Himalayas are the loftiest mountain ranges of the world, which emerged as a cumulative product of various fold mountain orogenies that started around 100 million years (my) ago when Indian peninsula separated from Africa & moved northward to collide with Asian plate.
As both the plates were Continental Plates, neither of two subducted under the other. The continental crust was buckled, fractured and shortened.
Prior to collision, both the landmasses were separated by an ocean basin.
Convergence of these two led to an ocean-ocean interaction wherein the oceanic edge of peninsular plate got subducted under the oceanic edge of Asian Plate.
Partial melting of subducting ocean plate resulted in an andesitic volcanic arc known as Drass Island Arc.
Erosion of newly formed arc discharged large quantities of sediments to already sediment laden continental margins.
When continental plates collided, squeezing, folding and deforming of sediments took place.
The anticlockwise rotation (door slamming shut movement) of peninsula closed the Tethys Sea, existing between the two, and led to the rise of its sediments.
The Himalayan Range with deformed sedimentary rocks and fragments of volcanic arc was thus formed.
The spreading centre propelling India northward is still active. This is the reason for the on-going growth of Himalayas @ few cm/year.
Evidence: severe earthquakes as north as China and Mongolia.
SALIENT FEATURES OF STRUCTURE OF HIMALAYAS
Stepped Rise: The door slamming shut movement resulted in younger age & greater heights of Eastern Himalayas.
Further, the consequent gradual release of pressure on western side caused stepped rise of Himalayas as compared to their abrupt rise on Eastern side.
Syntaxial Bending: The forceful intrusion of peninsula & consequent compression created syntaxial bending concaving southwards with transform faults along edges.
Parallel Ranges: An important feature of Himalayas is the existence of parallel ranges interspersed by faults.
Tethys Himalayas in the north paralleled by Inner, Middle & Outer Himalayas southward.
Tethys or Tibetan Himalayas are composed of fossilifereous sedimentary rocks of marine origin with altitudes of 3000-4300 m & 40 km width.
The Inner or Greater Himalayas also called Himadaris form world‘s highest Mountain Ranges with average height of 6000m and 50km width.
These are composed of crystalline & metamorphic rocks like granites, gneiss and schiests.
The Middle Himalayas are characterized by highly complicated & strongly folded & faulted belt of allochthonous rocks with elevations of 3600-4200m & width of 60 - 80km.
It is a belt of thrust sheets & nappes.
The Shiwaliks are exclusively tertiary formations with a Series of anticlines and synclines.
Fault Zones: The compressional forces strained the rocks & crack zones developed.
ITSZ (Indus Tsangpo Suture Zone) is the zone along which the two continental plates interact.
It consists of metamorphosed rocks.
MCT (Main Central Thrust) is a reverse fault with Orthoclinal Structures (90°), consisting of extremely crushed gneiss, Schiest etc.
MBF (Main Boundary Fault) is a reverse fault continuous throughout the Himalayas.
The HFF (Himalayan Front Fault) represents the present belt of crustal deformation.
MAJOR DIVISIONS OF THE HIMALAYAS
Geographically the entire Himalayan region can be divided into:
1 The Himalayas
2 The Trans-Himalayas
3 The Eastern Hills
THE HIMALAYAS
The Himalayas are not a single chain or range of mountains, but a series of several more or less parallel or converging ranges.
These ranges are separated by deep valleys.
A succession of at least 3 parallel ranges from the Indo-Gangetic plain to be the Tibet Plateau may be recognised in the Himalayas.
1 The Shiwalik Range: the Shiwalik comprises the outermost range of the Himalayas.
This chain of hills runs almost parallel to the lesser Himalayas for a distance of about 2400 km from the Potwar Plateau to the Brahmaputra valley.
The width of the Shiwalik varies from 50 km in Himachal Pradesh to less than 15 km in Arunachal Pradesh.
Shiwalik are formed of great thickness of Mio-Pleistocene sands, gravels and conglomerates which have been brought by the rivers flowing from the higher ranges of the Himalaya.
The eastern part of the Shiwalik range up to Nepal is covered with thick forests but the forest cover becomes thin in the west.
2 The Middle or the Lesser Himalayas:
In between the Shiwaliks in the south and the Great Himalayas in the north is the Middle Himalaya running almost parallel to both the ranges.
