Modern theory of plate tectonics

October 28, 2017

Our Earth came into being when the first debris, whizzing around in the Solar Nebula, barged into each other to form the core of our planet. The heat energy produced as a result of those countless powered collisions was of such extraordinary magnitude that even 4.5 billion years later, the heat has retained its 6000°C Sun-like temperature inside Earth’s core. National Geographic’s documentary on the evolution of Earth through plate tectonics gives a pretty good picture of our planet’s harsh origins.


Today in modern geology, the core is sub-divided into two layers: the inner core and the 5100 kilometers thick outer core. The inner core, although past the melting point of its radioactive and heavy metal constituents, is solid owing to the pressure all of the earth and mantle above exerts on its atoms. In contrast, the outer core is liquid metal, flowing like lava. At the end of the core is the 2900 kilometers mesosphere containing the solid part of the mantle and the 400 kilometers thick asthenosphere making up the semi-solid fluid of the mantle. Directly above the mantle are the lithospheric crusts and the oceanic crusts making up for the surface we know as our home.


The further geological composition of Earth's three main layers: the core, mantle and the crust


In the 1900s, geophysicist Alfred Wegener noticed that the edges of the continents could join up together like the pieces of a puzzle. He theorized the only possible hypothesis, that at some point in time, the continents had all been connected as one big supercontinent. His claim was further supported when engravings of fish species were found in the heights of the Himalayan Mountains. Also fossils of non-native tropical species found in Africa, were discovered in non-tropical regions as well that only proved the theory of continental drift; the continents were moving all the time, 1 to 2 inches every year, and that is why scientists took 200 years to notice and accept the phenomenon. This is the modern theory of plate tectonics, that the topography and landscape of the Earth is always changing and over millions of years adopts whole new looks.

Above: Pangeo Ultima, a predicted future supercontinent. The other possible configuration is Novopangea (New Pangeo) where Antarctica will move northward and Australia will join with East Asia

The earliest known shape of the land was a supercontinent named Valbaara surrounded by the superocean Nealbara. It consisted of all the continents perfectly fitted together into one whole piece. Through the eons, the supercontinent and superoceans have changed shapes and hence adopted names from Rodinia, Columbia and many more. The most recent one, Pangea (translating to ‘all of Earth’ in Ancient Greek), which also had the good fortune of sheltering the Jurassic community, was hit on the Yucatan Peninsula by a meteor, triggering the mass-extinction event of the dinosaurs. The continents, since then, have been drifting apart in the Panthalassa, Pangea’s superocean. Now the landmasses are starting to move back in and in 200 million years are predicted to form the first major supercontinent in a while. 


Continental drift has interestingly nothing to do with the tidal forces of the Sun and Moon. It is all dependent on the movement beneath the lithosphere. The asthenosphere harbors convectional currents due to the heat from the core and the colder temperature on the lithosphere’s side. The conventional currents shift the land masses above and the continental plates, subsequently shift, either converging, sliding past or diverging with each other. The Himalayan Mountains are a result of the independent Indian Plate converging into the Euroasian Plate, initially floating towards the target at a rate of 9 to 16 centimeters per year. In this case, the Indian Plate slid beneath the Eurasian Plate accreting wedged off rock and uplifting the Eurasian Plate to create the Himalayan Range at the point of collision, halting the volcanic activity on the Tibetan Plateau in the process. To this day, the Indian Plate has been advancing further north allowing an increase of 1 to 2 inches in the height of Mount Everest.


A map of Earth's crustal plates, their features and their direction of continental drift


When plates slide past each other they grind together, creating pressure that eventually gives out in the form of earthquakes. Sliding by creates faults, fissures and rifts in the earth like the San Andreas Fault Line, transforming into a source of frequent earthquakes.  Diverging on the other hand open ups rifts in the land which is filled by the leaked mantle when it solidifies on the surface. That is why the Himalayas are not the tallest or largest mountains in the world. They are overtaken by the Mid-Atlantic Ocean Range, an underwater range covering the entire Atlantic floor, which is the result of heavy divergence and constant spilling out of the solidified mantle. Tsunamis like that from the Tohoku Earthquake are a result of plate divergence too and seeing the consequences of such disasters, the need to have a better understanding about their causes is direr than ever.


Above: The mechanism and types of crustal movements. Different drifts produce different features. The Pacific Basin between the Eurasian Plate and the North American Plate is called the Ring of Fire, owing to 75% of the world’s active and dormant volcanoes being situated their as a result of collision of the number of plates beneath the Pacific Ocean.


The observance of Alfred Wegener was a life-saver, allowing pattern based analysis which has saved many lives from natural disasters like volcanic eruptions and earthquakes. The M8 algorithm for earthquake predictions is only one example of how scientists have quantified the pattern of continental drift. Gradual plate movement has literally changed the shape of the world and for better or for worse it will continue to do so, without our consent.



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