Basic Geography/Plate Tectonics

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The Earth's Crust is not a an unbroken shell, evidences are there that it is rather made up of about a dozen large block and about three more dozens smaller ones, called plates. These plates are changing their positions, though very slowly, with respect to each other and to the inner parts of the Earth. The scientific theory describing the motion of the plates, its probable causes and consequences is termed as Plate Tectonics.