The Science of Plate Tectonics

According to ENCYCLOPAEDIA BRITANNICA, "Plate tectonics is the theory of the dynamics of Earth’s lithosphere as well as the evolution of Earth’s surface and reconstruction of its past continents and oceans."

It deals with the large-scale movement of the partitions of Earth's lithosphere, which is the combination of upper mantle and crust. These processes began when Earth cooled down after its formation 3.5 billion years ago. This is the reason why a super-continent like Pangaea drifted to form the 7 continents that are existing today. The plate moves towards and away from each other with an annual relative movement ranging from 0 to 160 mm.

The crust is the thin outer layer of earth's surface ranging from 7-50 kilometers in thickness. It can either be oceanic or continental, consisting of wide range of mineral deposits, ores and elements. The thickest layer of earth's surface is called the mantle, with almost the depth of 2900 kilometers. It consists of two layers, upper and lower, separated by the Transition zone. It is mostly made up of molten semi-solid slowly flowing magma, rich in mineral content.

These tectonic plates are made of oceanic and thicker continental lithosphere. This layer is hard, cool with higher mechanical strength. Below this layer lies the asthenosphere, which comprises the upper mantle. Hence the asthenosphere is hotter and flows more easily than lithosphere. The asthenosphere has variations in depth, constitution and density at each point due to slow creeping movement. Both of these layers transfer heat, former by conduction and latter by convection. The mantle and crust can belong to either depending on temperature, pressure, and depth.

The asthenosphere has molten magma consisting of minerals and elements which gets churned and toiled up and down the mantle. This is called the convection cell, where this hot molten goo is turned over and over again slowly. The heat is transferred from the interior of earth's surface, the core to the crust. When this heat reaches the bottom surface of the crust, it finds a way to escape out of the surface. This forms different kinds of plate boundaries. The hot molten goo turns parallel to the crust's surface, sideways and moves in that direction before falling back to a region called the subduction zone. In this region, one of the plates slides beneath the other causing the crust to pull down behind it. This causes the movement of plates.

Credits, Wikimedia Commons

Boundaries

Conservative: When two plates meet and grind past one another no geographic feature is created, rather a fault line is given birth. Neither of these plates is destroyed in this process. A fault line causes constant earthquakes to arise in that area due to discontinuous weak geographic base unable to sustain the energy release of the plate movement. San Andreas is fault region formed by the conservative boundary. Divergent: When two plates move away from each other, a ridge forms between them, thus a canyon is developed. It occurs either in ocean basin or land. Mostly at ocean basin, underwater earthquakes, or ocean fills the ridge with sand from the seabed. East African Rift is an example formed due to divergent boundaries. Convergent: When two plates move towards each other, collision causes a geographic feature like subduction zone or continental plateau or mountain. The Himalayas, Ural mountains, etc are the result of convergent plates.

Credits, Wikimedia Commons

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Citations: Seen: 03-04-2018

www.bbc.co.uk - Plate tectonics

Plate tectonics | Theory, Facts, & Evidence | Britannica.com

What is Plate Tectonics? | Live science.com

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