LESSON 15: PLATE TECTONICS
Plate tectonics is the twisting, bending and breaking of the crust and its rocks as a result of plate movements
This theory describes the constant movement of the earth crust, according to this theory; the earth crust is made up of segment called PLATES which lies over the mantle. The theory of plate tectonics was derived from the proofs of continental drift in the 1960s
Plates are righted blocks that make up the earth crust which are constantly moving at a rate of 1 to 2 millimeter a year. These plates are divided into 2 namely; OCEANIC PLATE and CONTINENTAL PLATE
PLATE MARGINS AND MAIN LANDFORMS
During plate motion some plates converge or move toward each other, others move away from each other or diverge while others by pass each other. The crustal zone where 2 plates make a contract is called a PLATE MARGIN OR PLATE BOUNDARY.
- Constructive plate margin:
These are areas on the earth crust where 2 plates move away from each other. When 2 plates diverge, a new crust is formed thus the name constructive plates margin E.G The boundary btw the Nazca plate and the pacific plate.
- Destructive plate margins:
They are formed where plates moving towards each others are colliding. It is called destructive bcs the crystal rocks are destroyed as 2 plates meet each other E.G The zone btw Nazca and South America plate landform here are deep sea trenches, fold mount.
- Conservative plate margins:
This are zone on the earth surface where 2 plates move parallel to each other without creating nor destroying crustal rocks E.G plate btw North America plate and the Pacific plate features here are Tear fault