Physical Features of India

India is home to all the major geographical features, including mountains, plains, deserts, plateaus, and islands. India exhibits a wide range of physical characteristics. Geographically, the Peninsular Plateau is one of the oldest landmasses on the earth's surface. The most recent landforms are the Northern Plains and the Himalayas. The northern plains are formed of alluvial deposits.

1.0Introduction

India is a large nation with a variety of topography. What type of environment do you reside in? The wide expanse of plain land is familiar to many who reside on the plains. On the other hand, if you reside in a hilly area, you are likely to see rocky landscapes with valleys and mountains. Tall Himalayan peaks, lush northern plains, coastal plains on the country's east and west coasts, the peninsular plateau in the south, and two island groups in the Arabian Sea and Bay of Bengal are all part of India. Earth's scientists have sought to explain the formation of physical features using several theories, one of which is the "Theory of Plate Tectonics".

2.0Theory of Plate Tectonics

There was only one enormous supercontinent called Pangaea and one ocean called Panthalassa surrounding Earth approximately 300 million years ago, instead of the current seven continents.

The present theory of plate tectonics, which holds that the Earth's outer shell is divided into many plates that slide over the rocky mantle, was introduced with the explanation of Pangaea's creation.

According to the theory of plate tectonics, the lithosphere, or solid outer crust of the Earth, is divided into plates that move across the asthenosphere, or molten upper mantle. Oceanic and continental plates come together, spread apart, and interact at boundaries all over the planet.

Indo-Australian Plate Collided with Eurasian Plate There are three types of plate boundaries. They are: Divergent Boundaries: The plates separate from one another, generating new crust. Spreading sites are locations when plates diverge from one another.

Divergent

Convergent Boundaries: The earth's crust is destroyed when one plate subducts under another. The place where the plate sinks is called a subduction zone. Convergence can happen in three ways. These are:

• Between an oceanic and continental plate.
• Between two oceanic plates; and
• Between two continental plates.
  
  Convergent

Transform Boundaries: The earth's crust is neither created nor destroyed because the plates slide past each other horizontally.

Due to these tectonic movements and collision, physical features like Himalayas and Northern plains were formed.

3.0Major Physiographic Divisions

The physical features of India can be grouped under the following physiographic divisions. (a) The Himalayan Mountains (b) The Northern Plains (c) The Peninsular Plateau (d) The Indian Desert (e) The Coastal Plains (f) The Islands

The Himalayan Mountains

Geologically young and structurally fold mountains stretch over the northern borders of India. Run in a west-east direction from the Indus to the Brahmaputra. Represents the tall high and one of the most rugged mountain barriers of the world. They form an arc, which covers a distance of about $2,400\mathrm{Km}$. 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 Himalayas consist of three parallel ranges in its longitudinal extent.

(i) Himadri or Inner Himalayas

(ii) Himachal or lesser Himalaya

(iii) Shiwaliks

Division of Himalayas on the basis of regions from west to east, demarcated by the rivers

Physical Features of India

Division of Himalayas (West to East) demarcated by Rivers

Beyond the Dihang gorge, the Himalayas bend sharply to the south and spread along the eastern boundary of India. They are known as the Purvanchal or the Eastern hills.

The Northern Plain

(i) It has been formed by the interplay of the three major river systems, namely- the Indus, the Ganga, and the Brahmaputra along with their tributaries. (ii) It is formed of alluvial soil. (iii) It spreads over an area of 7 lakh sq. km. (iv) The plain being about 2400 Km long and 240 to 320 Km broad, is a densely populated physiographic division and is agriculturally a very productive part of India. (v) The rivers coming from northern mountains are involved in depositional work. In the lower course, due to gentle slope, the velocity of the river decreases which results in the formation of riverine islands. (Majuli is the largest inhabited riverine island in the world in the Brahmaputra River, Assam) The rivers in their lower course split into numerous channels due to the deposition of silt. These channels are known as distributaries.

