Outer mantel of the earth sit's on the plate called tectonic plates .this plats is moving constantly .if u see the world map u will find out that continent is like pussel chips u r rearrange it and joint it .before separation of the continent it is called as pangea .

         this plates r moving with the help of the fault zone(lava"sambar" guessing area) .earth quack occurs mainly due to this plate movement  
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The theory of tectonic plates refer to the movement of the plates in the earth's surface.