2.1. Geological Divisions of India
Based on the variations in its geological structure and formations, India can be divided into three geological divisions as follows:
- The Peninsular Block
- The Himalayas and other Peninsular Mountains
- Indo-Ganga-Brahmaputra Plain.
2.1.1. The Peninsular Block
- The northern boundary of the Peninsular Block may be taken as an irregular line running from Kachchh along the western flank of the Aravali Range near Delhi and then roughly parallel to the Yamuna and the Ganga as far as the Rajmahal Hills and the Ganga delta. Apart from these, the Karbi Anglong and the Meghalaya Plateau in the northeast and Rajasthan in the west are also extensions of this block.
- The northeastern parts are separated by the Malda fault in West Bengal from the Chotanagpur plateau. In Rajasthan, the desert and other desert–like features overlay this block.
- The Peninsula is formed essentially by a great complex of very ancient gneisses and granites, which constitutes a major part of it. Since the Cambrian period, the Peninsula has been standing like a rigid block with the exception of some of its western coast which is submerged beneath the sea and some other parts changed due to tectonic activity without affecting the original basement.
- As a part of the Indo-Australian Plate, it has been subjected to various vertical movements and block faulting. The rift valleys of the Narmada, the Tapi and the Mahanadi and the Satpura block mountains are some examples of it. The Peninsula mostly consists of relict and residual mountains like the Aravali hills, the Nallamala hills, the Javadi hills, the Veliconda hills, the Palkonda range and the Mahendragiri hills, etc.
- The river valleys here are shallow with low gradients. Most of the east flowing rivers form deltas before entering into the Bay of Bengal. The deltas formed by the Mahanadi, the Krishna, the Kaveri and the Godavari are important examples.
2.1.2. The Himalayas and Other Peninsular Mountains
- The Himalayas along with other Peninsular mountains are young, weak and flexible in their geological structure unlike the rigid and stable Peninsular Block. Consequently, they are still subjected to the interplay of exogenic and endogenic forces, resulting in the development of faults, folds and thrust plains.
- These mountains are tectonic in origin, dissected by fast-flowing rivers which are in their youthful stage. Various landforms like gorges, V-shaped valleys, rapids, waterfalls, etc. are indicative of this stage.
2.1.3. Indo-Ganga-Brahmaputra Plain
- The third geological division of India comprises the plains formed by the river Indus, the Ganga and the Brahmaputra.
- Originally, it was a geo-synclinal depression which attained its maximum development during the third phase of the Himalayan mountain formation approximately about 64 million years ago. Since then, it has been gradually filled by the sediments brought by the Himalayan and Peninsular rivers.
- Average depth of alluvial deposits in these plains ranges from 1,000-2,000 m.
2.2. Major Physiographic Divisions of India
- Physiography is that branch of science which studies the present relief features of the earth surface or of natural features in their causal relationships.
- Physiography of an area is the outcome of structure, process and the stage of development.
- The land of India is characterized by great diversity in its physical features. The north has a vast expanse of rugged topography consisting of a series of mountain ranges with varied peaks, beautiful valleys and deep gorges.
- The south consists of stable table land with highly dissected plateaus, denuded rocks and developed series of scarps. In between these two lie the vast north Indian plain. Based on these macro variations, India can be divided into the following physiographic divisions:
- The Northern and Northeastern Mountains
- The Northern Plain
- The Peninsular Plateau
- The Indian Desert
- The Coastal Plains
- The Islands.
The Northern and Northeastern Mountains
- The North and Northeastern Mountains consist of the Himalayas and the Northeastern hills. The Himalayas consist of a series of parallel mountain ranges. Some of the important ranges are the Greater Himalayan range, which includes the Great Himalayas and the Trans-Himalayan range, the middle Himalayas and the Shiwalik.
- The general orientation of these ranges is from northwest to the southeast direction in the northwestern part of India. Himalayas in the Darjeeling and Sikkim regions lie in an east-west direction, while in Arunachal Pradesh they are from southwest to the northwest direction. In Nagaland, Manipur and Mizoram, they are in the north-south direction.