The Northern Plain is broadly divided into three sections. (i) The Western part of the Northern Plain is referred to as the Punjab Plains. Formed by the Indus and its tributaries, the larger part of this plain lies in Pakistan. The Indus and its tributaries-the Jhelum, the Chenab, the Ravi, the Beas, and the Sutlej originate in the Himalaya. This section of the plain is dominated by the doabs.

(ii) The Ganga plain extends between Ghaggar and Teesta rivers. It is spread over the states of North India, Haryana, Delhi, U.P., Bihar, partly Jharkhand and West Bengal to its East. (iii) In Assam lies the Brahmaputra plain and extends from Paschim banga, through Assam and Bangladesh to India's eastern border.

According to the variations in relief features, the Northern plains can be divided into four regions -

(ii) South of this belt, the streams and rivers re-emerge and create a wet, swampy, and marshy region known as Terai. This was a thickly forested region full of wildlife. The forests have been cleared to create agricultural land and to settle migrants from Pakistan after partition.

(iii) The largest part of the northern plain is formed of older alluvium. They lie above the flood plains of the rivers and present a terrace like feature. This part is known as Bhangar.

(iv) The soil in this region contains calcareous deposits locally known as Kankar. The newer, younger deposits of the flood plains are called Khadar. They are renewed almost every year and so are fertile, thus, ideal for intensive agriculture.

Northern Plains

• Indus
• Ganga
• Brahmaputra
• Formed due to deposition of Alluvium in the vast basin at foothills of Himalayas. Soil type: Alluvial Area Covered: 7 lakh sq.km ( 2400 km long & 240 to 320 km broad). Importance: Agriculturally productive & densely populated. Work done by rivers: Formation of riverine Islands & split into numerous channels known as distributaries. Divisions:
• Western Part: Indus plain (large part in Pakistan)
• Central & Eastern Part: Ganga plain between Ghaggar & Teesta rivers.
• Eastern Part: Brahmaputra plain to India's Eastern borders
  
  According to the variations in relief features

4.0The Peninsular Plateau

A tableland composed of the old crystalline, igneous and metamorphic rocks, formed due to the breaking and drifting of the Gondwana land and thus, making it a part of the oldest landmass. The plateau has broad and shallow valleys and rounded hills.

This plateau consists of two broad divisions-

(i) The Central Highlands - Malwa plateau and Chhota Nagpur Plateau together are called Central Highlands. It lies to the north of the Narmada River covers a major area of the Malwa plateau. The Vindhyan range is bounded by the Central Highlands on the south and the Aravalis on the northwest. The further westward extension gradually merges with the sandy and rocky desert of Rajasthan.

• The flow of the rivers draining this region, namely the Chambal, the Sind, the Betwa and Ken is from southwest to northeast, thus indicating the slope.
• The Central Highlands are wider in the west but narrower in the east. The eastward extensions of this plateau are locally known as the Bundelkhand and Baghelkhand. The Chotanagpur plateau marks the further eastward extension, drained by the Damodar River. (ii) The Deccan Plateau is a triangular landmass that lies to the south of the river Narmada. The Satpura range flanks its broad base in the north while the Mahadev, the Kaimur hills and the Maikal range from its eastern extensions.
• The Deccan Plateau is higher in the west and slopes gently eastwards. An extension of the Plateau is also visible in the northeast-locally known as the Meghalaya, KarbiAnglong Plateau and North Cachar Hills. It is separated by a fault from the Chotanagpur Plateau.
• Three prominent hill ranges from the west to east are the Garo, the Khasi and the Jaintia Hills.

