Chapter Notes and Summary
1. India is a vast country with varied landforms i.e., mountains, plains, deserts, plateaus and islands.
2. India is a large landmass formed during different geological periods which has influenced her relief.
• Theory of Tectonic Plates
1. According to ‘‘Theory of Plate Tectonics’’ crust
(upper part) of Earth has been formed out of seven major and some minor plates.
2. movement of plates resulted in building up of stresses within plates leading to folding, faulting and volcanic activity.
3. 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 transform boundary.
4. movements of these plates have changed position and size of continents over millions of years.
5. Such movements have also influenced evolution of present landform features of India.
6. oldest landmass (the Peninsular part) was a part of Gondwana land in ancient times.
7. Gondwana land included India, Australiar, South Africa and South America as one single landmass.
8. Convectional currents split crust of Earth into a number of pieces, thus leading to drifting of Indo-Australian plate towards North after being separated from Gondwana land.
9. northward drift resulted in collision of plate with much larger Eurasian plate.
10. Due to collision, sedimentary rocks which were accumulated in geocyncline, got folded form of mountain systems of Western Asia and Himalayas.
• Northern Plains
1. Himalayan uplift of Tethys sea and subsidence of northern flank of peninsular plateau resulted in formation of a large basin.
2. Gradually, basin got filled with deposition of sediments by rivers flowing from mountains in north and peninsular plateau in south.
3. A flat land of extensive alluvial deposits led to formation of northern plains.
• Major Physiographic Divisions
1. Himalayan Mountains
2. Northern Plains
3. Peninsular Plateau
4. Indian Desert
5. Coastal Plains
7. Himalayas are geologically young and structurally fold mountains. They stretch across northern borders of India.
8. They are longest range in India, covering an arc of about 2,400 km.
9. These mountain ranges run in a West-East direction from Indus to Brahmaputra.
10. Himalayas consist of three parallel ranges in its longitudinal extent.
11. northernmost range is known as Great or Inner Himalayas or ‘Himadri’. It is a continous range with an average height of 6,000 metres. It contains all prominent Himalayan peaks.
12. core of this part of Himalayas is composed of granite.
13. Himachal or lesser Himalayas lie to South of Himadri.
14. altitude in lesser Himalayas varies between 3,700
and 4,500 metres and average width is 50 km.
15. Pir Panjal range forms longest and most important range in these Hills. Dhaula Dhar and Mahabharat ranges are also prominent ones here.
16. This range consists of famous Valley of Kashmir, Kangra and Kullu Valley in Himachal Pradesh.
• Shiwaliks outermost range of Himalayas is called Shiwaliks.
1. They extend over a width of 10-50 km and have an altitude varying between 900 and 1100 metres.
2. longitudinal valleys lying between lesser Himalayas and Shiwaliks are known as Duns. Dehra Dun, Kotli Dun, etc.
3. This range is composed of unconsolidated sediments brought down by rivers.
4. Himalayas have also been divided on basis of regions from West to East. These regions have been demarcated by river valleys. e.g., 5. Punjab Himalayas – lie between Indus and Satluj rivers.
6. Kumaon Himalayas – lie between Satluj and Kali rivers.
7. Nepal Himalayas – lie between Kali and Tista rivers.
8. Assam Himalayas – lie between Tista and Dihang rivers.
9. There are some regional names also of Himalayas.
10. Beyond Dihang gorge Himalayas bend sharply to South and spread along eastern boundary of India.
They are known as Purvachal or Eastern hills and mountains.
11. These hills running through north-eastern states are mostly composed of sedimentary rocks covered with dense forests.
12. Purvachal comprises of Patkai hills Naga hills, Manipur hills and Mizo hills.
• Northern Plain
1. Northern plains has been formed by interplay of
3 major river systems namely Indus, Ganga and Brahmaputra along with their tributaries.
2. This plain is formed of alluvial soil deposited in a vast basin over millions of years.
3. It spreads in an area of 7 lakh sq km.
4. plain is 2400 km long and 240-320 km broad.
5. It is densely populated with a rich soil, adequate water supply and favourable climate. It is agriculturally a very productive part of India.
4. Northern plain is broadly divided into 3 sections.
These are Punjab plains, Ganga plains and Brahmaputra plains.
• Punjab Plains
1. Western part of Northern plains is referred to as Punjab plains.
2. Formed by Indus and its tributaries, a large part of this plain lies in Pakistan.
3. Indus and its tributaries, Jhelum, Chenab, Ravi, Beas and Satluj originate in Himalayas. This section of plain is dominated by Doabs.
• Ganga Plains
1. Ganga plains extends between Ghaggar and Teesta rivers.
2. It is spread over states of Haryana, Delhi, UP, Bihar, partly Jharkhand and West Bengal.
• Brahmaputra Plains
1. To east of Ganga plains lies Brahmaputra plains
2. This lies mostly in Asom
• Division of Northern Plains on Basis of Relief Features Northern plains also have diverse relief features. These are
(a) Bhabar rivers, after coming down from mountains, deposit pebbles in a narrow area which is lying parallel to slopes of Shiwaliks. It is known as Bhabar. All streams disappear in Bhabar belt.
