Class IX

Geography

Unit II – Physical Features of India

Notes

Marble is a very hard rock. It is used in the construction of the Taj Mahal.

Soap stone is a very soft rock. It is used in making talcum powder.

Soil colour varies from one place to another because soil is formed out of different types of rocks.

Geological formations, weathering, erosion and deposition are the major factors that are responsible for India’s relief features as they exist today.

“Theory of Plate Tectonics” explains how the physical features of earth were formed and modified.

The crust of the earth is made of seven major plates (and a few minor plates). The movement of the plates results in folding, faulting, earthquakes, volcanic eruptions etc. The plates may move towards each other or away from each other.

Earthquakes and volcanic eruptions occur mostly at plate margins.

Once upon a time, India, Australia, South Africa and South America existed together in as a single landmass. It was called the Gondwana Land. It was the southern part of the super continent called Pangea.

The northern part of Pangea was called Angara Land.

The Indo-Australian plate broke up from the Gondwana Land, drifted northwards and collided with the Eurasian plate. The collision caused the sedimentary rocks in the Tethys Sea to fold, resulting in the formation of the Himalayas and the mountain systems of western Asia.

The Peninsular Plateau in India is one of the oldest landmasses on the earth’s surface. It was a part of the Gondwana Land. Later, the Himalayas were formed. The Great Plains in northern India were formed much later.

Major physiographic divisions of India

-         The Himalayas

-         The Northern Plains

-         The Peninsular Plateau

-         The Indian Desert

-         The Coastal Plains

-         The Islands

The Himalayas

-         Geologically young

-         Structurally fold mountains

-         Run in a west-east direction from the Indus to the Brahmaputra

-         The loftiest mountain system in the world

-         In the shape of an arc that is about 2,400 km long

-         The Brahmaputra marks the easternmost boundary

-         About 400 km wide in Kashmir

-         About 150 km wide in Arunachal Pradesh

-         The altitudinal variations are more in the eastern half than in the western half.

-         Consist of three parallel ranges namely the Himadri or the Greater Himalayas or the Inner Himalayas, the Himachal or the Lesser Himalayas and the Siwaliks or the Outer Himalayas

The Purvanchal or the Eastern hills

-         Himalayas in the north-eastern states are known as the Purvanchal hills or the Eastern hills

-         Mostly composed of strong sandstone, a sedimentary rock

-         Covered with dense forests

-         Comprise the Patkai hills, the Naga hills, Manipur hills and the Mizo hills

The Himadri or the Greater Himalayas or the Inner Himalayas

-         The most continuous range

-         Consists of the world’s highest and famous peaks

-         Average altitude 6,000 m

-         Kanchenjunga (8,598 m) is the highest peak in India and the third highest peak in the world. It is in Sikkim, along the border of India and Nepal. If Pakistan-occupied-Kashmir is also considered, the highest peak is K² or Godwin Austin (8,611 m). K2, in the Karakoram range, is the second highest peak after Mount Everest.

-         Nanga Parbat, Nanda Devi, Kamet and Namcha Barwa are the other important Himalayan peaks in India.

-         Everest, Makalu, Dhaulagiri, Annapurna and Gurla Mandhata are the important Himalayan peaks in Nepal.

-         Snow-bound throughout the year

-         A number of glaciers originate from the Himadri

-         The core of the Himadri is composed of granite rock.

The Himachal or the Lesser Himalayas

-         The most rugged mountain system in the world

-         Composed of highly compressed and altered rocks

-         Altitude between 3,700 m and 4,500 m

-         Average width 50 km

-         Comprises the Pir Panjal, the Dhaula Dhar and the Mahabharat ranges

-         The Pir Panjal is the longest and the most important range

-         Includes the Kangra valley and the Kulu valley in Himachal Pradesh and the Kashmir valley

-         Well known for hill stations like Mussoorie (Uttarakhand), Nainital (Uttarakhand), Ranikhet (Uttarakhand) etc.

