Physical Features of India Class 9 Notes Social-Science Geography Chapter 2

Points to Remember

1. Introduction

(i) India is a vast country with varied landforms i.e.,mountains, plains, deserts, plateaus and islands.

(ii) India is a large landmass formed during differentgeological periods which has influenced her relief.

2. Theory of Tectonic Plates

(i) According to the ‘‘Theory of Plate Tectonics’’ the crust(upper part) of the Earth has been formed out of seven major and some minor plates.

(ii) The movement of the plates resulted in the building up of stresses within the plates leading to folding, faulting and volcanic activity.

(iii) Plate movements are classified into 3 types. i.e.,

  • (a) Some plates come towards each other and form convergent boundary.
  • (b) Some plates move away from each other and form divergent boundary.
  • (c) At times, they may also move horizontally past each other and form a transform boundary.

(iv) The movements of these plates have changed the position and size of the continents over millions of years.

(v) Such movements have also influenced the evolution of the present landform features of India.

(vi) The oldest landmass (the Peninsular part) was a part of Gondwana land in ancient times.

(vii) Gondwana land included India, Australiar, South Africa and South America as one single landmass.

(viii) Convectional currents split the crust of the Earth into of pieces, thus leading to the drifting of the Indo-Australian plate towards North after being separated from Gondwana land.

(ix) The northward drift resulted in the collision of the plate with the much larger Eurasian plate.

(x) Due to the collision, the sedimentary rocks which wereaccumulated in the geocyncline, got folded the form of themountain systems of Western Asia and the Himalayas.

3. The Northern Plains

(i) The Himalayan uplift of the Tethys sea and the subsidence of the northern flank of the peninsular plateau resulted in the formation of a large basin.

(ii) Gradually, the basin got filled with deposition of sediment by the rivers flowing from the mountains in thenorth and the peninsular plateau in the south.

(iii) A flat land of extensive alluvial deposits led to the formation of the northern plains.

4. Major Physiographic Divisions

(i) The Himalayan Mountains

(ii) The Northern Plains

(iii) The Peninsular Plateau

(iv) The Indian Desert

(v) The Coastal Plains

(vi) The Islands

(vii) The Himalayas are geologically young and structurally fold mountains. They stretch across the northern borders of India.

(viii) They are the longest range in India, covering an arc of about 2,400 km.

(ix) These mountain ranges run in a West-East direction from the Indus to the Brahmaputra.

(x) The Himalayas consist of three parallel ranges in longitudinal extent.

(xi) The northernmost range is known as the Great or InnerHimalayas or the ‘Himadri’. It is a continous range withan average height of 6,000 metres. It contains all theprominent Himalayan peaks.

(xii) The core of this part of Himalayas is composed of granite.

(xiii) Himachal or lesser Himalayas lie to the South of the Himadri.

(xiv) The altitude in the lesser Himalayas varies between 3,700 and 4,500 metres and the average width is 50 km.

(xv) The Pir Panjal range forms the longest and the most important range in these Hills. The Dhaula Dhar and the Mahabharat ranges are also prominent here.

(xvi) This range consists of the famous Valley of Kashmir, Kangra and Kullu Valley in Himachal Pradesh.

5. Shiwaliks The outermost range of the Himalayas is calledShiwaliks.

(i) They extend over a width of 10-50 km and have an altitude varying between 900 and 1100 metres.

(ii) The longitudinal valleys lying between the lesser Himalayas and the Shiwaliks are known as Duns. DehraDun, Kotli Dun, etc.

(iii) This range is composed of unconsolidated sediments brought down by the rivers.

(iv) The Himalayas have also been divided on the basis of regions from West to East. These regions have been demarcated by river valleys. e.g.,

(v) Punjab Himalayas – lie between Indus and Satluj rivers.

(vi) Kumaon Himalayas – lie between Satluj and Kali rivers.

(vii) Nepal Himalayas – lie between Kali and Tista rivers.

(viii) Assam Himalayas – lie between Tista and Dihang rivers.

(ix) There are some regional names also of the Himalayas.

(x) Beyond the Dihang gorge the Himalayas bend sharply to the South and spread along the eastern boundary of India. They are known as Purvachal or the Eastern hills and mountains.

(xi) These hills running through the northeastern states are mostly composed of sedimentary rocks covered with dense forests.

(xii) The Purvachal comprises of the Patkai hills Naga hills, Manipur hills and Mizo hills.

6. The Northern Plain

(i) The Northern plains has been formed by the interplay of 3 major river systems namely the Indus, the Ganga and the Brahmaputra along with their tributaries.

(ii) This plain is formed of alluvial soil deposited in a vast basin over millions of years.

(iii) It spreads in an area of 7 lakh sq km.

(iv) The plain is 2400 km long and 240-320 km broad.

(v) It is densely populated with rich soil, adequate water supply and favourable climate. It is agriculturally a very productive part of India.

(iv) The Northern plain is broadly divided into 3 sections. These are the Punjab plains, Ganga plains and Brahmaputra plains.

7. The Punjab Plains

(i) The Western part of the Northern plains is referred to as the Punjab plains.

(ii) Formed by the Indus and its tributaries, a large part of this plain lies in Pakistan.

(iii) 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.

8. The Ganga Plains

(i) The Ganga plains extends between the Ghaggar and Teesta rivers.

(ii) It is spread over the states of Haryana, Delhi, UP, Bihar, partly Jharkhand and the West Bengal.

