Plate tectonics Theory (PTT) UPSC ~ Civil Services Self Study

In 1967, McKenzie, Parker, and Margin gave the concept of plate tectonics.

What are tectonic plates?
A tectonic or lithosphere plate is a massive, irregular-shaped solid plate, that can be made of the only continent, only ocean, or both.

The most accepted theory explains the following phenomenon:

Present locations of the continents.
Cause and locations of volcanic eruption, earthquakes, tsunamis,
The process of mountain building.

Plate tectonics theory is based on three theories:

Continental drift theory
Seafloor spread theory
Conventional current cell

As per plate tectonics theory, the lithosphere ( crust+ upper part of the mantle) of the earth is divided into many segments called plates. The thickness of the plates varies from 80 to 100 km in the ocean and 100 to 200 km in the continents.

How many tectonic plates are there?

There are 13 plates on the earth, 7 are in large size and 6 are in small size. Large plates are:

Eurasian Plate
Indian Austral Plate
African Plate
North American Plate
South American Plate
Antarctic Plate
Pacific Plate:

At present the following events are happening due to plates movement:

The Atlantic Ocean is expanding
The Pacific Ocean is shrinking
The distance between New Delhi and Beijing is decreasing.

What are the 3 types of tectonic plate movement?

There are three types of interactions of plates that exist between plates in the plate tectonics theory.

The convergence or destructive boundary
Divergences or constructive boundary
Transverse boundary or no creation and destructive

Three types of tectonic boundaries

The convergence boundary:

When plates move towards each other, the heavy plate submerges under the lighter plate. The following are the types of convergence boundaries

Continent-Continent Convergence (C-C)
Ocean-Continent Convergence (O-C)
Ocean-Ocean Convergence (O-O)

Continent - Continent convergence(C-C):

The convergence of the Indian plate and the Eurasian plate is an example of C-C convergence. In this type of interaction, heavier continents' plates will be submerged. Since the continent plates are high in thickness hence volcanic activities can be rarely seen, however, at the boundary line earthquake, fold mountains, and landslides phenomenons are common.

Continent-Ocean convergence(C-O):

The conversion of the pacific ocean plate and the American plate is an example of the C-O boundary. Generally, ocean plates are heavier than continental plates, and the submergence of ocean plates happens in this case. At the boundary line, trench, volcanic mountain, and fold mountain, earthquakes, and landslides are common phenomena.

Ocean-ocean convergence (O-O):

In this case, two ocean plates converge and one of the heavy ocean plates submerges under the other. Volcanic activities and earthquakes are the common phenomena of this convergence. The ring of fire in the Pacific Ocean is an example of the O-O convergence.

Plate tectonics theory

The Divergence boundary:

When plates move away from each other than a divergence boundary is created.

The following are the types of divergence boundaries:

Continent-Continent divergence (C-C)
Ocean-Continent divergence (O-C)
Ocean-Ocean divergence (O-O)

Continent - Continent divergence(C-C):

The African rift valley is an example of a C-C divergence. In this type of movement, in the first phase crack happens in the boundaries line. In the second phase, the valley is created. In the later phase, the ocean is created.

Continent-Ocean divergence(C-O):

Expansion of the ocean can happen in this case.

Ocean -ocean divergence(O-O):

The Atlantic mid-ocean ridge is an example of the O-O divergence.

The transverse boundaries:

The transverse boundary is created when the plate slides each other without submergence and the creation of any plates. The alpine fault in New Zealand is an example of a transverse boundary.

Try to solve the following questions:

What is plate tectonics? how do plate movements transform the earth's crust? ( 25 Marks, 66th BPSC geography Optional Paper)
Bring about the basic difference between the drift theory and Plate tectonics. (UPPSC)
Critically examine plate tectonics and explain its relation to the evolution of major landform features on the surface of the earth. ( BPSC, 2019)
Describe the concept of plate tectonics and explain the effects of the collision of two similar and two dissimilar plates. ( UPPSC 2020)
State the concept of plate tectonics. How does it help in explaining the formation of the Himalayas and the Appalachian Mountains? (UPSC 2014, 250 words, 20 marks)

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