We all are accustomed from childhood to the most popular versions of the world map, projections of which are called the Mercator projection and the equal-area projection. Gerardus Mercator in 1569 applied this projection which was later named after him. In modern times, such maps are used not only for the theoretical studies of geography (in schools and universities) but also for various types of navigation (marine navigation, air navigation). But let’s not forget that what we are accustomed to may be different to what people on the other side of the planet are used to.
Projections are intended to help a person understand the real location of the continents and parts of the world. Of course, the closest to the reality is the globe as it follows the shape of the Earth and distortions on the globe are practically minimal. But we will not talk about the type of the representation of the Earth’s surface — the projections, which have their advantages and disadvantages, we will rather discuss the surface itself — the continents.
As was already mentioned in the article about South American flags, people’s worldview from different continents and probably even natural and geographical zones varies widely. This is likely due to the influence of various environmental factors on the person, but the most interesting thing is that even the division of the planet into continents varies depending on the culture and the country. So, five different types of divisions of various detail are usually distinguished, which include different continents such as: America, Afro-Eurasia, Eurasia, Australia, Antarctica, Africa, Europe, Asia, South America and North America.
It is amazing how maps differ among countries. This once again proves us that how heavily thoughts and actions are dependent on the point of view.
The division situation is complicated by the fact that the Earth was not always as it is today. Therefore, I would like to give a brief excursus from the distant past to the present in the context of the formation of the Earth’s surface and talk about the largest continents of our planet of its existence which are called “supercontinents”.
A supercontinent is a large massif of the Earth’s crust which contains almost all of the continental crust of the planet. Thus, a supercontinent is solid, homogenous and indivisible into parts, with the possible exception of some small islands.
During the existence of the Earth seven different supercontinents had been on the surface of the planet which will be presented now.
The first supercontinent is of course the most ancient, which existed about 3.6 to 2.8 billion years ago from the end of the Eoarchean era to the beginning of the Neoarchean era. But its existence is only a theory.
During the existence of the Vaalbara supercontinent there was much less land that today. The size and shape of this formation are uncertain and for the most part are only hypothetical.
The name of the Vaalbara supercontinent origins from the endings of the two most ancient cratons on the planet: Kaapvaal (located mainly in South Africa) and Pilbara (same named region in Western Australia). They are highlighted in red on the modern photo of the Earth.
As we can see, today from one craton to the other there are more than eight thousand kilometers! But it was not always that way.
The next supercontinent, existence of which is also only supposed, formed approximately three billion years ago! It is called Ur from the German prefix “ur” which means “original”, “fountainhead”. Areas of this supercontinent are now parts of Australia, Africa (Madagascar) and India.
Despite the fact that Ur is called a supercontinent its dimensions were significantly less than that of modern Australia. This earthly formation is half a billion years younger than Vaalbara but it is not believed that Ur is not a continuation of Vaalbara nor a successor.
This supercontinent was formed in the Neoarchean era. The name was given in accordance with the Kenoran orogeny. It is believed that Kenorland was only in the law latitudes.
Kenorland formed after the merger of several cratons (including Kaapval and Pilbara). When this supercontinent began to break up, first major glaciations were formed on the Earth.
Columbia existed from 1.8 to 1.5 billons years ago, that is, from the beginning of the Statherian period until the end of the Calymmian.
It is assumed that the supercontinent was about 12,900 kilometers from North to South and about 4800 km in its widest part from West to East.
This supercontinent slowly began to break up into parts from 1.6 to 1.2 billion years ago.
The supercontinent existed in the Proterozoic Eon; it originated about 1.1 billion years ago and broke up about 750 million years ago. The giant land formation was called Rodinia from the Russian “родина” (“rodina” means “motherland”) or “родить” (“rodit” means “to give birth”) and the ocean of that time — Mirovia from the Russian “мир” (“mir” means “world”) or “мировой” (“mirovoi” means “worldwide”, “global”).
The Earth map was already approaching similarity with its’ modern version during the existence of Rodinia.
By the end of the Tonian period the Earth began to turn into a snowball. The theory of “Snowball Earth” refers to this period.
This supercontinent was formed 650 million years ago and lasted until 540 mya. The formation of Pannotia was associated with the break up of Rodinia into Proto-Gondwana and Proto-Laurasia. Since the major part of the land in those days was just near the poles, it is believed that the glaciations reached its peak just about 600 mya.
Also, during the existence of Pannotia there were two proto-oceans — Panthalassa and the Pan-African ocean, which surrounded the supercontinent during the maximum convergence.
At the end of its existence Pannotia broke up into these continents: Gondwana, Baltica, Siberia and Laurentia. These continents will later form the last supercontinent at this moment.
Pangaea existed in the late Paleozoic and early Mesozoic 300 mya. At that time, the supercontinent united all modern continents into one. Many of today’s mountain ranges were formed at the time of collision of continents and lithospheric plates.
The outlines of Pangaea are the most accurate since the existence of the supercontinent is not ancient as that of the previous ones.
At the end of its existence, Pangaea split into Northern and Southern continents — Laurasia and Gondwana. Modern Eurasia and North America formed from Laurasia and Africa, South America, India, Australia and Antarctica formed from Gondwana respectively.
Modern Earth is the result of many complex geological and physical processes. The form that the Earth took in the last periods of its existence has enabled the existence of life on Earth. The answer to the origin of life question should start specifically from this and we should remember that the formation of this very life is an incredibly long process which sprawled for many billions of years. It is hardly possible to imagine so many years, but we can get the closest understanding possible of this process.
Earth is beautiful and in the modern world we have even more opportunities to discover it.