener’s theory of continental drift was not accepted by the scientific community, because his explanation of the driving forces behind continental motion (which he said stemmed from the gravitational force that created the Earth’s equatorial bulge or the gravitational pull of the Moon) ) has been refuted. Wegener died in 1930, long before many of his ideas regarding Pangea and continental drift were proven. However, other scientists, such as South African geologist Alexandre du Toit, continued to collect evidence supporting continental drift. Du Toit proposed the idea of Laurasia – an ancient supercontinent in the northern hemisphere comprising North America, Europe and Asia (excluding peninsular India) – in his book Our wandering continents (1937).
Advances in rock and mineral dating, sonar, and geophysics eventually proved Wegener. It was later shown that the rock formations in eastern North America, western Europe, and northwest Africa had a common origin, and that they overlapped over time with the existence of Gondwanaland. Together, these discoveries supported the existence of Pangea. Additionally, evidence supporting continental drift emerged during the 20th century, and scientists described a mechanism that appeared to explain continental motion by the 1960s, which was incorporated into the modern theory of plate tectonics. This mechanism was a process of mantle convection, in which hot mantle rises from the Earth’s interior to the surface to push tectonic plates in opposite directions. Although so-called spreading centers (linear boundaries between diverging plates on the ocean floor characterized by rising magma) have been shown to exist, an explanation of how mantle convection works remains elusive to this day.
Modern geology has shown that Pangea did indeed exist. However, in contrast to Wegener’s thinking, geologists note that other Pangea-like supercontinents likely predated Pangea, including Rodinia (about 1 billion years ago) and Panotia (about 600 million years ago). Today, the Earth’s tectonic plates continue to move, and their movement is slowly bringing the continents back together. Within the next 250 million years, Africa and the Americas will merge with Eurasia to form a supercontinent approaching Pangean proportions. Such an episodic grouping of the world’s landmasses is called the supercontinent cycle, or the Wegener cycle in Wegener’s honour.