(b) Terai Belt
The streams and rivers re-emerge and create a wet swampy and marshy region known as Terai.
The Terai region is a thickly forested region full of wildlife.
The largest part of Northern plains is formed of older alluvium. Bhangar lies above flood plains of rivers and present a terrace like feature.
This soil contains calcareous deposits locally known as Kankar.
The newer and younger deposits of flood plains are called Khadar.
They are renewed almost every year so they are fertile and thus ideal for intensive agriculture.
• Peninsular Plateau
1. Peninsular plateau is a table land composed of old crystalline igneous and metamorphic rocks.
2. It was formed due to breaking and drifting of Gondwana land thus making it a part of oldest landmass.
3. This plateau consists of two broad divisions, namely central highlands and Deccan plateau.
• Central Highlands
1. part of Peninsular plateau lying to North of Narmada river covering a major area of Malwa plateau is known as central highlands.
2. Vindhyan range bounds central highlands on South and Aravalis on North-West.
3. flow of rivers draining this region, namely Chambal, Sind, Ken and Betwa is from South-West to North East.
4. central highlands are wider in West but narrower in East.
5. eastward extensions of this plateau are locally known as Bundelkhand and Baghelkhand.
6. Chhotanagpur plateau marks further eastward extension, and is drained by Damodar river.
7. Deccan plateau is a triangular landmass that lies to south of Narmada river.
8. Satpura range flanks its broad base in North while Mahadev, Kaimur and Maikal range form its Eastern extensions.
9. An extension of plateau is also visible in North-East locally known as Meghalaya Karbi-Anglong plateau and North Cachar hills.
10. Three prominent hill ranges in Meghalaya from west to east are Garo, Khasi and Jaintia hills.
• Western Ghats
1. Western Ghats lie parallel to Western coast.
2. They are continuous and can only be crossed through passes .
3. Western Ghats are higher than Eastern Ghats.
4. Their average elevation is 900-1600 metres as against
600 metres of Eastern Ghats.
5. height of Western Ghats progressively increases from North to south.
6. highest peaks include Annai Mudi (2,695 metres and Doda Betta (2,637 metres). Western Ghats cause orographic rain by facing rain bearing moist winds.
• Eastern Ghats
1. Eastern Ghats stretch from Mahanadi Valley to Nilgiris in South.
2. Eastern Ghats are discontinuous, irregular and dissected by rivers draining into Bay of Bengal.
3. Mahendragiri (1501 metres) is highest peak in Eastern Ghats.
4. They have hill stations of Udagamandalam (popularly known as Ooty) and Kodaikanal, both in Tamil Nadu.
5. Eastern Ghats mark Eastern edge of Deccan plateau.
6. average height of Eastern Ghats is 600 metres.
• Indian Desert
1. Indian desert lies towards eastern margins of Aravali hills.
2. It is an undulating sandy plain covered with sand dunes.
3. This region receives very low rainfall, below 150 mm per year.
4. It has arid climate with low vegetation cover.
5. Streams appear during rainy season.
6. Soon after, they disappear into sand as they do not have enough water to reach sea.
7. Luni is only large river in this region.
8. Barchans (crescent shaped dunes) cover large areas but longitudinal dunes become more prominent near India-Pakistan border.
• Coastal Plains
1. Peninsular plateau is flanked by stretches of narrow coastal strips, running along Arabian Sea on west and Bay of Bengal on east.
2. western coast sandwiched between Western Ghats and Arabian Sea is a narrow plain. It consists of three sectors.
3. northern part of coast is called Konkan (Mumbai –
Goa). central stretch is called Kannad plain while southern stretch is referred to as Malabar coast.
4. plains along Bay of Bengal are wide and level. In northern part it is referred to as Northern Circar, while southern part is known as Coromandel coast.
5. Large rivers such as Mahanadi, Godavari, Krishna and Kaveri have formed extensive deltas on this coast.
6. Lake Chilka is an important feature along Eastern coast.
1. India has two groups of islands.
2. Lakshadweep Islands group is lying close to Malabar coast of Kerala.
3. This group of islands is composed of small coral islands.
4. Earlier they were known as Laccadive, Minicoy and Anainative. In 1973, they were named as Lakshadweep.
5. They coverts a small area of 32 sq km.
6. Kavaratti Island is administrative headquarters of lakshadweep.
7. This island group has great diversity of flora and fauna.
Pitti island, which is uninhabited, has a bird sanctuary.
• Andaman and Nicobar Islands
1. elongated chain of islands located in Bay of Bengal extending from north to south are Andaman and Nicobar Islands.
2. They are bigger in size and more numerous and scattered, compared to Lakshadweep.
3. entire group of islands is divided into two broad categories. Andaman in North and Nicobar in South.
4. It is believed that these islands are an elevated portion of submarine mountains.
5. These islands are of great strategic importance for country.
6. There is great diversity of flore and fauna on this island group.
7. islands lie close to equator and experience equatorial climate and have thick forest cover.
Chapter Notes and Summary