Class 9 Social Science Notes Chapter 2 (Physical Features of India) – Contemporary India Book

Alright class, let's focus on Chapter 2, 'Physical Features of India'. This is a crucial chapter not just for your exams but also for understanding the geographical diversity of our country, which influences everything from climate and vegetation to economy and culture. We'll break down the formation and characteristics of India's varied landforms.

Understanding the Formation: The Theory of Plate Tectonics

Before we look at the specific features, remember the underlying reason for this diversity: Plate Tectonics.

• The Earth's crust (the lithosphere) is broken into several large and small rigid pieces called tectonic plates.
• These plates are constantly moving very slowly over the semi-molten layer below (asthenosphere).
• Plate movements are categorized into three types:
  • Convergent Boundary: Plates move towards each other. This can cause collision (leading to mountain formation like the Himalayas) or one plate sliding under another (subduction).
  • Divergent Boundary: Plates move away from each other, creating gaps where molten material rises, forming new crust (like mid-ocean ridges).
  • Transform Boundary: Plates slide horizontally past each other.
• India's landmass (part of the Indo-Australian plate) drifted northwards after breaking away from the ancient supercontinent Gondwana Land (which included South America, Africa, Antarctica, Australia, and India).
• This northward drift led to the collision of the Indian plate with the much larger Eurasian plate.
• The collision caused the sedimentary rocks accumulated in the Tethys Sea (the geosyncline between the plates) to fold and uplift, forming the Himalayan mountain system. This process is still ongoing, making the Himalayas geologically young and prone to earthquakes.
• The uplift of the Himalayas and the subsidence of the northern flank of the Peninsular Plateau created a large basin, which was gradually filled with sediments deposited by rivers flowing from the Himalayas (north) and the Peninsular Plateau (south), forming the fertile Northern Plains.

Major Physiographic Divisions of India

India's physical features can be broadly grouped into the following six divisions:

1. The Himalayan Mountains

• Location & Extent: Stretch over the northern borders of India, running west-east from the Indus River to the Brahmaputra River. They form an arc covering about 2,400 km. Their width varies from 400 km in Kashmir to 150 km in Arunachal Pradesh.
• Nature: Geologically young and structurally fold mountains. Represent the loftiest and one of the most rugged mountain barriers in the world.
• Parallel Ranges (Longitudinal): Consist of three main parallel ranges:
  • The Great or Inner Himalayas (Himadri):
    • Northernmost range.
    • Most continuous range, average height of 6,000 metres.
    • Contains the highest peaks: Mt. Everest (Nepal), Kanchenjunga (India), Makalu, Dhaulagiri, Nanga Parbat, Annapurna, Nanda Devi, Kamet, Namcha Barwa.
    • The core is composed of granite.
    • Perennially snow-bound; numerous glaciers originate here.
  • The Lesser Himalayas (Himachal):
    • Lies south of the Himadri.
    • Altitude varies between 3,700 and 4,500 metres; average width is 50 km.
    • Mainly composed of highly compressed and altered rocks.
    • Ranges include Pir Panjal (longest), Dhaula Dhar, and Mahabharat ranges.
    • Famous for valleys like Kashmir, Kangra, and Kullu. Well-known for hill stations (Shimla, Mussoorie, Nainital).
  • The Outer Himalayas (Shiwaliks):
    • Outermost range.
    • Width extends over 10-50 km; altitude varies between 900 and 1,100 metres.
    • Composed of unconsolidated sediments brought down by rivers from the main Himalayan ranges.
    • Valleys are covered with thick gravel and alluvium.
    • Longitudinal valleys lying between the Lesser Himalayas and the Shiwaliks are known as Duns (e.g., Dehra Dun, Kotli Dun, Patli Dun).
• West-to-East Divisions (Demarcated by River Valleys):
  • Punjab Himalayas: Between Indus and Satluj rivers (also known regionally as Kashmir and Himachal Himalaya).
  • Kumaon Himalayas: Between Satluj and Kali rivers.
  • Nepal Himalayas: Between Kali and Tista rivers.
  • Assam Himalayas: Between Tista and Dihang rivers (Brahmaputra).
• The Purvachal or Eastern Hills:
  • Beyond the Dihang gorge, the Himalayas bend sharply south, spreading along India's eastern boundary.
  • Composed mainly of strong sandstones (sedimentary rocks).
  • Covered with dense forests, mostly run as parallel ranges and valleys.
  • Includes the Patkai hills, Naga hills, Manipur hills, and Mizo hills.