The Himalayas: The Himalayas, geologically young and structurally folded mountains stretch over the northern borders of India. These mountain ranges run in a west-east direction from the Indus to the Brahmaputra. The Himalayas represent the loftiest and one of the most rugged mountain barriers of the world. They form an arc, which covers a distance of about 2,400 Km. their width varies from 400 Km in Kashmir to 150 Km in Arunachal Pradesh. The altitudinal variations are greater in the eastern half than those in the western half.
Longitudinal Divisions of Himalayas
The Himalaya consists of three parallel ranges in its longitudinal extent and Trans-Himalayas. A number of valleys lie between these ranges.
The Greater Himalayas or Himadri
- The northernmost range is known as the Great or Inner Himalayas or the ‘Himadri’. It is the most continuous range consisting of the loftiest peaks with an average height of 6,000 metres.
- It contains all the prominent Himalayan peaks. The folds of Great Himalayas are asymmetrical in nature. The core of this part of Himalayas is composed of granite.
- It is perennially snowbound, and a number of glaciers descend from this range.
The Lesser Himalaya or Himachal
- The range lying to the south of the Himadri forms the most rugged mountain system and is known as Himachal or lesser Himalaya.
- The ranges are mainly composed of highly compressed and altered rocks.
- The altitude varies between 3,700 and 4,500 metres and the average width is 50 Km. While the Pir Panjal range forms the longest and the most important range, the Dhaula Dhar and the Mahabharat ranges are also prominent ones.
- 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.
The Sub-Himalayas or Shiwaliks
- The outermost range of the Himalayas is called the Shiwaliks.
- They extend over a width of 10-50 Km and have an altitude varying between 900 and 1100 metres.
- These ranges are composed of unconsolidated sediments brought down by rivers from the main Himalayan ranges located farther north.
- These valleys are covered with thick gravel and alluvium.
- The longitudinal valley lying between lesser Himalaya and the Shiwaliks are known as Duns. DehraDun, Kotli Dun and Patli Dun are some of the well-known Duns.
- The Trans-Himalaya zone with a width of 40km in its eastern and western ends and a width of 222km in its central part, it has important ranges such as the Zaskar Range and the Great Karakoram range.
- The Karakoram extends towards the south-east to form the Kailash Range in Tibet. The highest peak in the karakoram range is K2 (8611m).
- The longest glacier is Siachen in the Nubra Valley which is more than 72km.
Regional Divisions of Himalayas
There are large-scale regional variations within the Himalayas. On the basis of relief, alignment of ranges and other geomorphological features, the Himalayas can be divided into the following subdivisions:
- Kashmir or Northwestern Himalayas
- Himachal and Uttaranchal Himalayas
- Darjeeling and Sikkim Himalayas
- Arunachal Himalayas
- Eastern Hills and Mountains or Purvanchal Hills.
Kashmir or Northwestern Himalayas
- It comprises a series of ranges such as the Karakoram, Ladakh, Zaskar and Pir Panjal. The northeastern part of the Kashmir Himalayas is a cold desert, which lies between the Greater Himalayas and the Karakoram ranges.
- Between the Great Himalayas and the Pir Panjal range, lies the world-famous valley of Kashmir and the famous Dal Lake. Important glaciers of South Asia such as the Baltoro and Siachen are also found in this region.
- The Kashmir Himalayas are also famous for Karewa formations, which are useful for the cultivation of Zafran, a local variety of saffron.
- Some of the important passes of the region are Zoji La on the Great Himalayas, Banihal on the Pir Panjal, Photu La on the Zaskar and Khardung La on the Ladakh range.
- Some of the important fresh lakes such as Dal and Wular and salt water lakes such as Pangong Tso and Tso Moriri are also in this region.
- This region is drained by the river Indus, and its tributaries such as the Jhelum and the Chenab.
- The Kashmir and northwestern Himalayas are well-known for their scenic beauty and picturesque landscape. The landscape of the Himalayas is a major source of attraction for adventure tourists. Some famous places of pilgrimage such as Vaishno Devi, Amarnath Cave, Charar -e-Sharif, etc. are also located here.