The Siwaliks or the Outer Himalayas

-         The outermost range of the Himalayas

-         Width 10 – 50 km

-         Altitude 900 – 1100 m

-         Composed of unconsolidated sediments brought down by the rivers from the northern ranges

-         Covered with gravel and alluvium

-         Comprise duns like Dehra Dun, Patli Dun and Kotli Dun

Duns: Longitudinal valleys between the Lesser Himalayas and the Siwaliks

Punjab Himalayas / Kashmir Himalayas / Himachal Himalayas: They are between the Indus and the Satluj rivers.

Kumaon Himalayas: They are between the Satluj and the Kali rivers.

Nepal Himalayas: They are between the Kali and the Tista rivers.

Assam Himalayas: They are between the Tista and the Dihang (Brahmaputra) rivers.

The Great Plain or the Northern Plain or the Indo-Gangetic Plain

-         Granaries of the country, base for early civilizations

-         Comprises the Indus, the Ganga and the Brahmaputra and their tributaries

-         Formed of alluvial soil deposits for millions of years

-         About 2400 km long; 240 – 320 km broad; area 7 lakh km²

-         Densely populated

-         Agriculturally very productive because of fertile soil, abundant water availability and favourable climate

-         Divisions: the Punjab Plains, the Ganga Plain and the Brahmaputra Plain

The Punjab Plains

-         The western part of the Northern Plain

-         Formed by the Indus and its tributaries (the Ravi, the Beas, the Jhelum, the Satluj and the Chenab)

-         Mostly in Pakistan

-         Dominated by the doabs

The Ganga Plain

-         The central part of the Northern Plain

-         Between the Ghaggar and the Tista rivers

-         Spread over Haryana, Delhi, UP, Bihar, a part of Jharkhand and West Bengal

The Brahmaputra Plain

-         The easternmost part of the Northern Plain

-         Mostly in Assam

Riverine islands: These are formed in the lower course of the river because the slope is gentle and the velocity of the river decreases.

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

Distributaries: The channels into which a river splits in its lower course

Doab: Do + ab (two rivers)

Punjab: Panch + ab (five rivers)

It is incorrect to think that the Northern Plain is a flat land without any variations in relief.

Divisions of Northern Plain on the basis of relief features

-         Bhabar

-         Terai

-         Bhangar

-         Khadar

Bhabar

-         Located at the foot of the Siwaliks

-         A narrow belt (8 – 16 km wide)

-         Composed of deposits of pebbles and stones

-         Streams disappear in this region

Terai

-         Streams and rivers reemerge in this region

-         wet, swampy and marshy

-         thickly forested; full of wildlife

-         Dudhwa National Park, a tiger reserve in Uttar Pradesh, is located in the terai belt of the Northern Plain

Bhangar

-         Older alluvium

-         Occupies the largest part of the Northern Plain

-         Lie above the floodplains; terrace-like

-         Contains calcareous (calcium carbonate) deposits

Kankar: Local name of calcareous deposits in bhangar

Khadar

-         Newer, younger alluvium

-         Renewed every year

-         Very fertile

-         Ideal for intensive agriculture

The Peninsular Plateau

-         A tableland

-         Composed of old crystalline, igneous and metamorphic rocks

-         Storehouse of minerals; has a crucial role in the industrialization of India

-         Broad divisions: Central Highlands, Deccan Plateau

-         The Narmada river demarcates the two divisions

The Central Highlands

-         Central Highlands lie north of Narmada. This part is called Malwa Plateau.

-         Wider in the west, narrower in the east

-         The Vindhyas lie south of the Central Highlands and the Aravallis lie northwest of the Central Highlands.

-         The western part of the Malwa Plateau merges with the desert in Rajastan

-         The Malwa Plateau is drained by the Chambal, the Sind, the Betwa and the Ken rivers. They flow from southwest to northeast. (It gives you an idea of the direction of the slope.)

-         The eastern part of the Central Highlands consist of Bundelkhand and Bagelkhand

-         The Chota Nagpur Plateau, drained by the Damodar, is the easternmost part of the Central Highlands.