2. The Northern Plain

• Formation: Formed by the depositional work of three major river systems – the Indus, the Ganga, and the Brahmaputra, along with their tributaries. Composed of alluvial soil deposited over millions of years.
• Extent: Spreads over an area of 7 lakh sq. km. About 2,400 km long and 240 to 320 km broad.
• Significance: Densely populated due to rich soil cover, adequate water supply, and favourable climate. Agriculturally very productive.
• Divisions:
  • Punjab Plains: Western part, formed by the Indus and its tributaries (Jhelum, Chenab, Ravi, Beas, Satluj). Large part lies in Pakistan. Dominated by 'doabs' (land between two rivers).
  • Ganga Plain: Extends between the Ghaggar and Teesta rivers. Spreads over Haryana, Delhi, UP, Bihar, parts of Jharkhand, and West Bengal.
  • Brahmaputra Plain: Lies mainly in Assam.
• Relief Feature Divisions (Based on variation in relief, from North to South):
  • Bhabar: Narrow belt (8-16 km wide) parallel to the Shiwalik foothills. Rivers deposit pebbles here. Streams often disappear in this zone. Not suitable for agriculture.
  • Terai: South of Bhabar. Streams and rivers re-emerge here, creating a wet, swampy, and marshy region. Was thickly forested, rich in wildlife; much has been cleared for agriculture. Dudhwa National Park is in this region.
  • Bhangar: Largest part of the Northern Plain, formed of older alluvium. Lies above the floodplains, presents a terrace-like feature. Soil contains calcareous deposits locally known as 'kankar'. Less fertile than Khadar.
  • Khadar: Newer, younger deposits of the floodplains. Renewed almost every year, so very fertile. Ideal for intensive agriculture.

3. The Peninsular Plateau

• Nature: A tableland composed of old crystalline, igneous, and metamorphic rocks. It's the oldest landmass, formed due to the breaking and drifting of the Gondwana land.
• Features: Characterized by broad and shallow valleys and rounded hills.
• Major Divisions:
  • The Central Highlands:
    • Part lying north of the Narmada river, covering a major area of the Malwa plateau.
    • Bounded by the Vindhya range (south), Satpura range (south of Narmada), and Aravallis (northwest).
    • Rivers draining this region (Chambal, Sind, Betwa, Ken) flow from southwest to northeast, indicating the slope.
    • Wider in the west, narrower in the east.
    • Eastward extensions are locally known as Bundelkhand and Baghelkhand. The Chotanagpur plateau marks the further eastward extension, drained by the Damodar river.
  • The Deccan Plateau:
    • Triangular landmass south of the Narmada river.
    • Bounded by the Satpura range (north), Mahadev hills, Kaimur hills, and Maikal range (east).
    • Higher in the west and slopes gently eastwards.
    • An extension is visible in the northeast, known as the Meghalaya, Karbi-Anglong Plateau, and North Cachar Hills (separated by a fault from the Chotanagpur Plateau). Three prominent hill ranges here are the Garo, Khasi, and Jaintia Hills.
• Western and Eastern Ghats: These mark the western and eastern edges of the Deccan Plateau respectively.
  • Western Ghats:
    • Run parallel to the western coast. Continuous, can be crossed only through passes (Thal, Bhor, Pal Ghats).
    • Higher than Eastern Ghats (average elevation 900–1600 m).
    • Cause orographic rain by blocking rain-bearing monsoon winds.
    • Height increases from north to south. Highest peaks include Anai Mudi (2,695 m) in the Anaimalai Hills and Doda Betta (2,637 m) in the Nilgiri Hills.
  • Eastern Ghats:
    • Stretch from the Mahanadi Valley to the Nilgiris in the south.
    • Discontinuous and irregular, dissected by rivers draining into the Bay of Bengal (Mahanadi, Godavari, Krishna, Kaveri).
    • Average elevation is about 600 m.
    • Highest peak is Mahendragiri (1,501 m). Shevaroy Hills and Javadi Hills are located to the southeast.
    • The Nilgiris mark the junction where Western and Eastern Ghats meet. Famous hill station Udagamandalam (Ooty) is located here.
• Deccan Trap: A distinct feature of the Peninsular plateau is the black soil area. Of volcanic origin, hence rocks are igneous. These rocks have denuded over time and are responsible for the formation of black soil (Regur soil), ideal for cotton cultivation.
• Aravalli Hills: Lie on the western and northwestern margins. Highly eroded hills, found as broken hills. Extend from Gujarat to Delhi in a southwest-northeast direction.

4. The Indian Desert

• Location: Lies towards the western margins of the Aravalli Hills.
• Features: An undulating sandy plain covered with sand dunes.
• Climate: Arid region receiving very low rainfall (below 150 mm per year). Has arid climate with low vegetation cover.
• Hydrology: Streams appear only during the rainy season and disappear quickly into the sand as they lack enough water to reach the sea. Luni is the only large river in this region.
• Sand Dunes: Barchans (crescent-shaped dunes) cover larger areas, but longitudinal dunes become more prominent near the Indo-Pakistan boundary.

