IX Geography Ch-2 India Physical Features

 

                                                               Geography Ch-2                                

India Physical Features

Tectonic plates

Earth scientists have put forward the view that the Earth’s crust   or the lithosphere is not a continuous block.

* It consists of several large and small, rigid, irregularly shaped plates (slabs) which include continents and the ocean floor.

*These slabs are moving or drifting in relation to each other by about 2.5 cm to 5 cm each year. These crustal slabs are called tectonic or lithospheric plates .

* Large fragments of earth’s crust are known as tectonic plates

* 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.

Asthenosphere

*Layer below the earth’s crust in which rocks are in semi molten state is known as asthenosphere

Movement of plates

There are three types of the plates

i) Convergent boundary:

*When plates come towards each other, the movement is known as convergent movement and form convergent boundary

*when two plates come  together they may either collide and crumble, or one may slide under the other.

ii) Divergent boundary:

Some plates move away from each other and form divergent boundary.

iii) Transform boundary: When tectonic plates move horizontally past each other, it is called transform boundary.

Physiographic divisions:

i.  The Himalayan Mountains

ii.  The Northern Plains

iii.  The Peninsular Plateau

iv.  The Indian Desert

v.  The Coastal Plains

vi The Island Groups

 

The physiographic divisions of India contemporary to each other in the following ways:

i.  The northern mountains are the major sources of water and forest wealth.

ii.  The  northern  plains  are  the  granaries  of  the  country.  They  provide  the  base  for  early civilizations

iii.  The  plateau  is  a  storehouse  of  minerals,  which  has  played  a  crucial  role  in  the

industrialisation of the country.

iv.  The coastal region and island groups provide sites for fishing and port activities.

Physical variation in India

* India is a vast country with varied landforms. It has high mountains, plains, plateaus, islands, deserts etc.

*This varied large landmass formed during different geological periods which has influenced her relief.

*Besides geological formations, a number of processes such as weathering, erosion and deposition have created and modified the relief to its present form.

*It is, therefore, India displays a great physical variation

Features of the Himalayan Mountains

*The Himalayas, geologically young and structurally fold mountains stretch over the northern borders of India. Their features are:

i. They form an arc, which covers a distance of about 2,400 km

ii. Their width varies from 400 km in Kashmir to 150 km in Arunachal Pradesh.

iii. The altitudinal variations are greater in the eastern half than those in the western half.

iv.  The Himalaya consists of three parallel ranges in its longitudinal extent; namely Himadri, Himachal and Shiwalik.

v. Himalaya is the source of many perennial rivers like ganga , Yamuna , Brahmaputra and Indus etc.it protects India from the cool winds coming from central Asia .

Features of the Himadri.

The northern most range of the Himalayas is known as the Greater or Inner Himalayas or the ‘Himadri’. Its features are:

i.  It is the most continuous range  with an average height of 6,000 metres.

ii.  It contains all the prominent Himalayan peaks like Mount Everest and Kanchenjunga.

iii.  The  folds  of  Great  Himalayas  are  asymmetrical  in  nature.  The  core  of  this  part  of Himalayas is composed of granite.

iv. This range is always covered with snow , and a number of glaciers descend from this range.

Features of the Himachal

The range lying to the south of the Himadri forms the most rugged mountain system and is known as Himachal or lesser Himalaya. Its features are:

i.  The ranges are mainly composed of highly compressed and altered rocks.

ii.  The altitude varies between 3,700 and 4,500 metres and the average width is 50 k.m.

iii.  The Pir Panjal range forms the longest and the most important range, the Dhaula Dhar and the Mahabharat ranges are also prominent ones.

iv.  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 .It snows here in winter.

Shiwaliks

 The outer most range of the Himalayas is called the Shiwaliks. Their main features are:

i. They extend over a width of 10-50 km its height varies between  900 and 1100 metres.

ii. These ranges are composed of unconsolidated sediments brought down by rivers from the main Himalayan ranges located farther north. Hence they are prone to landslides.

iii. These valleys are covered with thick gravel and alluvium.

iv. The longitudinal valley lying between lesser Himalaya and the Shiwaliks are known as Duns. Dehra Dun, Kotli Dun and Patli Dun are some of the well-known Duns.

Shiwaliks are prone to landslide since they are composed of unconsolidated sediments.

Division of Himalayas from west to east

*The Himalayas have been divided on the basis of regions from west to east. These divisions have been demarcated by river valleys.

(i) The part of Himalayas lying between Indus and Sutlej has been traditionally known as Punjab Himalayas. It is also regionally known as Kashmir Himachal Himalaya from west to east respectively.

(ii) The part of Himalayas lying between Sutlej and Kali rivers is known as Kumaon Himalayas.

(iii) The Kali and Tista rivers demarcate the Nepal Himalayas and the part lying between Tista and Dihang rivers is known as Assam Himalayas.

Purvanchal

*The eastern hills and mountains of the Himalayas running along the eastern boundary of Indiaare known as Purvanchal.

*They are located in the northeastern states of India.

 *They  are mostly composed of strong sandstone, a sedimentary rock. The Purvanchal are of medium height. The hills and ranges are covered with dense forests.

Some important hills of the Purvanchal are :

(i) the Patkai Bum and Naga hills

(ii) the Mizo hills and Manipur hills

(iii) the Garo, Khasi and Jaintia hills along Meghalaya-Bangladesh border.

(iv) the Dafla hills in the north.

Questions

1. Explain the theory of plate tectonics.

1.B Explain the plate movements .

2.Land of India is characterized by a great diversity in its relief or physical features justify this statement

The relief of India displays a great physical variation. Explain.

3.Write a short note on Himalaya mountain

4.Write any four features of Himalayas.

