Major Physiographic Divisions - Introduction

Major physiographic divisions

The physical features of India can be grouped under the following physiographic divisions (Figure 2.1):

Figure 2.1: Relief

1.  The Himalayan Mountains

2.  The Northern Plains

3.  The Peninsular Plateau

4.  The Indian Desert

5.  The Coastal Plains

6.  The Islands

The Himalayas

THE HIMALAYAN MOUNTAINS

The Himalayas

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 Himalayas consists of three parallel ranges in their 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 meters. It contains all prominent Himalayan peaks.

Figure 2.2: Himalayas

The folds of the Great Himalayas are asymmetrical in nature. The core of this part of the Himalayas is composed of granite. It is perennially snowing bound, and a number of glaciers descend from this range.

Table: Some Highest Peaks of the Himalayas

Himachal or Lesser Himalaya

THE HIMALAYAN MOUNTAINS

Himachal or Lesser Himalaya

The range lying to the south of the Himadri forms the most rugged mountain system and is known as Himachal or lesser Himalaya. The ranges are mainly composed of highly compressed and altered rocks. The altitude varies between 3,700 and 4,500 meters and the average width is 50 Km. While the Pir Panjal range forms the longest and the most important range, the Dhaula Dhar and the Mahabharat ranges are also prominent ones. This range consists of the famous valley of Kashmir, the Kangra and Kullu Valley in Himachal Pradesh. This region is well-known for its hill stations.

Figure 2.3: The Himalayas

The Shiwaliks

THE HIMALAYAN MOUNTAINS

The Shiwaliks

The outermost range of the Himalayas is called the Shiwaliks. They extend over a width of 10-50 Km and have an altitude varying between 900 and 1100 meters. These ranges are composed of unconsolidated sediments brought down by rivers from the main Himalayan ranges located farther north. These valleys are covered with thick gravel and alluvium. The longitudinal valley lying between the lesser Himalayas and the Shiwaliks is known as Duns. Dehra Dun, Kotli Dun, and Patli Dun are some of the well-known Duns.

Source: This topic is taken from NCERT TEXTBOOK

Regions from East to West

THE HIMALAYAN MOUNTAINS

Regions from East to West

Besides the longitudinal divisions, the Himalayas have been divided on the basis of regions from west to east. These divisions have been demarcated by river valleys. For example, the part of Himalayas lying between Indus and Satluj has been traditionally known as Punjab Himalaya but it is also known regionally as Kashmir and Himachal Himalaya from west to east respectively. The part of the Himalayas lying between Satluj and Kali rivers is known as Kumaon Himalayas. The Kali and Teesta rivers demarcate the Nepal Himalayas and the part lying between Teesta and Dihang rivers is known as Assam Himalayas. There are regional names also in these broad categories. Find out some regional names of the Himalayas

       The Brahmaputra marks the eastern-most boundary of the Himalayas. Beyond the Dihang gorge, the Himalayas bend sharply to the south and spread along the eastern boundary of India. They are known as the Purvachal or the Eastern hills and mountains. These hills running through the north-eastern states are mostly composed of strong sandstones, which are sedimentary rocks. Covered with dense forests, they mostly run as parallel ranges and valleys. The Purvachal comprises the Patkai hills, the Naga hills, the Manipur hills and the Mizo hills.

Mizo hills

The Northern Plain

THE NORTHERN PLAIN

The northern plain has been formed by the interplay of the three major river systems, namely — the Indus, the Ganga, and the Brahmaputra along with their tributaries. This plain is formed of alluvial soil. The deposition of alluvium in a vast basin lying at the foothills of the Himalaya over millions of years formed this fertile plain. It spreads over an area of 7 lakh sq. km. The plain being about 2400 km long and 240 to 320 km broad, is a densely populated physiographic division. With a rich soil cover combined with an adequate water supply and favorable climate, it is agriculturally a productive part of India.

The rivers coming from the northern mountains are involved in depositional work. In the lower course, due to a gentle slope, the velocity of the river decreases, which results in the formation of riverine islands.

The rivers in their lower course split into numerous channels due to the deposition of silt. These channels are known as distributaries.

Figure 2.5: The Northern Plains

Division of The Northern Plain

DIVISION OF THE NORTHERN PLAIN

The Northern Plain is broadly divided into three sections. 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 Satluj originate in the Himalayas. This section of the plain is dominated by the doabs.

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, particularly in Assam lies the Brahmaputra plain.

Source: This topic is taken from NCERT TEXTBOOK

Relief Features of Northern Plain

RELIEF FEATURES OF NORTHERN PLAIN

The northern plains are generally described as flat land with no variations in its relief. It is not true. These vast plains also have diverse relief features. According to the variations in relief features, the Northern plains can be divided into four regions. The rivers, after descending from the mountains deposit pebbles in a narrow belt of about 8 to 16 km in width lying parallel to the slopes of the Shiwaliks. It is known as bhabar. All the streams disappear in this bhabar belt. 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 the partition. Locate Dudhwa National Park in this region.

