Class 9 Social Science Physical Features of India Exam Notes

This Class 9 Social Science exam notes page on the Physical Features of India covers the formation of relief through plate tectonics, the formation of the Himalayas and the northern plains, the six physiographic divisions of India (Himalayan Mountains, Northern Plains, Peninsular Plateau, Indian Desert, Coastal Plains and Islands), the Bhabar, Tarai, Bhangar and Khadar belts, important rivers, deltas, plateaus and island groups, with a glossary and the chapter exercise.

FORMATION OF RELIEF / PHYSICAL FEATURES OF INDIA

India is made up of mountains, plains, plateaus, deserts and islands. The actions and reactions of many natural forces above and below the earth's crust, over millions of years, went into forming the present physical features of India. Some of these forces are earthquakes, volcanic eruptions, the heat of the sun and, above all, the movement of tectonic plates.

Earth scientists have attempted to explain the formation of physical features with the help of the Theory of Plate Tectonics. According to this theory, the crust (upper part) of the earth has been formed out of seven major plates and some minor plates.

Tectonic Plates
Due to the internal heat of the earth, currents of semi-molten rock move towards the crust and tear it apart, dividing it into large fragments called lithosphere or tectonic plates. There are seven major plates: South American, North American, Pacific, Indo-Australian, Eurasian, African and Antarctic.

Types of Plates
Tectonic plates are always moving in one direction or another. These movements are generally classified into three types:
(A) Diverging plates: If plates move away from each other, they are called diverging plates. The boundary they form is called a divergent boundary.
(B) Converging plates: If plates are pushed together, they are called converging plates. The boundary they form is called a convergent boundary.
(C) Transform plates: Sometimes converging plates neither collide nor slide under each other, but move horizontally past each other. Such plates are called transform plates, and the boundary they form is called the transform boundary.

Formation of the Himalayas
Geologists believe that where the Himalayas now stand, there was once a vast sea called the Tethys. All these changes were brought about by internal movements below the earth's crust and external forces acting on its surface. The Himalayas are also the result of these plate movements. The Indo-Australian plate separated from the supercontinent Gondwana land and drifted slowly north. It collided with the much larger Eurasian plate about 5 crore years ago. The northern edge of the Indo-Australian plate was pushed beneath the Eurasian plate. As a result of this collision, the sedimentary rocks of the enclosed ocean were folded to form the Himalayas and other mountain systems of western and central Asia.

Formation of the Northern Plains
The northern plains were formed through geological processes over different geological periods, together with weathering, erosion and deposition. Winds carved out rocks by weathering, while rivers carried out erosion and deposition over millions of years. The uplift of the Himalayas out of the Tethys Sea and the subsidence of the northern flank of the peninsular plateau formed a large basin. Over time this depression gradually got filled with sediments deposited by rivers flowing from the mountains in the north and the peninsular plateau in the south. The flat land of extensive alluvial deposits formed the northern plains of India.

The work of weathering by winds and of erosion and deposition by rivers is still going on, and the land is slowly advancing into the sea.

MAJOR PHYSIOGRAPHIC DIVISIONS OF INDIA

The major physical or physiographic divisions of India are:
1. The Himalayan Mountains
2. The Northern Plains
3. The Peninsular Plateau
4. The Indian Desert
5. The Coastal Plains
6. The Islands

THE HIMALAYAN MOUNTAINS

These fold mountains extend from Kashmir to Arunachal Pradesh in the north of India. They run in a west-east direction from the Indus to the Brahmaputra. Their length is about 2500 km and their width varies from 230 to 400 km. The Himalayas have three main divisions or ranges:
(A) The Great Himalayas or Himadri
(B) The Middle Himalayas or the Himachal
(C) The Lesser Himalayas or Shivalik Ranges

(A) The Great Himalayas or Himadri
These ranges are always snow-capped. They contain several high peaks that exceed 8000 metres above sea level. Mount Everest is the highest peak (8848 metres). Other high peaks include K2 (8611 metres), Kanchenjunga (8589 metres), Dhaulagiri (8172 metres), Nanga Parbat (8126 metres) and Annapurna (8078 metres). Because these ranges remain covered with snow, they are called Himadri. The Himalayas consist of three parallel ranges along their length, and a number of valleys lie between them. The core of this part of the Himalayas is composed of granite.

