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In this article we are discussing the Earth’s interior.

Theory of tectonic plates:

a) In 1967, Daniel McKenzie, Bob Parker and Jason Morgan discovered the theory of plate tectonics stating that the Earth’s crust is broken up into plates. 

b) A tectonic plate (also known as lithospheric plate) is a huge, irregularly shaped slab of solid rock, mostly composed of both continental & oceanic lithosphere.

c) These plates move horizontally over the asthenosphere as rigid units. 

d) Based on size, there are 2 types of plates.  Major plates have an area higher than 10 million km2 whereas minor plates are less than 10 million km2 in area but more than 1 million km2. 

e) There are 7 major plates and some minor plates. Major plates are surrounded by young fold mountain ridges, trenches and /or faults.

List of major plates:

a) Antarctica and the surrounding oceanic plate

b) North American (with the western Atlantic floor separated from the South American plate along the Caribbean islands) plate

c) South American (with western Atlantic floor separated from the North American plate along the Caribbean islands) plate

d) Pacific plate

e) India-Australia-New Zealand plate

f) Africa with the eastern Atlantic floor plate

g) Eurasia and the adjacent oceanic plate

Minor plates:

a) Cocos plate : Between Central America and Pacific plate

b) Nazca plate : Between South America and Pacific plate

c) Arabian plate : Mostly the Saudi Arabian landmass

d) Philippine plate : Between the Asiatic and Pacific plate

e) Caroline plate : Between the Philippine and Indian plate (North of New Guinea)

f) Fuji plate : North-east of Australia

According to German meteorologist Alfred Wegener, the continents do not move but plates move constantly over the globe and have been throughout the history of the Earth.

He also stated that all the continents have initially existed as a supercontinent in the form of Pangaea/Pangea. Later, it was discovered that the continental masses on the plates have been wandering all through geological period.

Position of the Indian subcontinent (mainly peninsular India) is traced with the help of rocks analysed from the Nagpur area.

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