Structure and relief UPSC | Geography of India| Geography Optional Paper 2

Table of Contents:

• What is Geological Structure?
• Geological History of India
• Geological division of India
• Peninsular India
• Himalayan Mountains
• Northern Plain
• The geological timescale of India
• Geological Structure of India
• Relief of India

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What is the Geological Structure?

Geological structure means the arrangement and deposition of rocks over a geological timescale.

The geological time scale of rocks means chronological dating of rocks.

Geological History of India:

• 250 million years ago, there was a supercontinent Pangeas.
• 200 million years ago, in Triassic time, Pangaea broke out into two parts; Laurasia( in the north) and Gondwanaland( in the south).
• The oldest landmass peninsula India was part of Gondwanaland land that include India, Australia,  Africa, Madagascar, South America, Antarctic.
• Due to convection current, the Gondwanaland landmass breaks up into many parts of about 140 million years ago in Jurassic time.
• India and Australia got separated from Gondwanaland.
• Later It also broke out into a two-part India plate moves north and the Australia plate moves south.
• 80 Million years ago India is about 6400 km from the current position 
• About 50 million years ago, Indian plates collides with Eurasian plates.
• Due to the collision of the Indian plate into Eurasian plates. Sedimentary rocks are accumulated in the geosyncline area that is Tethys sea and Himalayan mountain created on Tethys sea.
• The northern part of the peninsula subsidies under Eurasian plates and large basins are created. Over time it gradually filled by river sediments and great northern Indian plain developed.

Geological Division of India:

On the basis of geological history, there is three-part of India:

• Peninsular plateau( Pre-Cambrian Period; 4000 million to 541 million) 
• Himalayan range( Tertiary Period; after Extinction of Dinosaur; less than 50 million years old.)
• Northern Indian Plain ( quaternary Period)

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Geological structure of India

Peninsular India:

• The oldest stable landmass of the Pre-Cambrian or Azoic era(Non-living era); it is as old as earth crust; It is made up of Igneous and metamorphic rocks with gently rising hills and wide valley.
• It bordered by Kachchh, Aravali range near Delhi, parallel to Ganga and Yamuna. The extension of the peninsula is found as the Meghalaya plateau.
• Some vertical movement and created block faulting.
• For example, 
• the rift valley of Narmada, Tapi, and Mahanadi, Satpura block.

Northern Indian plains:

• It is formed by sedimentary deposits of alluvial soil that is deposited by the Himalayan drainage system.
• It lies between the Himalayan in the north and peninsular India in the south.

Himalayan:

• It is formed by metamorphics and sedimentary ricks.
• We will discuss the relief feature of the Himalayan structure in the physiographic division of India's article.

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Geological Timescale of India

As per the geological survey of India, the country divides rocks into four major divisions:

• Archaean
• Purana
• Dravidian
• Aryan rock

It is further divided into many time; detail is mentioned in the below diagram;

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Geological Structure of India

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What is the relief?

Relief in particular areas means the highest and lowest elevation point of an area or vertical height from sea level.
For examples,

Relief of India:

• Highest point: k2: 8611 meters
• The lowest point; sea level
• Relief of India= 8611 meters

Himalayan relief:

• The altitudinal difference between the highest point of the mountain peak and the lowest point of the deep gorge valley.

For an explanation, please watch the below video:

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