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PLATE TECTONICS THEORY (PTT)

Plate Tectonics is . The old idea is

Continental Drift Theory. The concepts of Continental Drift and SFS (Sea Floor

Spreading) were combined into a much more encompassing theory called PTT. It

provides a framework from which most other geological processes can be viewed.

The hypothesis of Plate Tectonics Theory emerges from the fact that the

outer, rigid lithosphere of earth consists of several individual segments called Plates .

These plates vary in thickness from 80 -100 km in oceans to > 100 km in continents.

At places these may be as thick as 400 km.

PLATES AND THEIR MOTION

Total 12 plates in no.:

- Great Plates

- 6 of comparatively smaller size

Great Plates inc lude: -

1. Pacific Plate : Almost entirely oceanic plus small portion of California. Converging

in North and West. Movement: NW

2. American Plate : continental N & S America plus oceanic west of mid Atlantic

Ridge. For most of western edge, it is converging

3. Eurasi an Plate : largely continental plus fringed on east and north by oceanic.

Diverging on west and converging on east.

4. African Plate : continental core plus oceanic periphery.

5. Austral Indian : Mostly Oceanic plus Continental Aust. And peninsular India

6. Antarctic Plate : Antarctica continent surrounded by oceanic lithosphere. Almost

completely spreading all around.