5. The Coastal Plains

• Location: Flanking the Peninsular Plateau are narrow coastal strips.
• Western Coastal Plain:
  • Sandwiched between the Western Ghats and the Arabian Sea. It's a narrow plain.
  • Consists of three sections:
    • Konkan: Northern part (Mumbai – Goa).
    • Kannad Plain: Central stretch.
    • Malabar Coast: Southern stretch.
• Eastern Coastal Plain:
  • Lies along the Bay of Bengal. It is wide and level.
  • Divided into two parts:
    • Northern Circar: Northern part.
    • Coromandel Coast: Southern part.
  • Large rivers like the Mahanadi, Godavari, Krishna, and Kaveri have formed extensive deltas on this coast.
  • Lake Chilika (Odisha), the largest salt water lake in India, lies to the south of the Mahanadi delta.

6. The Islands

India has two main groups of islands:

• Lakshadweep Islands:
  • Located close to the Malabar coast of Kerala in the Arabian Sea.
  • Composed of small coral islands. (Corals are skeletons of tiny marine animals called Polyps).
  • Earlier known as Laccadive, Minicoy, and Amindive. Named Lakshadweep in 1973.
  • Covers a small area of 32 sq km.
  • Kavaratti island is the administrative headquarters.
  • Pitti island, which is uninhabited, has a bird sanctuary.
  • Rich in biodiversity.
• Andaman and Nicobar Islands:
  • Located in the Bay of Bengal, extending from north to south.
  • They are bigger in size, more numerous, and scattered.
  • Divided into two broad groups: The Andaman in the north and The Nicobar in the south.
  • Believed to be an elevated portion of submarine mountains.
  • Strategically important. Great diversity of flora and fauna.
  • Lie close to the equator, experience equatorial climate, and have thick forest cover.
  • Port Blair is the capital city.
  • India's only active volcano is found on Barren island in this group.

Conclusion: Interdependence of Physical Divisions

These diverse physical features are complementary. The mountains are major sources of water and forest wealth. The northern plains are the granaries of the country. The plateau is a storehouse of minerals, crucial for industrialization. The coastal regions and island groups provide sites for fishing and port activities. This vast physical diversity makes India rich in natural resources and influences the life of its people profoundly.

Multiple Choice Questions (MCQs)

1. The northernmost range of the Himalayas is known as:
   a) Himachal
   b) Shiwalik
   c) Himadri
   d) Purvachal

2. Which plateau lies between the Aravalli and the Vindhya ranges?
   a) Chotanagpur Plateau
   b) Malwa Plateau
   c) Deccan Plateau
   d) Karbi-Anglong Plateau

3. The longitudinal valleys lying between the Lesser Himalayas and the Shiwaliks are known as:
   a) Doabs
   b) Duns
   c) Terai
   d) Bhabar

4. Which is the highest peak in the Eastern Ghats?
   a) Anai Mudi
   b) Kanchenjunga
   c) Mahendragiri
   d) Doda Betta

5. The wet, swampy, and marshy region south of the Bhabar belt is known as:
   a) Khadar
   b) Bhangar
   c) Terai
   d) Doab

6. Lakshadweep Islands are composed of:
   a) Volcanic rocks
   b) Small coral islands
   c) Elevated submarine mountains
   d) Alluvial deposits

7. Which river forms the easternmost boundary of the Himalayas geographically?
   a) Indus
   b) Ganga
   c) Teesta
   d) Brahmaputra (Dihang)

8. The largest part of the Northern Plain, formed of older alluvium containing calcareous deposits ('kankar'), is called:
   a) Bhabar
   b) Terai
   c) Bhangar
   d) Khadar

9. India's only active volcano is located on which island?
   a) Kavaratti Island
   b) Pitti Island
   c) Barren Island
   d) Minicoy Island

10. The collision between which two tectonic plates led to the formation of the Himalayas?
    a) African and Eurasian Plates
    b) Indo-Australian and Pacific Plates
    c) North American and Eurasian Plates
    d) Indo-Australian and Eurasian Plates

Answer Key for MCQs:

1. c) Himadri
2. b) Malwa Plateau
3. b) Duns
4. c) Mahendragiri
5. c) Terai
6. b) Small coral islands
7. d) Brahmaputra (Dihang)
8. c) Bhangar
9. c) Barren Island
10. d) Indo-Australian and Eurasian Plates

Study these notes thoroughly. Understanding the spatial distribution and formation processes is key. Good luck with your preparation!