(B) The Middle Himalayas or the Himachal
These ranges lie below the Great Himalayas. Their altitude varies between 3700 and 4500 metres, with alternating ridges and valleys. The Kathmandu valley in Nepal and the Kashmir valley in India are the largest valleys in this region. The Pir Panjal range in Kashmir also belongs to this part of the Himalayas. These ranges are mainly composed of highly compressed and altered rocks.

(C) The Outer Himalayas or the Shivalik
These are the foothill ranges of the Himalayas. Their altitude varies between 900 and 1100 metres. They are often discontinuous and have gentle slopes towards the north and steep slopes towards the south. These ranges are made of unconsolidated material such as mud, silt and soft rock, and are prone to earthquakes and landslides. Some narrow valleys lie between the Shivalik and the Himachal ranges, called duns, for example Dehradun, Kotli Dun and Patli Dun.

Purvanchal or the Eastern Hills and Mountains
Beyond the Dihang gorge, the Himalayas bend sharply to the south and spread along the eastern boundary of India. These are known as the Purvanchal or the Eastern hills and mountains. The hills in the northeastern states are mostly composed of strong sandstones, which are sedimentary rocks. Covered with dense forests, they mostly run as parallel ranges and valleys. The Purvanchal comprises the Patkai hills, the Naga hills, the Manipur hills and the Mizo hills.

On the basis of location, the Himalayas can be divided as follows:
1. Western Himalayas (Punjab Himalayas): The western section lies between the Indus and the Satluj. It covers large parts of Jammu and Kashmir and a part of Himachal Pradesh. It is made up of the Ladakh, Zanskar and Pir Panjal ranges.
2. Central Himalayas: The section between the Satluj and the Kali is known as the Kumaon Himalayas. It extends through the state of Uttarakhand in India and Nepal.
3. Eastern Himalayas: The section between the Kali and the Teesta is known as the Nepal Himalayas.
4. Assam Himalayas: The section between the Teesta and the Dihang is known as the Assam Himalayas or Purvanchal. It is made up of the Patkai, Naga and Mizo hills, which are mainly composed of strong sandstones.

THE NORTHERN PLAINS

The plains have been formed by the interplay of three major rivers, the Indus, the Ganga and the Brahmaputra, along with their tributaries. The plain is formed of alluvial soil and spreads over an area of 7 lakh square km. It is about 2400 km long and 240 to 320 km broad. It is a densely populated physiographic division. With rich soil, adequate water supply and a favourable climate, it is an agriculturally very productive part of India.

The rivers coming from the northern mountains are involved in depositional work. In the lower course, the gentle slope reduces the velocity of the river, which results in the formation of riverine islands. In their lower course, rivers split into numerous channels due to the deposition of silt. These channels are known as distributaries. The vast plain can be subdivided as follows:

(A) The Indus River Basin: This region is drained by the Indus and its tributaries, the Jhelum, Chenab, Beas, Ravi and Satluj. The Satluj also rises in the Himalayas. The waters of these rivers flow into the Arabian Sea. The Punjab plains are formed by the five main tributaries of the Indus, hence the name Punjab, meaning the land of five rivers. This section of the plains is dominated by doabs.

(B) The Ganga-Brahmaputra Basin: The Ganga enters the northern plains at Haridwar and flows eastward. On its way to the sea, it is joined by many tributaries from both the north and the south. It is joined by the Brahmaputra in Bangladesh. The Brahmaputra enters India in Arunachal Pradesh. It flows south for a while, then turns west across Assam, and on reaching Bangladesh turns south again. The joint stream of the Ganga and the Brahmaputra flows as the Meghna and drains into the Bay of Bengal. The Ganga-Brahmaputra delta (the Sundarbans) is the world's largest and fastest-growing delta.