- Srinagar, capital city of the state of Jammu and Kashmir is located on the banks of Jhelum river. Dal Lake in Srinagar presents an interesting physical feature. Jhelum in the valley of Kashmir is still in its youth stage and yet forms meanders – a typical feature associated with the mature stage in the evolution of fluvial landform.
- The southernmost part of this region consists of longitudinal valleys known as ‘duns. Jammu dun and Pathankot dun are important examples.
Himachal and Uttaranchal Himalayas
- This part lies approximately between the Ravi in the west and the Kali (a tributary of Ghagra) in the east. It is drained by two major river systems of India, i.e. the Indus and the Ganga. Tributaries of the Indus include the river Ravi, the Beas and the Satluj, and the tributaries of Ganga flowing through this region include the Yamuna and the Ghaghara.
- The northernmost part of the Himachal Himalayas is an extension of the Ladakh cold desert, which lies in the Spiti subdivision of district Lahul and Spiti.
- All the three ranges of Himalayas are prominent in this section also. These are the Great Himalayan range, the Lesser Himalayas (which is locally known as Dhaoladhar in Himachal Pradesh and Nagtibha in Uttaranchal) and the Shiwalik range from the North to the South.
- In this section of Lesser Himalayas, the altitude between 1,000-2,000m specially attracted to the British colonial administration, and subsequently, some of the important hill stations such as Dharamshala, Mussoorie, Shimla, Kaosani and the cantonment towns and health resorts such as Shimla, Mussoorie, Kasauli, Almora, Lansdowne and Ranikhet, etc. were developed in this region.
- The two distinguishing features of this region from the point of view of physiography are the ‘Shiwalik’ and ‘Dun formations’. Some important duns located in this region are the Chandigarh-Kalka dun, Nalagarh dun, DehraDun, Harike dun and the Kota dun, etc. DehraDun is the largest of all the duns with an approximate length of 35-45 km and a width of 22-25 km.
- In the Great Himalayan range, the valleys are mostly inhabited by the Bhotia’s. These are nomadic groups who migrate to ‘Bugyals’ (the summer glasslands in the higher reaches) during summer months and return to the valleys during winters. The famous ‘Valley of flowers’ is also situated in this region. The places of pilgrimage such as the Gangotri, Yamunotri, Kedarnath, Badrinath and Hemkund Sahib are also situated in this part. The region is also known to have five famous Prayags (river confluences).
The Darjeeling and Sikkim Himalayas
- They are flanked by Nepal Himalayas in the west and Bhutan Himalayas in the east.
- It is relatively small but is a most significant part of the Himalayas. Known for its fast-flowing rivers such as Tista, it is a region of high mountain peaks like Kanchenjunga (Kanchan Giri), and deep valleys.
- The higher reaches of this region are inhabited by Lepcha tribes while the southern part, particularly the Darjeeling Himalayas, has a mixed population of Nepalis, Bengalis and tribals from Central India.
- As compared to the other sections of the Himalayas, these along with the Arunachal Himalayas are conspicuous by the absence of the Shivalik formations. In place of the Shiwaliks here, the ‘duar formations’ are important, which have also been used for the development of tea gardens.
- Sikkim and Darjeeling Himalayas are also known for their scenic beauty and rich flora and fauna, particularly various types of orchids.
The Arunachal Himalayas
- These extend from the east of the Bhutan Himalayas up to the Diphu pass in the east. The general direction of the mountain range is from southwest to northeast. Some of the important mountain peaks of the region are Kangtu and Namcha Barwa.
- These ranges are dissected by fast-flowing rivers from the north to the south, forming deep gorges. Bhramaputra flows through a deep gorge after crossing Namcha Barwa. Some of the important rivers are the Kameng, the Subansiri, the Dihang, the Dibang and the Lohit. These are perennial with the high rate of fall, thus, having the highest hydro-electric power potential in the country.
- An important aspect of the Arunachal Himalayas is the numerous ethnic tribal communities inhabiting these areas. Some of the prominent ones from west to east are the Monpa, Daffla, Abor, Mishmi, Nishi and the Nagas.
- This region is rich in biodiversity which has been preserved by the indigenous communities. Due to rugged topography, the inter-valley transportation linkages are nominal. Hence, most of the interactions are carried through the duar region along the Arunachal-Assam border.
