Plate Tectonics

The Theory of Plate Tectonics:


Plates-  Irregularly shaped slabs that fit together like paving stones to form the surface layer of the Earth.

Tectonics refers to the branch of geology that deals with the movements that shape the Earth's crust.  The topmost solid part of the Earth (the lithosphere), which consists of crust, and a thick layer of relatively cool, rigid mantle rock are made up of a number of plates. Plates move at different speeds and in different directions. Plates usually contain both oceanic and continental crust.

The Theory of Plate Tectonics, explains how the Earth has evolved over time. It helps to explain the formation and destruction of the Earth's crust and its movements and collisions.

There are seven major lithospheric plates. The largest plate is the Pacific Plate, which covers one-fifth of the Earth's surface. The other major plates are the North American, South American, Eurasian, African, Indo-Australian and Antarctic plates. There are also many smaller plates.

Most plate boundaries are on the ocean floor.

1)  Divergent boundaries are formed by the mid-ocean ridges.

     (The plates move apart)


2)  Convergent boundaries are formed by the trenches. 

     (The plates move toward each other)


3)  Strike-slip boundaries are formed by the lateral faults at which two plates

     slide horizontally past each other. 


(example: the San Andreas Fault)