The Western Ghats and the Eastern Ghats mark the western and the eastern edges of the Deccan Plateau, respectively. Western Ghats lie parallel to the western coast. They are continuous and can be crossed through passes only. The Western Ghats are higher than the Eastern Ghats. Their average elevation is 900-1600 metres as against 600 metres of the Eastern Ghats. The Eastern Ghats stretch from the Mahanadi Valley to the Nigiris in the south. The Eastern Ghats are discontinuous and irregular and dissected by rivers draining into the Bay of Bengal. The Western Ghats cause orographic rain by facing the rain bearing moist winds to rise along the western slopes of the Ghats. The Western Ghats are known by different local names. The height of the Western Ghats progressively increases from north to south. The highest peaks include the Anai Mudi ( 2,695 metres) and the Doda Betta ( 2,637 metres). Mahendragiri ( 1,501 metres) is the highest peak in the Eastern Ghats. Shevroy Hills and the Javadi Hills are located to the southeast of the Eastern Ghats.

The Indian Desert

The Indian desert lies towards the western margins of the Aravali Hills. It is an undulating sandy plain covered with sand dunes. This region receives extremely low rainfall below 150 mm per year. It has arid climate with low vegetation cover. Streams appear during the rainy season. Soon after they disappear into the sand as they do not have enough water to reach the sea. Luni is the only large river in this region. Barchans (crescent shaped dunes) cover larger areas, but longitudinal dunes become more prominent near the Indo-Pakistan boundary.

The Coastal Plains

The Peninsular plateau is flanked by stretch of narrow coastal strips, running along the Arabian Sea on the west and the Bay of Bengal on the east. The western coast, sandwiched between the Western Ghats and the Arabian Sea, is a narrow plain. It consists of three sections. The northern part of the coast is called the Konkan (Mumbai - Goa), the central stretch is called the Kannad Plain while the southern stretch is referred to as the Malabar coast. The plains along the Bay of Bengal are wide and level. In the northern part, it is referred to as the Northern Circar, while the southern part is known as the Coromandel Coast. Large rivers such as the Mahanadi, the Godavari, the Krishna, and the Kaveri have formed extensive delta on this coast. Lake Chilika is an important feature along the eastern coast.

The Islands

(i) Lakshadweep Islands group lies close to the Malabar coast of Kerala. This group of islands is composed of small coral islands. Earlier they were known as Laccadive, Minicoy, and Amin dive. In 1973 these were named as Lakshadweep. It covers small area of $32\mathrm{sq}.\mathrm{km}$. Kavaratti Island is the administrative headquarters of Lakshadweep. This island group has great diversity of flora and fauna. The Pitti island, which is uninhabited, has a bird sanctuary.

Andaman and Nicobar Islands

5.0Influence of physical features

Each region complements the other and makes the country richer in its natural resources. The mountains are the major sources of water and forest wealth. The northern plains are the granaries of the country. They provide the base for early civilisations. The plateau is a storehouse of minerals, which has played a crucial role in the industrialisation of the country. The coastal region and island groups provide sites for fishing and port activities. Thus, the diverse physical features of the land have immense future possibilities of development.

Coral Polyps

Coral polyps are short-lived microscopic organisms, which live in colonies. They flourish in shallow, mud free and warm waters. They secrete calcium carbonate. The coral secretion and their skeletons from coral deposits in the form of reefs they are mainly of three kinds : Barrier Reef, Fringing Reef, and Atolls. The Great Barrier Reef of Australia is a good example of the first kind of coral reefs. Atolls are circular or horseshoe shaped coral reefs.

6.0Glossary

• Tarai Zone- It is a Zone next to the bhabar which is wet and marshy. It has a thick forest cover and a variety of wildlife.
• Tributary- A river that joins the main river and increases the volume of water.
• Plate Tectonic- The scientific concept which explains the movements of the different plates of the crust of the earth.
• Gondwana land- A major portion of the crust that once incorporated Australia, Peninsular India, South Africa, and South America.
• Tethys Sea - A narrow sea with a sinking bottom lying between Gondwana land in the south and Angara land in the north.
• Flood Plain- A plain formed by the sediment deposited by the rivers years after year.
• Pass- A gap in mountain range providing a natural route across.
• Gorge- The steep-sided narrow and deep valley of a river formed in its upper course is termed as a Gorge or a Canyon. It is also called an I shaped valley.