The Eastern Hills and Mountains or Purvanchal Hills
- These are part of the Himalayan mountain system having their general alignment from the north to the south direction.
- They are known by different local names. In the north, they are known as Patkai Bum, Naga hills, the Manipur hills and in the south as Mizo or Lushai hills. These are low hills, inhabited by numerous tribal groups practicing Jhum cultivation.
- Most of these ranges are separated from each other by numerous small rivers. The Barak is an important river in Manipur and Mizoram.
- The physiography of Manipur is unique by the presence of a large lake known as ‘Loktak’ lake at the centre, surrounded by mountains from all sides.
- Mizoram, which is also known as the ‘Molasses basin’, is made up of soft unconsolidated deposits.
- Most of the rivers in Nagaland form the tributary of the Brahmaputra. While two rivers of Mizoram and Manipur are the tributaries of the Barak river, which in turn is the tributary of Meghna; the rivers in the eastern part of Manipur are the tributaries of Chindwin, which in turn is a tributary of the Irrawaddy of Myanmar.
The Great Himalayan range is also divided into following categories:
- The Punjab Himalayas: The 560km long stretch of the Himalayas between the Indus and the Sutlej rivers is known as the Punjab Himalayas. A large portion of this sector lies in Jammu and Kashmir and Himachal Pradesh as a result of which it is also called Kashmir and Himachal Himalaya.
- Kumaon Himalayas: This section extends from Sutlej to Kali river valleys and is said to have 360 lakes, such as NainiTal and Bhim Tal. The Pilgri-mages centers (Badri-nath, Gangotri) located in his section is of particular importance to Hindus
- Nepal Himalayas: This secti-on extends from Kali river to Tista and has the distinction of having some of the highest peaks in the world including Mt. Everest.
- Assam Himalayas: This section extends from Tista to Bra-hmaputra. The highest peak in this range is Namcha Barwa.
Important Passes of Himalayas
- Aghil Pass: Lies between Ladakh and Sinkiang
- Balcha Dhura: Connecting Uttarakhand with Tibet
- Banihal Pass (Jawahar Tunnel): Connects Banihal town and Qazigund town of Anantnag
- Baralacha La: Between Kyelan and Leh in Ladakh
- Bum La: Connects Arunachal Pradesh and Lhasa
- Chang La: Connects Ladakh with Tibet
- Diphu Pass: Between ArunachalPradesh and Myanmar
- Jelep La: Between Gangtok (Sikkim) and Tibet
- Karakoram Pass: Between Ladakh and Sinkiang
- Khardung La: Between Leh and Siachen Glaciers through Nubra Valley
- Lipu Lekh Pass: Between Uttarakhand and Tibet
- Muna Pass: Between Uttarakhand and Tibet
- Nathu La: Between Sikkim and Tibet entry to Chumbi Valley
- Rohtang Pass: Between Kullu and Kyelang in Himachal Pradesh
- Shipki La: Rivers Sutlej enters India from Tibet in Himachal Pradesh
The Significance of Himalayas
- Climatic Influence: The Himalayas play a very significant role in influencing the climate of India. By virtue of their high altitude, length and direction, they effectively intercept the summer monsoons coming from the Bay of Bengal and Arabian Sea and cause precipitation in the form of rain or snow. Besides, they prevent the cold continental air masses of central Asia from entering into India. Had there been no Himalayas, the whole of India would have been a desert in the absence of precipitation and its winters would have been very severe under the influence of cold air masses coming from Central Asia. According to the latest meteorological studies, the Himalayas are responsible for splitting the jet stream into two branches and these in turn play an extremely important role in bringing monsoons in India.
- Defence: The Himalayas have been protecting India from outside invaders since the early times thus serving as a defence barrier. But the Chinese aggression on India in October, 1962 has reduced the defence significance of the Himalayas to a considerable extent. In spite of advancement in modern warfare technology, the defence significance of the Himalayas cannot be ignored altogether.
- Source of Perennial Rivers: Almost all the great rivers of India have their sources in the Himalayan ranges. Abundant rainfall and vast snow-fields as well as large glaciers are the feeding grounds of the mighty rivers of India. Snow melt in summer provides water to these rivers even during dry season and these are perennial rivers. The Himalayan Rivers, along with hundreds of their tributaries, form the very basis of life in the whole of north India.