On the basis of differences in relief, the plain is divided into (1) Bhabar, (2) Tarai, (3) Bhangar and (4) Khadar.

(1) Bhabar: A narrow belt covered with pebbles that lies along the foot of the Shiwaliks from the Indus to the Teesta. It is laid down by numerous streams descending from the hills. The pebbly beds are parallel to the slope of the river bed. This belt is about 8 to 16 km wide.
(2) Tarai: South of the Bhabar belt, the streams and rivers re-emerge and create a wet and marshy area. It has thick forest and a variety of wildlife.
(3) Bhangar: Composed of old alluvium. It is formed on the higher parts of the plains of rivers and presents a terrace-like feature. It is less fertile than the Khadar. The soil in this region contains calcareous deposits called kankar.
(4) Khadar: Composed of new alluvium. It is formed in the lower levels of the plains near the river. It is very fertile, as it is renewed almost every year, and is ideal for intensive agriculture.

Difference between Bhangar and Khadar

Importance of the Northern Plains
1. With fertile alluvial soils, a flat surface, slow-moving perennial rivers and a favourable climate, the Great Plains of North India are of great economic and social significance.
2. The fertile soil and assured water resources have made these plains rich agricultural land. They are the granaries of India.
3. The plains have a good network of roads and railways, which has led to large-scale industrialisation of the region.
4. As the region has sufficient employment opportunities, the density of population is high.
5. The Northern Plains are the site where the ancient civilisations of Mohenjo-daro and Harappa developed.

THE PENINSULAR PLATEAU

To the south of the Ganga plain lies the extensive Peninsular Plateau. This plateau covers nearly half of the area of India and is triangular in shape, with a broad base in the north and a narrow apex in the south. It is made up of ancient igneous and metamorphic rocks and is the oldest part of the Indian subcontinent. It was formed by the breaking and drifting of the Gondwana land and is therefore a part of the oldest landmass. The plateau has broad, shallow valleys and rounded hills. One of its distinct features is the black soil area known as the Deccan Trap. The Deccan Trap is of volcanic origin, so its rocks are igneous. These rocks have been denuded over time and are responsible for the formation of the black soil.

The Aravali Hills lie on the western and northwestern margins of the plateau. They are highly eroded hills found as broken hills and extend from Gujarat to Delhi in a southwest-northeast direction. The plateau has an undulating surface with gentle slopes. It is divided into two parts by the Narmada river:
(A) The Central Highlands
(B) The Deccan Plateau
The boundary between these two units is formed by the Vindhya Range.

The Central Highlands: The part of the Peninsular Plateau lying to the north of the Narmada, covering a major area of the Malwa Plateau, is known as the Central Highlands. The Vindhya range bounds the Central Highlands on the south and the Aravallis on the northwest. Its further westward extension gradually merges with the sandy and rocky desert of Rajasthan. The rivers draining this region, namely the Chambal, Sind, Betwa and Ken, flow from southwest to northeast, indicating the slope. The Central Highlands are wider in the west and narrower in the east. The eastward extensions of this plateau are locally known as Bundelkhand and Baghelkhand. The Chotanagpur Plateau marks the further eastward extension, drained by the Damodar river.

The highest peak of the peninsular region, Anai Mudi (2695 metres above sea level), is situated in Kerala. It is the highest peak of the Annamalai hills.

The Deccan Plateau: The eastern edge of the Deccan Plateau is marked by the Eastern Ghats. Unlike the Himalayas, which have sharp, lofty peaks, the hills of the peninsular region are low and do not have high peaks. Many rivers flow through the Deccan Plateau. The Narmada flows through a narrow rift valley between the Vindhyas to the north and the Satpuras to the south, and separates the Deccan Plateau from the Malwa Plateau. To the south of the Satpura range flows the Tapi. Like the Narmada, the Tapi flows into the Arabian Sea. Neither the Narmada nor the Tapi forms a delta. The other major rivers of the Deccan Plateau, including the Mahanadi, Godavari, Krishna and Kaveri, flow into the Bay of Bengal, and they form their deltas near the coast. The Godavari is the longest among the rivers of the Deccan Plateau.

