Introduction

Indias latitudinal and longitudinal extent is 30°. North-South distance is 3214 km and the east-west distance is 2933 km. North lies in subtropical and warm temperate regions and south lies in the tropics.

It is the 7^th largest country with 3.28 million sq km and 2.4% of the world’s land surface and 17% of the population. It has 6100 km of coast on the mainland and 7517 km along with the islands.

Gujarat has the longest coastline and Bangladesh shares the largest border with India. In all, there are 7 countries not counting Tibet that India shares a border.

Indira Point in the Nicobar Islands is the southernmost tip of India.

Physiography of India

• • Physiography deals with the study of the surface features and landforms of the Earth. On the basis of tectonic history, stratigraphy, and physiography, India may be divided into the following four physiographic divisions:

• • • The elevated Peninsular region

• • • The mighty Himalayas and their associated young folded mountains

• • • The Indo-Gangetic-Brahmaputra Plains

• • • The Coastal Plains and Islands.

Major Geological Formations of Peninsular India (about 3600 million years ago)

• • The North Central Highlands: They include First The Aravallis (It is one of the oldest folded mountains in the world). The Great Boundary Fault (GBF) separates the Aravallis from the Vindhyan Mountains. Secondly, Malwa Plateau has two drainage systems, one towards the Arabian Sea (Narmada, and Mahi], and another towards the Bay of Bengal (Chambal, Sind, Betwa, and Ken) joining the Yamuna river. Finally the Vindhyan ranges (Maikal Range forms a connecting link between the Vindhyans and the Satpura mountains).

• • The South Central Highlands: It has Bundelkhand and Vindhyachal-Baghelkhand or Vindhyachal Plateau.

• • Chotanagpur plateau: Plateau sprawls over parts of West Bengal, Jharkhand, Chhattisgarh, Odisha, and the northeastern part of Andhra Pradesh.

• • Meghalaya Plateau and Mikir Hills: Consisting of the Garo, Khasi, Jaintia hills and the outlying Milar and Rengma hills, it is a plateau that has been detached from the Indian Peninsula by the Malda Gap.

• • The North Deccan (Maharashtra Plateau): Plateau of Maharashtra includes the entire state of Maharashtra, except the Konkan coast and the Sahyadris.

• • The South Deccan

• • The Western Ghats: The Western Ghats or Sahyadris run parallel to the western coast for about 1600 km in the north-south direction from the mouth of the Tapi river to Kanyakumari (Cape Comorin). The western slope of Sahyadri is steep while the eastern slope is gentle. These are block mountains formed due to the down warping of a part of the land into the Arabian Sea

• • The Eastern Ghats

Physical Geography

The physical geography of India has four parts:

1.  Northern mountains.
2.  Northern plains.
3.  Peninsular plateau
4.  Coastal plains.

Northern mountain:

The northern mountain complex contains the Himalayas, Trans Himalayas, and Purvachal. The Himalayas are in the north, Hindukush, and Sulaiman is in the northwest, and Purvachal is in the east.

The Himalayas are true mountains. They are formed from the continent-continent plate collision. They have sediments of marine origin. It is not a single range but a series of ranges.

The Himalayas have three ranges namely the great Himalayas [Himadri], middle or lesser Himalayas [Himachal], and outer Himalayas [Shiwaliks].

 Fig 1: Himalayan range

 

Types of Himalayas

Greater Himalayas:

1.  Highest and most continuous mountain range in the world. The Greater Himalayas are almost a contiguous range. The range has very few gaps mainly provided by the antecedent rivers. The Greater Himalayas receive less rainfall as compared to the Lesser Himalayas and the Shiwaliks. Physical weathering is pronounced. Erosion is, however, less effective over the Greater Himalayas as compared to the Lesser Himalayas. Being lofty, they have very little forest area. The Greater Himalayas are about 25 km wide with an average height above 6100 metres
2.  Crystalline rocks.