- Fertile Soil: The great rivers and their tributaries carry enormous quantities of alluvium while descending from the Himalayas. This is deposited in the Great Plain of North India in the form of fertile soil, making the plain one of the most fertile lands of the world. It has been estimated that the Ganga and the Indus carry 19 and 10 lakh tonnes of silt, per day respectively and the silt carried by the Brahmaputra is even more. It is, therefore, often said that the great plain of north India is a Gift of the Himalayas.
- Hydroelectricity: The Himalayan region offers several sites which can be used for producing hydroelectricity. There are natural waterfalls at certain places while dams can be constructed across rivers at some other places. The vast power potential of the Himalayan Rivers still awaits proper utilisation.
- Forest Wealth: The Himalayan ranges are very rich in forest resources. In their altitude, the Himalayan ranges show a succession of vegetal cover from the tropical to the Alpine. The Himalayan forests provide fuel wood and a large variety of raw materials for forest-based industries. Besides, many medicinal plants grow in the Himalayan region. Several patches are covered with grass offering rich pastures for grazing animals.
- Agriculture: The Himalayas do not offer extensive flatlands for agriculture but some of the slopes are terraced for cultivation. Rice is the main crop on the terraced slopes. The other crops are wheat, maize, potatoes, tobacco and ginger. Tea is a unique crop which can be grown on the hill slopes only. A wide variety of fruits such as apples, pears, grapes, mulberry, walnut, cherries, peaches, apricot, etc. are also grown in the Himalayan region.
- Tourism: By virtue of their scenic beauty and healthy environment, the Himalayan ranges have developed a large number of tourist spots. The hilly areas in the Himalayas offer cool and comfortable climate when the neighbouring plains are reeling under the scorching heat of the summer season. Millions of tourists from different parts of the country as well as from abroad throng the Himalayan tourist centres to enjoy their natural beauty and to escape from the summer heat of the plains. The increasing popularity of winter sports and the craze to enjoy snowfall has increased the rush of tourists in winters also. Srinagar, Dalhousie, Dharamshala, Chamba, Shimla, Kulu, Manali, Mussoorie, Nainital, Ranikhet, Almora, Darjeeling, Mirik, Gangtok, etc. are important tourist centres in the Himalayas.
- Pilgrimage: Apart from places of tourist’s interest, the Himalayas are proud of being studded with sanctified shrines which are considered to be the abodes of the Gods. Large number of pilgrim’s trek through difficult terrain to pay their reverence to these sacred shrines. Kailas, Amarnath, Badrinath, Kedarnath, Vaishnu Devi, Jwalaji, Uttarkashi, Gangotri, Yamunotri, etc. are important places of pilgrimage.
- Minerals: The Himalayan region contains many valuable minerals. There are vast potentialities of mineral oil in the tertiary rocks. Coal is found in Kashmir. Copper, lead, zinc, nickel, cobalt, antimony, tungsten, gold, silver, limestone, semi-precious and precious stones, gypsum and magnesite are known to occur at more than 100 localities in the Himalayas. Unfortunately, many of the mineral resources cannot be exploited at the present level of technological advancement due to adverse geographical conditions. Further advancements in modern technology may help in exploiting these resources. So, the future possibilities of mineral exploitation in the Himalayas are great.
The Northern Plains
- The northern plains are formed by the alluvial deposits brought by the rivers – the Indus, the Ganga and the Brahmaputra. These plains extend approximately 3,200 km from the east to the west. The average width of these plains varies between 150-300 km. The maximum depth of alluvium deposits varies between 1,000-2,000 m.
