In this chapter we will learn about major physical features of India and how they have been formed.
- India has practically all major physical features of the earth. Explain.
- Why is the color of soil different at different places?
The color of soil varies from one place to the other because soil is formed out of different types of rocks that get their colors due to the differences in rock formations.
- What are geological periods? How have geological periods influence India’s reliefs?
- Geological periods are spans of time during which the earth undergoes various changes.
- India is a large landmass formed during different geological periods which has influenced its relief.
- What is relief?
Relief is the difference in height from the surrounding terrain.
- What are the processes that have created and modified the relief to its present form?
- What is the Theory of Plate Tectonics?
- The The Theory of Plate Tectonics explains the formation of the earth’s physical features with the help of some theories based on certain evidences.
- According to this theory, the crust (upper part) of the earth has been formed out of seven major and some minor plates.
- The movement of the plates results in the building up of stresses within the plates and the continental rocks above, leading to folding, faulting and volcanic activity.
- Broadly, these plate movements are classified into three types.
- While some plates come towards each other and form convergent boundary, some plates move away from each other and form divergent boundary.
- In the event of two plates coming together they may either collide and crumble, or one may slide under the other.
- At times, they may also move horizontally past each other and form transform boundary.
- The movement of these plates have changed the position and size of the continents over millions of years.
- Such movements have also influenced the evolution of the present landform features relief of India.
- The oldest landmass, (the Peninsula part), was a part of the Gondwana land.
- The Gondwanaland included India, Australia, South Africa and South America as one single land mass.
- The convectional currents split the crust into a number of pieces, thus leading to the drifting of the Indo-Australian plate after being separated from the Gondwana land, towards north.
- The northward drift resulted in the collision of the plate with the much larger Eurasian Plate.
- Due to this collision, the sedimentary rocks which were accumulated in the geosyncline known as the Tethys were folded to form the mountain system of western Asia and Himalaya.
- The Himalayan uplift out of the Tethys sea and subsidence of the northern flank of the peninsular plateau resulted in the formation of a large basin.
- How were the northern plains of India formed?
- In due course of time this depression, gradually got filled with deposition of sediments by the rivers flowing from the mountains in the north and the peninsular plateau in the south.
- A flat land of extensive alluvial deposits led to the formation of the northern plains of India.
- The land of India displays great physical variation. Geologically, the Peninsular Plateau constitutes one of the ancient landmasses on the earth’s surface.
- It was supposed to be one of the most stable land blocks. The Himalayas
and the Northern Plains are the most recent
landforms. From the view point of geology,
Himalayan mountains form an unstable zone.
The whole mountain system of Himalaya
represents a very youthful topography with
high peaks, deep valleys and fast flowing rivers.
The northern plains are formed of alluvial deposits. The peninsular plateau is composed
of igneous and metamorphic rocks with gently
rising hills and wide valleys.
Major Physiographic Divisions of India
The physical features of India can be grouped under the following physiographic divisions.
- The Himalayan Mountains
- The Northern Plains
- The Peninsular Plateau
- The Indian Desert
- The Coastal Plains
- The Islands.
The Himalayan Mountains
- The Himalayas, geologically young and structurally fold mountains stretch over the northern borders of India. These mountain ranges run in a west-east direction from the Indus to the Brahmaputra. The Himalayas represent the loftiest and one of the most rugged mountain barriers of the world. They form an arc, which covers a distance of about 2,400 Km. Their width varies from 400 Km in Kashmir to 150 Km in Arunachal Pradesh.
- The altitudinal variations are greater in the eastern half than those in the western half.
- The Himalaya consists of three parallel ranges in its longitudinal extent. A number of valleys lie between these ranges. The northern most range is known as the Great or Inner Himalayas or the ‘Himadri’. It is the most continuous range consisting of the loftiest peaks with an average height of 6,000 metres. It contains all the prominent Himalayan peaks.