Middle Himalayas:

1.  Less in height and discontinuous. The width of the Lesser Himalayas is about 80 km with an average height of 1300-4600 m. It consists, generally, of un-fossiliferous sediments or metamorphosed crystalline.

Outer Himalayas:

1. Upliftment of the foothills of the Himalayas. The Shiwaliks extend from Jammu Division of Jammu and Kashmir State to Assam. In width, Shiwaliks vary from 8 km in the east to 45 km in the west with an average elevation of about 900 – 1500 m above sea level. It is not a continuous range. It is broader in the west and narrows down In the east. Between the Shiwaliks and the Lesser Himalayas are longitudinal valleys called Doons / Duns.
2. They are created due to the alluvial deposit of the Himalayan rivers.

Structure of Himalayas:

1.  The middle bend is convex shape.
2.  Second sharp bend is towards southern end.
3.  Western bend towards Nanga Parbat and eastern towards Namcha Barwa.
4.  Northern side rests against Tibetan plateau and southern side is covered with snow. Gentle slope on northern side and steep slope on southern side.
5.  The mountains don’t act as a water divide but allow rivers to cut across. The rate of erosion by rivers is greater than the rate of upliftment of Himalayas.

Western Himalayas	Eastern Himalayas
Lower and gradual slope.	Higher and steep sudden slope.
Located on higher latitudes and so colder	Located on lower latitudes and so warmer
Don’t act as barrier to south west monsoon	Act as barrier to south west monsoon
Shiwaliks are farther	Shiwaliks are closer

                                          TABLE 1: EASTERN AND WESTERN HIMALAYAS

Region-wise division of Himalayas

The Himalayas are divided into five regions:

2.  Kashmir Himalayas
3. Karakoram, Ladakh, Zanskar, Pir Panjal and Dhauladhar are the ranges from north to south in that order. It has the largest number of glaciers in India.
4. Karewa formation – clay, sands from old fertile lands. Surrounded by the Greater Himalayas and the Lesser Himalayas is the Kashmir Valley. Having a height of 1585 m above sea level, the total area of the Kashmir Valley is about 4920 sq km. It is a structural longitudinal ‘Dun’. A special feature of the Vale of Kashmir is the Karewa (lacustrine) deposits consisting of silt, sand, and clay. These karewas are mainly devoted to the cultivation of saffron and have orchards of apple, peach, almond, walnut, and apricot. Kashmir Himalayas are characterized by high snow-covered peaks, deep valleys, interlocked spurs, and high mountain passes.
5.  Lake Wular – is the largest freshwater lake in India located in Kashmir.
6.  Kumaon Himalayas: The Kumaon Himalayas are connected to Tibet by a number of passes.
7. Garhwal and Kumaon hills from west to east.
8. Source of Ganga and Yamuna. Located in Uttarakhand.
9.  Nepal Himalayas
10. Tallest section of the Himalayas.
11.  Sikkim Himalayas: The highest peaks of the world like Mt. Everest (8850 m), Kanchenjunga {8598 m}, Makalu (8481 m), Dhaulagiri (8172 m), Annapurna (8078 m), Manaslu (8154 m) and Gosainath (8014 m) are situated in this part of the Himalayas. It has very few passes. The passes of Nathu-La and Jelep La (4538 min Sikkim) connect Gangtok (Sikkim) with Lhasa (Tibet, China).
12.  Assam Himalayas the southern border of Arunachal Pradesh, the Himalayas takes a southerly turn and the ranges are arranged in a north-south direction. Passing through the states of Arunachal Pradesh (Tirap Division) Nagaland, Marripur, Tripura, and Mizoram, the Himalayas are locally known as Purvachal. The Purvanchal is joined by the Meghalaya Plateau in the west. The extension of the Myanmar mountain chain continues southward up to Andaman and Nicobar Islands and even up to the Archipelago of Indonesia.