- The Northern Plain is broadly divided into three sections. The Western part of the Northern Plain is referred to as the Punjab Plains. Formed by the Indus and its tributaries, the larger part of this plain lies in Pakistan. Extends from Punjab in the West to Yamuna river in the East. The Indus and its tributaries–the Jhelum, the Chenab, the Ravi, the Beas and the Satluj originate in the Himalaya. This section of the plain is dominated by the doabs. They are composed by Bets (Khadar plains) and Dhaya (heavily gullied bluffs). With a distance of 640km from north-east to south-west and 300km from west to east, these flat plains occupy 1.75 lakh sq.km. They comprise Bist Doab (between Sutlej and Beas river), the Bari doab (between Beas and Ravi rivers), the Chaj Doab (between Chenab and Jhelum) and Sindh Sagar Doab (between Jhelum –Chenab and Indus rivers).
- The Ganga plain extends between Ghaggar and Teesta rivers. It is spread over the states of North India, Haryana, Delhi, U.P., Bihar, partly Jharkhand and West Bengal to its East, particularly in Assam lies the Brahmaputra plain.
- According to the variations in relief features, the Northern plains can be divided into three regions. From the north to the south, these can be divided into three major zones: the Bhabar, the Tarai and the alluvial plains. The alluvial plains can be further divided into the Khadar and the Bhangar.
- Bhabar is a narrow belt ranging between 8-10 km parallel to the Shivalik foothills at the break-up of the slope. As a result of this, the streams and rivers coming from the mountains deposit heavy materials of rocks and boulders, and at times, disappear in this zone.
- South of the Bhabaris the Tarai belt, with an approximate width of 10-20 km where most of the streams and rivers re-emerge without having any properly demarcated channel, thereby creating marshy and swampy conditions known as the Tarai. This has a luxurious growth of natural vegetation and houses a varied wildlife.
- The south of Taraiis a belt consisting of old and new alluvial deposits known as the Bhangar and Khadar respectively. These plains have characteristic features of mature stage of fluvial erosional and depositional landforms such as sand bars, meanders, oxbow lakes and braided channels.
- The Brahmaputra plains are known for their riverine islands and sandbars. Most of these areas are subjected to periodic floods and shifting river courses forming braided streams. The mouths of these mighty rivers also form some of the largest deltas of the world, for example, the famous Sunderbans delta. Otherwise, this is a featureless plain with a general elevation of 50-150 m above the mean sea level.
- The states of Haryana and Delhi form a water divide between the Indus and the Ganga river systems. As opposed to this, the Brahmaputra river flows from the northeast to the southwest direction before it takes an almost 90° southward turn at Dhubri before it enters into Bangladesh.
- These river valley plains have a fertile alluvial soil cover which supports a variety of crops like wheat, rice, sugarcane and jute, and hence, supports a large population.
The Peninsular Plateau
- Rising from the height of 150 m above the river plains up to an elevation of 600-900 m is the irregular triangle known as the Peninsular plateau.
- Delhi ridge in the northwest, (extension of Aravalis), the Rajmahal hills in the east, Gir range in the west and the Cardamom hills in the south constitute the outer extent of the Peninsular plateau. However, an extension of this is also seen in the northeast, in the form of Shillong and Karbi-Anglong plateau.
- The Peninsular India is made up of a series of patland plateaus such as the Hazaribagh plateau, the Palamu plateau, the Ranchi plateau, the Malwa plateau, the Coimbatore plateau and the Karnataka plateau, etc. This is one of the oldest and the most stable landmass of India. The general elevation of the plateau is from the west to the east, which is also proved by the pattern of the flow of rivers. Name some rivers of the Peninsular plateau which have their confluence in the Bay of Bengal and the Arabian sea and mention some landforms which are typical to the east flowing rivers but are absent in the west flowing rivers.
- Some of the important physiographic features of this region are tors, block mountains, rift valleys, spurs, bare rocky structures, series of hummocky hills and wall-like quartzite dykes offering natural sites for water storage. The western and northwestern part of the plateau has an empathic presence of black soil.
- This Peninsular plateau has undergone recurrent phases of upliftment and submergence accompanied by crustal faulting and fractures. (The Bhima fault needs special mention, because of its recurrent seismic activities). These spatial variations have brought in elements of diversity in the relief of the Peninsular plateau. The northwestern part of the plateau has a complex relief of ravines and gorges. The ravines of Chambal, Bhind and Morena are some of the well-known examples.
- On the basis of the prominent relief features, the Peninsular plateau can be divided into three broad groups:
- The Deccan Plateau
- The Central Highlands
- The Northeastern Plateau.
