What Is Tectonic Plates | Number Of Tectonic Plates In Earth
1. What Is Tectonic Plates
2. Number Of Tectonic Plates In Earth
3. Two Types Of Tectonic Crust
Plate tectonics is a scientific theory that explains the large-scale motions in the Earth’s lithosphere. It also attempts to explain the formation of surface relief in the form of continents, oceans and mountains and the geographical distribution of phenomena such as earthquakes and volcanoes.
What Is Tectonic Plates
This theory evolved from a concept called continental drift, designed in the first decade of the twentieth century, when new evidence was discovered in the 1960s that strengthened the concept of continents being dynamic rather than stationary.
The most important of this evidence is the evidence related to palaeomagnetism, which confirmed the ocean floor expansion. The exposition of this theory is considered to have started with the discovery of ocean floor variance by Harry Hess. And scholars like Wilson, Morgan, Mackenzie, Oliver, Parker etc. contributed to its promotion by providing evidence in its favor.
According to this theory, the upper layer of the Earth, about 80 to 100 km thick, called the lithosphere, and which includes part of the crust and upper part of the mantle, [What Is Tectonic Plates] is broken into many pieces called plates. These plates are floating on the semi-molten layer of the asthenosphere below and are generally moving at a speed of about 10-40 mm/yr, although some of them have speeds of up to 160 mm/year.
Due to the movement of these plates, the origin of the present surface form of the earth and the explanation of mountain formation is presented and it has also been seen that earthquakes often come only on the boundaries of these plates and volcanoes are also found on these plate boundaries.
Number Of Tectonic Plates In Earth
According to this theory, the lithosphere that forms the Earth’s upper crust, which includes the crust and part of the upper mantle, is divided into several pieces called plates. Generally the number of larger plates in these plates is assumed to be 6. Apart from this, there are also some medium and small sized plates. Following is a list of them.
- African Plate:- A major tectonic plate underlying Africa west of the East African Rift – 61,300,000 km2
- Antarctic Plate:- A tectonic plate containing the continent of Antarctica and extending outward under the surrounding oceans – 60,900,000 km2
- Eurasian Plate:- A tectonic plate which includes most of the continent of Eurasia – 67,800,000 km2
- Indo-Australian Plate:- A major tectonic plate formed by the fusion of the Indian and Australian plates 58,900,000 km2 often considered two plates:
- Australian Plate:- A major tectonic plate, originally a part of the ancient continent of Gondwana – 47,000,000 km2
- Indian Plate:- A minor tectonic plate that got separated from Gondwana – 11,900,000 km2
- North American Plate:- Large tectonic plate including most of North America, Greenland and part of Siberia. – 75,900,000 km2
- Pacific Plate:- An oceanic tectonic plate under the Pacific Ocean – 103,300,000 km2
- South American Plate:- Major tectonic plate which includes most of South America and a large part of the south Atlantic – 43,600,000 km2
Two Types Of Tectonic Crust
It is now known that there are two types of crust on Earth, continental crust and oceanic crust, with the former having a different composition and lighter in origin, both of which lie on a deeper liquefied cover. In addition, oceanic crust is still forming at the spreading centers, and this, along with the subduction, drives the plate system in a disorderly fashion, resulting in continuous orogeny and isostatic imbalance.
[What Is Tectonic Plates]