 Himalayas range isn’t stable like the western ghats

Debris, avalanches, and landslides occur frequently in the Himalayas as they are technically active, made up of sedimentary, unconsolidated, or semi consolidated rocks.

They have steep slopes.

Nilgiris are slightly tectonically stable and have hard rocks so landslides are less frequent. However direct rockfall is seen due to steep slopes, heavy rains, and mechanical weathering due to temperature and escarpments.

Dun:

When rivers are obstructed by mountains they spread out to form lakes. The lakes dry up when the rivers find paths through the mountains. These dried-up lakes are called “duns”. They are found between the great and middle Himalayas.

Importance of Himalayas:

1. Prevents cold Siberian winds from entering India.
2. The Himalayas are responsible for rainfall in the northeast. Also without them, there would be no Tibet plateau and India would have been a desert.
3. They split the subtropical jet streams into two bringing winter rain to India.
4. Source of perennial rivers.
5. Great forest and mineral wealth.

The Syntaxial Bends of the Himalayas

• • The general east-west trend of the Himalayas terminates suddenly at its western and eastern extremities and the ranges are sharply bent southward in deep knee-bend turns which are called syntaxial bends.

• • The western syntaxial bend is near Nanga Prabat where the Indus has cut a deep gorge.

• • There is a similar hairpin bend in Arunachal Pradesh where the mountains take a sharp bend from the eastern to southern direction after crossing the Brahmaputra river.

Main Passes of the Himalayas

• • Bomdi La:Connects Arunachal Pradesh with Lhasa, the capital of Tibet.

• • Dihang Pass: Connects Arunachal Pradesh with Mandalay (Myanmar).

• • Khardung La: Situated at an elevation of more than six thousand meters above sea level, it is the highest motorable pass in the country. It joins Leh with the Siachin glacier. The road remains closed during the winter season.

• • Lipu Lekh (Uttarakhand): Connects Uttarakhand with Tibet. The pilgrims for Mansarovar Lake travel through this pass

Purvanchal:

The mountains have the same orogeny as the main Himalayas. From north to south the mountains are patkai, naga, and Mizo hills. The elevation decreases from north to south.

Patkai hills – the border between Arunachal Pradesh and Myanmar.

Manipuri hills – the border between Manipuri and Myanmar. Manipur has loktak lake and Mizoram has molassis basin which is soft unconsolidated deposits.

Andaman and Nicobar islands are extensions of the eastern Himalayas.

Importance of Himalayas

• • Climatic Influence: The altitude of the Himalayas, their sprawl, and their extension intercept the summer monsoon coming from the Bay of Bengal and the Arabian Sea. They also prevent the cold Siberian air masses from entering India. Had there been no Himalayas, the whole of northern India would have been a desert. The Himalayas are responsible for the splitting of the jet streams into two branches, and these, in turn, play an important role in the arrival, success, and failure of the monsoons in India.

• • Defense: Throughout history, the foreign invaders never entered India from the northern side. Despite modern technology of warfare, the Himalayas have great defence value.

• • Source of Perennial Rivers: Most of the perennial rivers of northern India have their origin in the glaciers, lakes, and springs of the Himalayas.

• • Source of Fertile Soils: The perennial rivers and their tributaries carry enormous quantities of alluvial soils which are deposited in the Great Plains of India.

• • Generation of Hydro-electricity:

• • Forest Wealth: There is horizontal zonation of vegetation in the Himalayas. The natural vegetation in the Himalayas varies from the humid tropical to the conifers and alpine pastures. At the higher altitudes are the alpine pastures (margs) used by the tribals for grazing cattle during the summer season.

• • Orchards, minerals, tourism, and pilgrimage

Northern Plains:

Youngest physiographic feature in India. Depositional flood plain created by Himalayan rivers like Indus, Ganga, Brahmaputra and Yamuna.