It has an intricate system of ranges which are 60-80 km wide having elevations varying from 3500 to 4500 m above sea level.
The important ranges included are the Pir Panjal, the Dhola Dhar, the Mussorie Range, the Nag Tiba and the Mahabharata Lekh.
The best known passes are the Pir Panjal Pass, the Bidil, Golabghar Pass and Banihal Pass.
Between the Pir Panjal and the Zaskar Range of the main Himalayas, lies the famous valley of Kashmir.
Further east, the Middle Himalayas are marked by the Mussorie and the Nag Tiba ranges.
Majority of the Himalayan hill resorts like Shimla, Mussorie, Ranikhet, Nainital, Almora and Darjeeling, etc, are located here.
3 The Great Himalayas:
This is northernmost or the innermost of all the Himalayan ranges.
With an average elevation of 6100 m above sea level and an average width of about 25 km, this is the loftiest and the most continuous mountain range of the world.
It is mainly formed of the central crystalline (granites and gneisses) overlain by metamorphosed sediments.
The folds in this range are asymmetrical with steep south slope and gentle North Slope.
This mountain range boasts of the tallest peaks of the world.
There are several peaks over 8000 m in altitude.
They are Mount Everest, Kanchenjunga-I, Dhaulagiri, Nanga Parbat, Annapurna, Nanda Devi, Kamet, Namcha Barwa, Badrinath.
Many important passes pierce through the Great Himalaya namely,
The Burzil pass and the Zoji La in Jammu
and Kashmir,
the Bara Lacha La and the Shipki La in Himachal Pradesh,
the Thaga La, the Niti Pass and the Lipu Lekh pass in Uttar Pradesh and
the Nathu La and the Jelep La in Sikkim.
THE TRANS HIMALAYAS/ TIBETAN HIMALAYAS
The Himalayan ranges immediately north of the Great Himalayan range are called the Trans-Himalayas.
These are also called the Tibetan Himalayas because most of it lies in Tibet.
The Zaskar, the Ladakh, the Kailas and the Karakoram are the main ranges of the Trans–Himalayan system.
It stretches for a distance of about 1000 km in east west direction and its average elevation is 3000 m above mean sea level.
The Zaskar Range branches off from the great Himalayan Range near 80o E longitude and runs more or less parallel to it.
North of the Zaskar Range and running parallel to it is the Ladakh Range.
The Kailas Range (Gangdise in Chinese) in western Tibet is an offshoot of the Ladakh range.
The highest peak is Mount Kailas (6714 m).
The northern most range of the Trans Himalayan Ranges in India is the Great Karakoram Range.
It forms India‘s frontier with Afghanistan and China.
The Ladakh Plateau lies to the north-east of the Karakoram Ranges.
EASTERN HILLS OR THE PURVANCHAL
The ruggedness is more than other parts among these hills with the extreme of it in Arunachal Pradesh.
This region is dominated by many small hills like Dafla, Miri, Abor, Mishmi, Patkai Bhum, Naga etc.
It is characterized by high degree of soil erosion, due to deforestation.
After crossing the Dihang gorge, the Himalayas take a sudden southward turn and form a series comparatively low hills running in the shape of a crescent with its convex side pointing towards the west.
These hills are collectively called the Purvanchal because they are located in the eastern part of India.
In the north is Patkai Bum which forms the international boundary between Arunachal Pradesh & Myanmar.
After running for some distance southwards, it merges into Naga Hills where Saramati (3826 m) is the highest peak Patkai Bum and Naga Hills from the watershed between India and Myanmar.
The Kohima hills to west are made up of sandstone and slate and have a very rough topography.
The Brail range separates Naga Hills from Manipur Hills.
Jaintia, Khasi and Garo Hills are eastward continuation of the Indian peninsular block and have been separated by the Bengal Basin.
South of the Manipur Hills are the Mizo Hills.
The highest point is the Blue Mountain (2157 m) in the south.
Lohit, Dihang & Dibang are the important rivers of this region.
Namcha Barwa is the place where Brahmaputra takes a southward turn to enter into India.
Bomdila is an important Pass over here facilitating the movement across the ranges.
RELIEF OF HIMALAYAS
An array of geomorphic process have moulded & chiseled the landscape, over space & time, thereby generating amazing assemblage of land forms over Himalayas.