Another distinct feature of the Peninsular Plateau is the Deccan Trap, formed by the continuous outpouring of lava from the interior of the earth.

The Northeastern Plateau: The Northeastern Plateau is an extension of the Deccan Plateau in the northeast, locally known as the Meghalaya and Karbi-Anglong Plateau. It is separated by a fault from the Chotanagpur Plateau. Three prominent hill ranges run from west to east: the Garo, the Khasi and the Jaintia Hills.

THE COASTAL PLAINS OF INDIA

The western and eastern coastal plains stretch along the western and eastern margins of the Deccan Plateau.

1. The Western Coast consists of three sections:
(A) Konkan
(B) Kanara
(C) Malabar
The northern part of the western coastal plain, in Maharashtra and Karnataka, is called the Konkan Coast. The southern part of this plain is called the Malabar Coast. A large number of backwaters called lagoons are found along the Kerala coast. Only a few large rivers, such as the Narmada, Tapi and Mahi, flow through the western coastal plain.

2. The Eastern Coast is wide and level. In its northern part it is referred to as the Northern Circars, while the southern part is known as the Coromandel Coast. Large rivers such as the Mahanadi, Godavari, Krishna and Kaveri have formed extensive deltas on this coast. Chilika Lake is an important feature along the eastern coast.

THE GREAT INDIAN DESERT

1. It lies to the west of the Aravali Range.
2. It occupies a major part of the state of Rajasthan and extends up to Sindh in Pakistan as the Thar Desert.
3. The land is generally sandy and covered with sand soil.
4. The region is dry, with hardly any rivers.
5. The Luni is the only river in this region.

THE ISLAND GROUPS

1. The Lakshadweep and the Andaman and Nicobar Islands are the main island groups of India.
2. Lakshadweep is located about 300 km west of the coast of Kerala in the Arabian Sea.
3. The Lakshadweep Islands are a group of 36 islands.
4. The Lakshadweep Islands were formerly known as Laccadive, Minicoy and Amindivi Islands. They were renamed Lakshadweep in 1973.
5. Lakshadweep is the smallest Union Territory in terms of area.
6. Kavaratti Island is the headquarters of Lakshadweep.
7. The Andaman and Nicobar Islands are located in the Bay of Bengal.
8. The southernmost point of India, called Indira Point, is located in Great Nicobar Island.
9. The Andaman and Nicobar Islands have as many as 200 islands.
10. The Nicobar group consists of 19 islands. These islands are fairly large and more numerous than the Lakshadweep islands.
11. Pitti Island, which is uninhabited, has a bird sanctuary in the Lakshadweep Islands.
12. These islands are known for their great diversity of flora and fauna.

INDIA AS A GEOGRAPHICAL UNIT

1. The northern mountains are the major sources of water and forest wealth.
2. The northern plains are the granaries of the country. They provide the base for early civilisations.
3. The plateau is a storehouse of minerals, which has played a crucial role in the industrialisation of the country.
4. The coastal regions and island groups provide sites for fishing and port activities.
5. Thus, the diverse physical features of the land have immense future possibilities of development.