The largest part of the northern plain is formed of older alluvium. It lies above the floodplains of the rivers and presents a terrace-like feature. This part is known as bhangar. The soil in this region contains calcareous deposits, locally known as kankar. The newer, younger deposits of the floodplains are called khadar. They are renewed almost every year and so are fertile, thus, ideal for intensive agriculture.

More to know

*   Majuli, in the Brahmaputra river, is the largest inhabited riverine island in the world.

*   ‘Doab’ is made up of two words — ‘do’ meaning two and ‘ab’ meaning water. Similarly, ‘Punjab’, is also made up of two words — ‘Punj’ meaning five and ‘ab’ meaning water.

Source: This topic is taken from NCERT TEXTBOOK

The Peninsular Plateau

THE PENINSULAR PLATEAU

The Peninsular plateau is a tableland composed of the old crystalline, igneous and metamorphic rocks. It was 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, namely, the Central Highlands and the Deccan Plateau.

The Central Highlands

THE CENTRAL HIGHLANDS

The part of the Peninsular plateau lying to the north of the Narmada river, covering a major area of the Malwa plateau, is known as the Central Highlands. The Vindhyan range is bounded by the Satpura range 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 the 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.

Figure 2.6: A Waterfall in Chotanagpur Plateau

The Chotanagpur plateau marks the further eastward extension, drained by the Damodar river.

The Deccan Plateau

THE DECCAN PLATEAU

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 form its eastern extensions. Locate these hills and ranges in the Physical map of India. 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, Karbi-Anglong Plateau, and North Cachar Hills. It is separated by a fault from the Chotanagpur Plateau. Three prominent hill ranges from the west to the east are the Garo, the Khasi, and the Jaintia Hills.

The Western and Eastern Ghats

THE Western and Eastern Ghats

The Western Ghats and the Eastern Ghats mark the western and the eastern edges of the Deccan Plateau respectively. The Western Ghats lie parallel to the western coast. They are continuous and can be crossed through passes only. Locate the Thal, Bhor, and Pal Ghats in the Physical map of India.

The Western Ghats are higher than the Eastern Ghats. Their average elevation is 900– 1600 meters as against 600 meters of the Eastern Ghats. The Eastern Ghats stretch from the Mahanadi Valley to the Nilgiris 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 meters) and the Doda Betta (2,637 meters). Mahendragiri (1,501 meters) is the highest peak in the Eastern Ghats. Shevroy Hills and the Javadi Hills are located to the southeast of the Eastern Ghats. Locate the famous hill stations of Udagamandalam, popularly known as Ooty and the Kodaikanal.

Distinct Features

DISTINCT FEATURES

One of the distinct features of the Peninsular plateau is the black soil area known as Deccan Trap. This is of volcanic origin, hence, the rocks are igneous. Actually, these rocks have denuded over time and are responsible for the formation of black soil. The Aravali Hills lie on the western and northwestern margins of the Peninsular plateau. These are highly eroded hills and are found as broken hills. They extend from Gujarat to Delhi in a southwest-northeast direction.

The Indian Desert

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 very low rainfall below 150 mm per year. It has an 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.

Figure 2.7: The Indian Desert

Barchans (crescent-shaped dunes) cover larger areas but longitudinal dunes become more prominent near the Indo-Pakistan boundary. If you visit Jaisalmer, you may go to see a group of barchans. 

Source: This topic is taken from NCERT TEXTBOOK

The Coastal Plains

THE COASTAL PLAINS

The Peninsular plateau is flanked by a 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.

Figure 2.8: The Coastal Plains

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.

More to know

Chilika Lake is the largest saltwater lake in India. It lies in the state of Odisha, to the south of the Mahanadi delta.

Source: This topic is taken from NCERT TEXTBOOK

Lakshadweep Islands

LAKSHADWEEP ISLANDS

You have already seen that India has a vast mainland. Besides this, the country has two groups of islands. Can you identify these island groups?

Figure 2.9: An Island

Locate the Lakshadweep Islands group lying 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 Amindive. In 1973, these were named Lakshadweep. It covers a small area of 32 sq km. Kavaratti Island is the administrative headquarters of Lakshadweep. This island group has a great diversity of flora and fauna. The Pitti island, which is uninhabited, has a bird sanctuary.

Source: This topic is taken from NCERT TEXTBOOK

Andaman and Nicobar Islands

ANDAMAN AND NICOBAR ISLANDS

Now you see the elongated chain of islands located in the Bay of Bengal extending from north to south. These are Andaman and Nicobar Islands. They are bigger in size and are more numerous and scattered. The entire group of islands is divided into two broad categories – The Andaman in the north and the Nicobar in the south. It is believed that these islands are an elevated portion of submarine mountains. These island groups are of great strategic importance for the country. There is a great diversity of flora and fauna in this group of islands too. These islands lie close to the equator and experience an equatorial climate and have thick forest cover.

More to know

India’s only active volcano is found on Barren Island in the Andaman and Nicobar group of Islands.

Source: This topic is taken from NCERT TEXTBOOK

Highlights

HIGHLIGHTS

A detailed account of the different physiographic units highlights the unique features of each region. It would, however, be clear that 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.

Source: This topic is taken from NCERT TEXTBOOK