The Deccan Plateau

-         A triangular landmass

-         Lies south of the Narmada

-         The Satpura range is the northern boundary

-         Western Ghats mark the western edge

-         Eastern Ghats mark the eastern edge

-         The Mahadev hills, the Kaimur hills and the Maikala hills lie northeast of the Deccan Plateau; Also lying in the northeast are Meghalaya and Karbi-Anglong Plateau and Garo hills, Khasi hills and Jaintia hills

-         Slopes from west to east

-         Separated by a fault from the Chota Nagpur Plateau

-          The part of the Deccan Plateau containing black soil is known as the Deccan Trap, of volcanic origin.

The Aravallis

-         Highly eroded, broken hills

-         Run in a southwest – northeast direction

-         Extend from Gujarat to Delhi

Western Ghats

-         Western edge of Deccan Plateau

-         Parallel to west coast

-         Continuous hills

-         Can be crossed only through passes like Thal Ghat, Pal Ghat, Bhor Ghat etc.

-         Higher than the Eastern Ghats

-         Average elevation 900 – 1600 meters; height increases from north to south

-         Anai Mudi (2,695 m) and Doda Betta (2,637 m) are the highest peaks

-         Cause orographic rain

Eastern Ghats

-         Average elevation 600 m

-         Mahendra Giri (1,501 m) is the highest peak

-         Stretch from the Mahanadi valley to the Nilgiris

-         Discontinuous, irregular

-         Dissected by rivers draining into the Bay of Bengal

-         Ooty (or Udagamandalam) in the Nilgiris and Kodaikanal in the Palani hills are famous hill stations in Tamil Nadu.

-         Shevroy hills and Javadi hills lie southeast of Eastern Ghats

The Indian Desert

-         A large, arid region in the northwestern part of India, mostly in India and partly in Pakistan

-         An undulating sandy plain with a poor vegetation cover

-         Covered with sand dunes (some longitudinal; some crescent-shaped called barchans)

-         Area 2,00,000 km²

-         9^th largest sub-tropical desert

-         Has the Aravallis on the east, the Rann of Kutch (a salt marsh) in the south and the Indus river on the west

-         Very low rainfall (below 15 cm per year)

-         Streams appear during the rainy season

-         The only large river is the Luni

Coastal Plains: Narrow coastal strips on either side of the peninsular plateau; sites for fishing and port activities

The Western Coast

-         Lies between the Arabian Sea and the Western Ghats

-         A narrow plain

-         The 3 sections: The Konkan coast (the northern part of the west coast from Mumbai to Goa), the Kannad Plain (the central part) and the Malabar coast (the southern part, in Kerala)

The Eastern Coast

-         Lies between the Bay of Bengal and the Eastern Ghats

-         A wider plain

-         The northern part of the eastern coast is called Northern Circar

-         The southern part is called the Coromandel Coast

-         Comprises deltas of the Mahanadi, the Godavari, the Krishna and the Kaveri

-         Lake Chilika on the east coast is India’s largest salt water lake. It is in Orissa, south of the Mahanadi delta

The Islands – Lakshadweep

-         Lie close to the Malabar coast of Kerala

-         Small coral islands

-         Earlier known as Laccadive, Minicoy and Amindive; renamed Lakshadweep in 1973

-         Area 32 km²

-         Administrative headquarters at Kavaratti

-         The Pitli island has a bird sanctuary

Coral polyps: Short-lived microscopic organisms which secrete a hard rock-like substance

Reef: A ridge of jagged rock formed from coral secretions and skeletons

Types of reefs: Barrier reef, fringing reef, atoll

Barrier reef: A coral reef running parallel to the shore

Fringing reef: A coral reef very close to the land

Atoll: A circular or horse-shoe shaped coral reef

The Great Barrier Reef: It is in Australia

Andaman and Nicobar Islands

-         Bigger in size than Lakshadweep

-         The northern part of the island group is called the Andamans and the southern part Nicobar

-         An elevated portion of submarine mountains

-         Some are of volcanic origin

-         Of great strategic importance

-         Close to the equator; have equatorial climate and thick forest cover

-         An active volcano exists on the Barren island in the Andamans