GLOSSARY

1. Tarai Zone: A zone next to the Bhabar, which is wet and marshy. It has thick forest cover and a variety of wildlife.
2. Water divide: The upland that separates the flow of two rivers or river systems.
3. Delta: A triangular deposit of sediment at the mouth of a river. The river slows down at its mouth where it meets the sea, so mud and silt settle and form the delta.
4. Estuary: A narrow, deep valley at the mouth of a river where currents or tides are strong, or where the river's own current is swift.
5. Tributary: A river that joins the main river and increases its volume of water.
6. Plate tectonics: The scientific concept that explains the movements of the different plates of the earth's crust.
7. Gondwana land: A major portion of the crust that once included Australia, Peninsular India, South Africa and South America.
8. Tethys Sea: A narrow sea with a sinking bottom, lying between Gondwana land in the south and Angara land in the north.
9. Flood plain: A plain formed by sediment deposited by rivers year after year.
10. Bar: A deposit of sand or mud in the river channel.
11. Levees: An elevated bank flanking the channel of a river and standing above the level of the flood plain.
12. Lagoon: A salt water lake separated from the sea by sandbars.
13. Glacier: A slow-moving river of snow and ice.
14. Pass: A gap in a mountain range providing a natural route across it.
15. Alluvial plains: Flat, low-lying lands made of alluvium.
16. Diverging plates: Plates that are moving away from each other.
17. Converging plates: Plates that are coming together.
18. Perennial rivers: Rivers that flow throughout the year.
19. Fold mountains: Mountains formed during the most recent major phase of folding in the earth's crust.
20. Coral polyps: Short-lived, microscopic organisms that live in colonies.
21. Distributary: A river that branches off from a main river. It is formed near the river's mouth before it falls into the sea.
22. Gorge: A steep-sided, narrow and deep valley of a river formed in its upper course, also called a canyon. It is also called an I-shaped valley. For example, the Brahmaputra gorge (5500 m) and the Indus gorge.
23. Rift valley: A valley formed by the subsidence (sinking) of land between two blocks due to faulting.
24. Sand dune: A mound, ridge or low hill of loose, wind-blown sand.

EXERCISE

A. VERY SHORT ANSWER TYPE QUESTIONS

Q.1 Why are Shivaliks prone to landslides?
Q.2 What are the dunes and where are they found?
Q.3 What are tectonic plates?
Q.4 Explain plains are more fertile. Give two reasons.
Q.5 Which continents of today were a part of Gondwana land?
Q.6 Mention the three types of plates movements.
Q.7 Name the oldest landmass of the Indian subcontinent.
Q.8 What was the Gondwana land?
Q.9 Name the major rivers of the northern India.
Q.10 What is meant by doab?
Q.11 How is the northern plain divided on the basis of the differences in relief?
Q.12 What is Tarai Zone?
Q.13 What is barchan?
Q.14 Name any two peaks of the Western Ghat?
Q.15 Name two famous valleys in the state of Himachal Pradesh.
Q.16 Name two rivers which form estuaries?
Q.17 What are the dunes made up of? Give an example.
Q.18 What is a water divide?
Q.19 Name two passes of Eastern Himalayas?
Q.20 Name the seven major tectonic plates.
Q.21 How is the northern plain divided on the basis of the difference in the relief?
Q.22 What is the local name of the Western Ghats in:
(i) Maharashtra and Karnataka.
(ii) Along Kerala-Tamil Nadu Border
(iii) Tamil Nadu.
Q.23 Which is the highest peak of the Deccan plateau?
Q.24 Why are the Northern Plains primarily an agricultural belt?
Q.25 What is a distributary?
Q.26 Where do corals flourish?
Q.27 What are the three kinds of corals?
Q.28 Give an example of the barrier reef kind of coral reefs.
Q.29 What is the shape of the atolls?
Q.30 Distinguish between
(i) Converging and diverging tectonic plates.
(ii) Khadar and Bhangar
(iii) Western Ghats and Eastern Ghats.

B. SHORT ANSWER TYPE QUESTIONS

Q.1 "The land of India is characterised by a great diversity in its relief or physical features". Justify the statement.
Q.2 Write four points to explain the extent, length, width and height of the Himalayas.
Q.3 How are the Himalayas divided in the east-west direction?
Q.4 What is the 'bhabar'? Explain.
Q.5 Write any four major characteristics of the northern plains of India.
Q.6 Write any four characteristics of Ganga-Bhamputra delta.
Q.7 Mention some features of the Ganga Basin.
Q.8 Explain how the Himalayas act as a boon for India.
Q.9 Distinguish between delta and an estuary.
Q.10 Mention any four features of the Peninsular plateau.
Q.11 What is Purvanchal?
Q.12 Write brief facts about Lakshadweep Island.
Q.13 Write any three features of Karakoram mountains range.
Q.14 Differentiate between western Himalayas and eastern Himalayas.
Q.15 Give a brief description of the Indian Desert.
Q.16 What is the difference between a gorge and a rift valley?
Q.17 What is the difference between a tributary and a distributary?
Q.18 How are coral reefs formed? Name two examples of coral reefs.