The Deccan Plateau
- This is bordered by the Western Ghats in the west, Eastern Ghats in the east and the Satpura, Maikal range and Mahadeo hills in the north.
- Western Ghats are locally known by different names such as:
- Sahyadri in Maharashtra,
- Nilgiri hills in Karnataka and Tamil Nadu and
- Anaimalai hills and Cardamom hills in Kerala.
- Western Ghats are comparatively higher in elevation and more continuous than the Eastern Ghats. Their average elevation is about 1,500 m with the height increasing from north to south. ‘Anaimudi’ (2,695 m), the highest peak of Peninsular plateau is located on the Anaimalai hills of the Western Ghats followed by Dodabetta (2,637 m) on the Nilgiri hills.
- Most of the Peninsular rivers have their origin in the Western Ghats.
- Eastern Ghats comprising the discontinuous and low hills are highly eroded by the rivers such as the Mahanadi, the Godavari, the Krishna, the Kaveri, etc.
- Some of the important ranges include the Javadi hills, the Palconda range, the Nallamala hills, the Mahendragiri hills, etc. The Eastern and the Western Ghats meet each other at the Nilgiri hills.
The Central Highlands
- They are bounded to the west by the Aravali range. The Satpura range is formed by a series of scarped plateaus on the south, generally at an elevation varying between 600-900 m above the mean sea level. This forms the northernmost boundary of the Deccan plateau. It is a classic example of the relict mountains which are highly denuded and form discontinuous ranges.
- The extension of the Peninsular plateau can be seen as far as Jaisalmer in the West, where it has been covered by the longitudinal sand ridges and crescent-shaped sand dunes called barchans.
- This region has undergone metamorphic processes in its geological history, which can be corroborated by the presence of metamorphic rocks such as marble, slate, gneiss, etc.
- The general elevation of the Central Highlands ranges between 700-1,000 m above the mean sea level and it slopes towards the north and northeastern directions.
- Most of the tributaries of the river Yamuna have their origin in the Vindhyan and Kaimur ranges. Banas is the only significant tributary of the river Chambal that originates from the Aravalli in the west.
- An eastern extension of the Central Highland is formed by the Rajmahal hills, to the south of which lies a large reserve of mineral resources in the Chotanagpur plateau.
The Northeastern Plateau
- It is an extension of the main Peninsular plateau. It is believed that due to the force exerted by the northeastward movement of the Indian plate at the time of the Himalayan origin, a huge fault was created between the Rajmahal hills and the Meghalaya plateau.
- Later, this depression got filled up by the deposition activity of the numerous rivers. Today, the Meghalaya and Karbi Anglong plateau stand detached from the main Peninsular Block. The Meghalaya plateau is further subdivided into three:
- The Garo Hills;
- The Khasi Hills;
- The Jaintia Hills, named after the tribal groups inhabiting this region.
- An extension of this is also seen in the Karbi Anglong hills of Assam. Similar to the Chotanagpur plateau, the Meghalaya plateau is also rich in mineral resources like coal, iron ore, sillimanite, limestone and uranium.
- This area receives maximum rainfall from the south west monsoon. As a result, the Meghalaya plateau has a highly eroded surface. Cherrapunji displays a bare rocky surface devoid of any permanent vegetation cover.
The Indian Desert
- To the northwest of the Aravali hills lies the Great Indian desert.
- It is a land of undulating topography dotted with longitudinal dunes and barchans.
- This region receives low rainfall below 150 mm per year; hence, it has an arid climate with low vegetation cover. It is because of these characteristic features that this is also known as Marusthali.
- It is believed that during the Mesozoic era, this region was under the sea. This can be corroborated by the evidence available at wood fossils park at Aakal and marine deposits around Brahmsar, near Jaisalmer (The approximate age of the wood fossils is estimated to be 180 million years).
- Though the underlying rock structure of the desert is an extension of the Peninsular plateau, yet, due to extreme arid conditions, its surface features have been carved by physical weathering and wind actions. Some of the well pronounced desert land features present here are mushroom rocks, shifting dunes and oasis (mostly in its southern part).
