Scholars do not have a single opinion about the number of global plates, yet most have divided the entire earth surface into 6 large and 20 minor plates.
The description of the major plates is as follows:
1. Indian Plate: This plate comprises of the Indian subcontinent and the terrestrial crust of Australia, the Indian Ocean and the south western part of the Pacific.
2. Eurasian Plate: This is the only plate that is formed mostly from the continental crust. This plate extends from the mid – Atlantic ridges in the west, the Alps – Himalayan mountain range in the south and to the insular arc in the east.
3. African Plate: This is a mixed continental and oceanic plate. It extends to Antarctica in the south, to the Middle Atlantic ridge in the west and Eurasian Plate in the north.
4. American Plate: This includes the continental crust of the North and South America and the Oceanic crust extending from the east to the middle Atlantic Ridge. This plate extends to the west coast of continents and meets the Pacific Ocean plate. This plate is moving towards the west as a unit. As a result there are no tectonic motions on the eastern edges of the American continents.
5. Pacific Plate: From East Pacific Ridge to the West, it is the only plate extending across the Pacific Ocean that is fully formed from oceanic crust.
6. Antarctica Plate: Most of the Antarctica Plate is glaciated. This plate extends across the Atlantic continent to mid-ocean brackets.
Proof of plate tectonics: Evidences of plate tectonics include seamless variance, continental drift, widening of rift valleys, seismic incidents, volcanic activity, mountain formation process, island arcs.
Some of these are briefly described as follows:
1. Sea floor spreading: Flat spaces are formed in the opposite direction of two plates on the divergent edges. Magma rises above the convection function in these empty spaces, and the lava gets deposited above, which creates new styles. The continuation of this process keeps the order of forming the new shell crust. As a result, the ocean bottom is expanding.
2. Continental Drift: New discoveries related to continental drift – Pervasive and sea – level movements have strengthened the fact that the continents and ocean basins are never stable and permanent, which explains the flow of plates.
3. Broadening of Rift Valleys: The plates which cracked forming valleys on the edges, are becoming wider. The rate of expansion in the Red Sea and the Gulf of Aden is 1 cm per annum.
4. Other evidences include the creation of seismic incidents, volcanic activity, mountain formation, island arcs, and also evidence of plate morphology.