Northern plains

The features of the northern plains are:

i.  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.

ii.  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.

iii.  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.

Iv – it is densely populated physiographic unit of India

iv.  The Northern Plain is broadly divided into three sections.

Division according to relief features

*According to the variations in relief features, the Northern plains can be divided into four regions.

They are:

i.  Bhabar: 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.

ii.  Terai: South  of  the  bhabar  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.

iii.  Bhangar:  The  largest  part  of  the  northern  plain  is  formed  of  older  alluvium.  They  lie above the flood plains of the rivers and present a  terrace like feature. This part is known as bhangar. The soil in this region contains calcareous deposits locally known as kankar.

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

Western Ghats

*Western  Ghats  lie  parallel  to  the western coast.

*They  are  continuous  and  can  be crossed through passes only                                                   

iii.  The  Western  Ghats  are  higher  than the  Eastern  Ghats.  Their  average elevation is 900– 1600 metres

iv.  The  highest  peaks  include  the  Anai Mudi  (2,695metres)  and  the  Doda Betta (2,637metres).

v. it obstructs  monsoon winds coming from the Arabian Sea which causes heavy rainfall in the Western Coastal Plain.

Eastern Ghats

i.  Eastern Ghats  lie  parallel  to  the eastern coast.

ii.  They  are  discontinuous  and  are dissected  by  rivers  draining  into  the Bay of Bengal.

iii.  The Eastern Ghats are lower than the Western  Ghats.  Their  average elevation is 600 metres

iv.  Mahendragiri  (1,501  metres)  is  the highest peak in the Eastern Ghats.

 v . They are almost parallel to the monsoons originating in the Bay  of Bengal and do not cause much rainfall.

Questions

1.Describe the Northern Great Plains of India.

2.Which three river systems form the northern plains of India ?mention main features.

3.How did the northern plains come into existence ?write two points briefly. Also mention two features of these plains .

4.Name the three sections into which northern plains has been divided .write one feature of each.

The features of the Indian desert are:

i.  The Indian desert lies towards the western margins of the Aravali Hills.

ii.  It is an undulating sandy plain covered with sand dunes called barchans

iii.  This  region  receives  very  low  rainfall  below  150  mm per  year  (15  cm)  .

iv. It  has  arid climate with low vegetation cover.

v.  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.

The Peninsular Plateau

1.Geologically, the Peninsular Plateau is part of the Gondwanaland, the southern part of ancient super-continent Pangaea.

2. The Peninsular plateau is part of oldest landmass.

3. It is one of the most stable land blocks.it is triangular in shape

4. It is a plateau or tableland with gently rising rounded hills and wide shallow valleys.

5. The Peninsular Plateau is composed of old crystalline igneous and metamorphic rocks.

6. The Peninsular Plateau is divided mainly into two broad divisions :

(i)the Central Highlands and (ii) the Deccan Plateau.

7. A distinct feature of the Peninsular Plateau is the black soil area known as Deccan Trap. This soil is ideal for growth of cotton

8.It has moderate density of population.

Deccan Plateau.

* The part of the Peninsular Plateau lying to the south of river Narmada is known as Deccan Plateau.

*It is a triangular landmass with broad base in the north and tapers southward.

* It is formed due to lava flows, so a greater part of it is composed of basaltic rocks of volcanic origin.

*It is flanked by the Satpura range in the north. The Mahadev, the Kaimur hills and Maikal range form its eastern extensions. The Deccan Plateau is flanked by the Western Ghats in the west and Eastern Ghats in the east.

*The plateau is higher in the west and slopes gently eastwards. The black soil area of the Deccan Plateau is known as Deccan Trap.

The Central Highlands

*The part of the Peninsular plateau lying to the north of the Narmada river is known as Central Highlands.

*It comprises of Malwa Plateau, Bundelkhand and Baghelkhand plateaus, the Vindhya Range and extends as Chhota Nagpur Plateau.

*The  eastward  extensions  of  this  plateau  are  locally known  as  the  Bundelkhand  and Baghelkhand.

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

*The Vindhyan range is bounded by the Central Highlands on the south and the Aravali range on the northwest.

 *The Aravalis are highly denuded old hills that lie on the western and northwestern margins of the Peninsular Plateau.

The Coastal plains

 These are narrow coastal strips, running along the Arabian Sea on the west and the Bay of Bengal on the east.

i) The Western Coastal Plain: It is 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.

 

ii) The Eastern Coastal Plain: The plain along theBay 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 Coromandal Coast.

* Large rivers such as the Mahanadi, the Godavari, the Krishna and the  Kaveri  have  farmed  extensive   delta  on  this  coast.  Lake  Chilika  is  an  important feature along the eastern coast

The Islands

*The Lakshadweep Islands group in the Arabian Sea is close to Kerala.

*The Lakshadweep Islands were formerly known as Laccadive, Minicoy and Amindive..the Kavaratti island is the capital of Lakshadweep

*It consists of many small islands  Lakshadweep Islands  have coral origin.

*These coral deposits called ‘atolls’ in Malayalam which refer to their ring or ‘horse-shoe’ shape.

*They are 27 in number and 17 islands are uninhabited

                                                             

The Andaman and Nicobar Islands are an elongated chain of islands located in the Bay of Bengal.

*The Andamans and Nicobar Islands are an elevated portion of submarine mountains

There are about 200 islands in the Andaman group and 19 islands in the Nicobar group.

 

*These  Islands,are larger in size , more in number and more widely scattered.

*Corals are shortlived microscopic organisms, which lives in colonies.

*They flourish in shallow, mud-free and warm waters. They secrete calcium carbonate. The coral secretion and their skeletons form coral deposits.

Lakshadweep islands group lying close to the Malaber Coast of Kerala is composed of small coral islands.                                           

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