- On the basis of the orientation, the desert can be divided into two parts: the northern part is sloping towards Sindh and the southern towards the Rann of Kachchh.
- Most of the rivers in this region are ephemeral. The Luni river flowing in the southern part of the desert is of some significance.
- Low precipitation and high evaporation make it a water deficit region. There are some streams which disappear after flowing for some distance and present a typical case of inland drainage by joining a lake or playa. The lakes and the playas have brackish water which is the main source of obtaining salt.
The Coastal Plains
- On the basis of the location and active geomorphological processes, it can be broadly divided into two:
- the western coastal plains;
- the eastern coastal plains.
- The western coastal plains are an example of submerged coastal plains. Because of this submergence it is a narrow belt and provides natural conditions for the development of ports and harbours. Kandla, Mazagaon, JLN port Navha Sheva, Marmagao, Mangalore, Cochin, etc. are some of the important natural ports located along the west coast.
- Extending from the Gujarat coast in the north to the Kerala coast in the south, the western coast may be divided into following divisions:
- Kachchh and Kathiawar coast in Gujarat,
- Konkan coast in Maharashtra,
- Goan coast in Karnataka and
- Malabar coast in Kerala
- The western coastal plains are narrow in the middle and get broader towards north and south. The rivers flowing through this coastal plain do not form any delta. The Malabar coast has got certain distinguishing features in the form of ‘Kayals’ (backwaters), which are used for fishing, inland navigation and also due to its special attraction for tourists. Every year the famous Nehru Trophy Vallamkali (boat race) is held in Punnamada Kayal in Kerala.
- As compared to the western coastal plain, the eastern coastal plain is broader and is an example of an emergent coast. There are well developed deltas here, formed by the rivers flowing eastward into the Bay of Bengal. These include the deltas of the Mahanadi, the Godavari, the Krishna and the Kaveri.
- Because of its emergent nature, it has a smaller number of ports and harbours. The continental shelf extends up to 500 km into the sea, which makes it difficult for the development of good ports and harbours. Name some ports on the eastern coast.
|Difference between West and East Coastal Plains|
|West Coastal Plains||East Coastal Plains|
|1. Located between the Western Ghats and the Arabian Sea coast||1. Located between the Eastern Ghats and the Bay of Bengal coast|
|2. A narrow plain with an average width of 64km.||2. Comparatively a broader plain with an average width of 80-100km|
|3. Drained by short and swift streams which are unable to form deltas.||3. Drained by big rivers like Mahanadi, Godavari, Krishna and Kavery that have formed large deltas|
|4. Several Lagoon||4. Comparatively less|
|5. Have indented coast which supports many ports||5. Have more or less s straight coast where good ports are lacking|
- There are two major island groups in India:
- one in the Bay of Bengal and
- the other in the Arabian Sea.
- The Bay of Bengal island groups consist of about 572 islands/islets. These are situated roughly between 6°N-14°N and 92°E -94°E. The two principal groups of islets include the Ritchie’s archipelago and the Labyrinth island. The entire group of islands is divided into two broad categories – the Andaman in the north and the Nicobar in the south. They are separated by a water body which is called the Ten-degree channel. It is believed that these islands are an elevated portion of submarine mountains. However, some smaller islands are volcanic in origin. Barren island, the only active volcano in India is also situated in the Nicobar Islands. The coastal line has some coral deposits, and beautiful beaches. These islands receive conventional rainfall and have an equatorial type of vegetation.
- The islands of the Arabian sea include Lakshadweep and Minicoy. These are scattered between 8°N-12°N and 71°E -74°E longitude. These islands are located at a distance of 280 km-480 km off the Kerala coast. The entire island group is built of coral deposits. There are approximately 36 islands of which 11 are inhabited. Minicoy is the largest island with an area of 453 sq. km. The entire group of islands is broadly divided by the Eleventh-degree channel, north of which is the Amini Island and to the south of the Cannanore Island. The Islands of this archipelago have storm beaches consisting of unconsolidated pebbles, shingles, cobbles and boulders on the eastern seaboard.
- Contemporary India-I by NCERT
- India: Physical Environment by NCERT
- India Year Book