C. LONG ANSWER TYPE QUESTIONS

Q.1 Name the major divisions of the Himalayas from north to south.
Q.2 Give an account of the northern Plains.
Q.3 Give an account of the Island groups of India.
Q.4 Contrast the relief of the Himalayan region with that of the Peninsular Plateau.
Q.5 Name the four physical divisions of India and explain any one.
Q.6 Give a brief account of the great plains of North India.
Q.7 What are the uses of the Himalayas? Explain.
Q.8 Compare the main features of the western coastal plain and eastern coastal plain.
Q.9 Describe how the Himalayas were formed.

D. MULTIPLE CHOICE QUESTIONS

Q.1 Guru Shikhar is the highest peak of the -
(A) Aravallis (B) Vindhyas (C) Satpuras (D) Western Himalayas

Q.2 A narrow opening in a mountain range which provides passage through the mountain is -
(A) Strait (B) Valley (C) Pass (D) None of these

Q.3 Shipkila, Bhor, Nathula and Pal are -
(A) Peaks (B) Passes (C) Ranges (D) All the above

Q.4 K2 is the highest peak of the -
(A) The Karakoram (B) Vindhyan (C) Satpura (D) Western Himalayas

Q.5 Name the second highest mountain peak of the world?
(A) K2 (B) Guru Shikhar (C) Mt. Everest (D) None of these

Q.6 Where is Mt. Everest situated?
(A) India (B) Nepal (C) China (D) Pakistan

Q.7 Where does the Ganga enter the northern plains?
(A) Delhi (B) Mumbai (C) Haridwar (D) Allahabad

Q.8 What is the other name of the west coast -
(A) Malabar coast (B) Coromandel coast (C) Nilgiri (D) All the above

Q.9 Which plateau lies between the Aravali and the Vindhya range -
(A) Deccan (B) Central (C) Malwa (D) Peninsular

Q.10 Which river flows north west between Zaskar and Ladakh ranges?
(A) Indus (B) Ganga (C) Yamuna (D) Narmada

Q.11 Where are Lakshadweep Islands situated -
(A) Arabian sea (B) Bay of Bengal (C) Pacific ocean (D) Indian ocean

Q.12 What is the average height of the Greater Himalayas -
(A) 8000 m (B) 7000 m (C) 6000 m (D) 2000 m

Q.13 Where do frequent landslides occur in the Himalayas during winter and rainy season?
(A) Shivalik (B) Himadri (C) Middle Himalaya (D) None of these

Q.14 Which river marks the eastern-most boundary of the Himalayas?
(A) Ganga (B) Brahmaputra (C) Yamuna (D) Godavari

Q.15 Which soil dominates the Peninsular Plateau?
(A) Red soil (B) Alluvial soil (C) Black soil (D) Laterite soil

Q.16 ......... is the main river of the Indian desert -
(A) Ganga (B) Indus (C) Krishna (D) Luni

ANSWER KEY

Q.1 A, Q.2 C, Q.3 B, Q.4 A, Q.5 A, Q.6 B, Q.7 C, Q.8 A, Q.9 C, Q.10 A, Q.11 A, Q.12 C, Q.13 A, Q.14 B, Q.15 A, Q.16 D

Note: the printed key gives B for Q.8, which is the Coromandel coast (the eastern coast). The other name of the west coast is the Malabar coast, so the correct answer is A.

(C)Transform Plates : Converging plates sometime neither collide with each nor slide under the other but they move horizontally push each other. Such plates are called the transform plates and boundary they make is called the transform boundary.

Formation of Himalayas :