9. The Brahmaputra Plains

(i) To the east of the Ganga plains lies the Brahmaputra plains

(ii) This lies mostly in Asom

10. Division of the Northern Plains on the Basis of Relief

Features The Northern plains also have diverse relief features. These are

(a) Bhabar

The rivers, after coming down from the mountains, deposit pebbles in a narrow area which is lying parallel to the slopes of the Shiwaliks. It is known as Bhabar. All the streams disappear in the Bhabar belt.

(b) The Terai Belt

  • The streams and the rivers re-emerge and create a wet swampy and marshy region known as the Terai.
  • The Terai region is a thickly forested region full of wildlife.

(c) Bhangar

  • The largest part of the Northern plains is formed of older alluvium. The Bhangar lies above the flood plains of the rivers and present a terrace like feature.
  • This soil contains calcareous deposits locally known as Kankar.

(d) Khadar

  • The newer and younger deposits of the flood plains are called Khadar.
  • They are renewed almost every year so they are fertile and thus ideal for intensive agriculture.

11. The Peninsular Plateau

(i) The Peninsular plateau is a table land composed of old crystalline igneous and metamorphic rocks.

(ii) It was formed due to the breaking and drifting of Gondwana land thus making it a part of the oldest landmass.

(iii) This plateau consists of two broad divisions, namely the central highlands and the Deccan plateau.

12. The Central Highlands

(i) 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.

(ii) The Vindhyan range bounds the central highlands on the South and the Aravalis on the North-West.

(iii) The flow of the rivers draining this region, namely the Chambal, Sind, Ken and Betwa is from South-West to North East.

(iv) The central highlands are wider in the West but narrower in the East.

(v) The eastward extensions of this plateau are locally known as Bundelkhand and Baghelkhand.

(vi) The Chhotanagpur plateau marks the further eastward extension, and is drained by the Damodar river.

(vii) The Deccan plateau is a triangular landmass that lies to the south of the Narmada river.

(viii) The Satpura range flanks its broad base in the North while the Mahadev, the Kaimur and Maikal range form its Eastern extensions.

(ix) An extension of the plateau is also visible in theNorth-East locally known as Meghalaya Karbi-Anglongplateau and North Cachar hills.

(x) Three prominent hill ranges in Meghalaya from the west to east are the Garo, the Khasi and the Jaintia hills.

13. The Western Ghats

(i) The Western Ghats lie parallel to the Western coast.

(ii) They are continuous and can only be crossed through passes .

(iii) The Western Ghats are higher than the Eastern Ghats.

(iv) Their average elevation is 900-1600 metres as against 600 metres of the Eastern Ghats.

(v) The height of the Western Ghats progressively increases from North to south.

(vi) The highest peaks include the Annai Mudi (2,695 metres and the Doda Betta (2,637 metres). The Western Ghats cause orographic rain by facing the rain bearing moist winds.

14. The Eastern Ghats

(i) The Eastern Ghats stretch from the Mahanadi Valley to the Nilgiris in the South.

(ii) The Eastern Ghats are discontinuous, irregular and dissected by rivers draining into the Bay of Bengal.

(iii) Mahendragiri (1501 metres) is the highest peak in the Eastern Ghats.

(iv) They have the hill stations of Udagamandalam (popularly known as Ooty) and Kodaikanal, both in Tamil Nadu.

(v) The Eastern Ghats mark the Eastern edge of the Deccan plateau.

(vi) The average height of the Eastern Ghats is 600 metres.

15. The Indian Desert

(i) The Indian desert lies towards the eastern margins of the Aravali hills.

(ii) It is an undulating sandy plain covered with sand dunes

(iii) This region receives very low rainfall, below 150 mm per year.

(iv) It has arid climate with low vegetation cover.

(v) Streams appear during the rainy season.

(vi) Soon after, they disappear into the sand as they do not have enough water to reach the sea.

(vii) Luni is the only large river in this region.

(viii) Barchans (crescent shaped dunes) cover large areas but longitudinal dunes become more prominent near the India-Pakistan border.

16. The Coastal Plains

(i) The Peninsular plateau is flanked by stretches of narrow coastal strips, running along the Arabian Sea on the west and the Bay of Bengal on the east.

(ii) The western coast sandwiched between the Western Ghats and the Arabian Sea is a narrow plain. It consists of three sectors.

(iii) The northern part of the coast is called Konkan (Mumbai -Goa). The central stretch is called the Kannad plain while the southern stretch is referred to as the Malabar coast.

(iv) 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.

(v) Large rivers such as the Mahanadi, Godavari, Krishna and Kaveri have formed extensive deltas on this coast.

(vi) Lake Chilka is an important feature along the Eastern coast.

17. The Islands

(i) India has two groups of islands.

(ii) The Lakshadweep Islands group is lying close to the Malabar coast of Kerala.

(iii) This group of islands is composed of small coral islands.

(iv) Earlier they were known as Laccadive, Minicoy and Anainative. In 1973, they were named as Lakshadweep.

(v) They coverts a small area of 32 sq km.

(vi) Kavaratti Island is the administrative headquarters of Lakshadweep.

(vii) This island group has great diversity of flora and fauna. Pitti island, which is uninhabited, has a bird sanctuary.

18. Andaman and Nicobar Islands

(i) The elongated chain of islands located in the Bay of Bengal extending from north to south are the Andaman and Nicobar Islands.

(ii) They are bigger in size and more numerous and scattered, compared to Lakshadweep.

(iii) The entire group of islands is divided into two broad categories. The Andaman in the North and Nicobar in the South.

(iv) It is believed that these islands are an elevated portion of submarine mountains.

(v) These islands are of great strategic importance for the country.

(vi) There is great diversity of flore and fauna on this island group.

(vii) The islands lie close to the equator and experience a equatorial climate and have thick forest cover.

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