Densely populated with 30% of the world’s population on 10% of the world’s agricultural land.

Part of the northern plains:

1. Babhar – alluvial fans of rivers with course boulders and not suitable for cultivation.
2. Khadar – new flood plains with very fertile soil
3. Bangar – old flood plains with calcerous kanker formation; less fertile
4. Terai – bad drainage with swampy land.

North plains are divided into four parts:

1.  Rajasthan plains

•  Formed west of Indus.
•  Drained by Luni which is located west of Aravalli
•  Thar desert is a tropical desert formed due to offshore trade winds and the Aravalli range is parallel to the southwest monsoon so no orographic rains.

2. Punjab plains
   

•  Drained by Ravi, Sutlej, Beas
•  Khadar plains are present but bad topography causes bad drainage.

3. Gangetic plains
4. Assam plains
   

•  Drained by Brahmaputra – the largest river of India by volume.

 Peninsular plateau:

It is covered by western ghats and eastern ghats and in the north by the central highlands. The Deccan traps were formed when the Indian plate flowed over reunion island. The basaltic flow has created a layer over layer and it looks like steps. It is higher than the northern plains.

Aravalli range: one of the oldest mountain ranges. It has sedimentary, metamorphosized rocks. Sabarmati from the eastern side of Aravali merges into the Arabian sea.

Vindhyan range: source of many north-flowing rivers that meet the Yamuna. It represents the water divide of central India. Mahi from the north side of Vindhya also is a west-flowing river.

Malawa plateau – between Aravalli and Vindhya range.

Satpuda range – has the Amarkantak plateau which is the source of Narmada and son.

Meghalaya plateau – Garo, Khasi, Jaintia hills, and Barail range in line. The hills aren’t very high so ineffective in blocking rain winds. These are blocked in Arunachal Pradesh.

Narmada and tapti are old rift valleys. The world’s largest freshwater lakes are rift valleys.

Western Ghats: UNESCO World Heritage Site

They are extending from Maharashtra to Kerela. In Maharashtra, they are steeper and higher. In Karnataka, they are broader. In Kerela, they are isolated hills with gaps that allow rain winds to pass through them.

The height of the Western ghats decreases from north to south.

The air parcel that passes over the hills retains energy but as they take longer the droplets precipitate into the rain.

Anaimudi is the highest peak in the Deccan.

Eastern Ghats

Discontinuous range but with lower heights in the mountains. Laterite soil is present. Coromandel’s coast lies between eastern Ghats and the Bay of Bengal.

The Bay of Bengal has 572 islands out of which 2 main islets are richies and labyrinth island.

Andaman and Nicobar are separated by the 10° channel and Lakshadweep by the 11° channel. Barren Island in Nicobar is India’s only active volcano.

Southern hill complex:

They are not a part of the western or eastern ghats. From north to south the hills are:

Nilgiri, Palani, Anamalai and Cardamom. Palghat pass between Nilgiri and Anamalai hills.

Nallamala, Javadi too are hill ranges in the south but above the above hills.

The western and the eastern ghats meet at Nilgiri hills.

Fig 5: Southern hill complex

Importance of the Deccan plateau:

1.  Oldest and most stable region.
2.  Rich in mineral wealth.
3.  98% of Gondwana coal
4.  Peninsular soil is black cotton soil or regur soil. Plantation of tea, coffee, rubber, cashews, and sugarcane.

Coastal Plain:

It extends from Rann of Kutch to Sunderbans. It has two parts western coastal plain and the eastern coastal plain.

 Western coastal plain:

1.  Narrower and steeper with fast-flowing rivers but no deposits.
2.  Rivers form estuaries not deltas.
3.  Good for port development
4.  Has two gulfs: kutchh and khambat.
5.  Coast are two: Konkan and Malabar.

Eastern coastal plain:

1.  Broader and with large rivers that form the delta.
2.  Chilika lake – is the biggest saltwater lake in India.