Salient features of Himalayan relief are:
Broader in Western Parts: Himalayas are broader in western parts while their width narrows down in the eastern part.
In the E. Part, distinction between parallel ranges is generally lost.
Further, Inner Himalayas & Shiwaliks are continuous throughout the longitudinal distance from west to east, while Middle Himalayas are broken into hills- parallels & oblique.
Most of the Hill Stations like Mussorie, Shimla, Dehradun etc. lie over Middle Himalayas.
1. Kashmir Range a. Ratan Pir Range
2. Pir Panjal b. Mussouri Range
3. Dhola Dhar c. Mahabharata
4. Nag Tiba
Antecedent Rivers: in the geological past, when Himalayas were rising, the rivers kept on eroding them at the places of their flow, thereby creating deep gorges as in Indus, Satluj & others.
Such a pattern makes the rivers antecedent.
a. Between Indus and Sutlaj :Kashmir Himalayas
b. Between Sutlaj and Kali :Himachal in west + Kumaon in East
c. Between Kali and Tista :Nepal Himalayas
d. Between Tista and Brahmaputra :Assam Himalayas
e. Kashmir + Himachal Himalayas make Punjab Himalayas
CLASSIFICATION OF HIMALAYAS ON THE BASIS OF GEOGRAPHICAL LOCATION
KASHMIR HIMALAYAS
These ranges have a rugged mountainous topography with several parallel snow covered ranges.
Between Pir Panjal & Zaskar ranges lies the Kashmir valley with alluvial deposits.
Kashmir valley is of tectonic origin.
Pir Panjal & Dhaola Dhar Ranges belong to Middle Himalayas.
A special feature here is tilted beds of lake deposits on Pir Panjal Range called Karewas.
K2 (8611 m) and Gasherbrum on Karakoram Range and Nanga Parbat (8126 m) are important peaks.
1. Karakoram a. Pir Panjal Pass
2. Ladakh b. Bara Lacha La
3. Zaskar c. Banihal
4. Pir Panjal
5. Dhaula Dhar
Several passes like Pir Panjal, Banihal, Burzil, Baralacha La, Zoji La etc.
have made the connectivity possible.
Important Lakes of the region are Wular & Dal on Jhelum, Tso Morari & Pangong.
World‘s highest battlefield – Siachen – lies over Karakoram Range.
KUMAON HIMALAYAS
These lie between the Sutlej and the Kali Rivers on the eastern side of Himachal Himalayas.
Its western part is called Garhwal Himalaya while the eastern part is known as Kumaon Himalaya proper.
The Shiwaliks & Inner Himalayas continue over here with Middle Himalayan ranges of Mussorie and NAG Tiba Ranges.
Between Shiwaliks & Middle Himalayas lie narrow longitudinal valleys called Dunes e.g.
Dehradun, Kothridun, Patlidun. Kedarnath, Nanda Devi, Badrinath, Kamet, Trisul and Gangotri are important Peaks.
The sources of sacred rivers like the Ganga and the Yamuna are located in the Kumaon Himalayas.
Nainital and Bhimtal are important lakes.
NEPAL HIMALAYAS
This section of the Himalayas stretches for a distance of 800 km between the Kali and the Tista rivers.
This is the tallest section of the Himalayas and is crowned by several peaks of perpetual snow.
Mount Everest is the tallest peak of the world.
The other major peaks are Kanchenjunga (8598 m), Dhaula Giri, and Annapurna.
ASSAM HIMALAYAS
The Himalayan ranges from Tista to Brahmaputra Rivers covering a distance of 750 km are called the Assam Himalayas.
This part of the Himalayas spreads over large parts of Sikkim, Assam and Arunachal Pradesh and has elevation much less than that of the Nepal Himalayas.
The important peaks of this region are Namcha Barwa (7756 m), Kula Kangri (7539 m) and Chomo Lhari (7327 m)
SIGNIFICANCE OF HIMALAYAS
The Himalayas comprises the most dominating geographical feature on the surface of earth.
They are the body and soul of India.
The following few points will bring out the significance of Himalayan Mountains to India.
1 Himalayas have provided a sub-continental character to the country, both physically and culturally.
Physically, it demarcates India vis-à-vis climate, land frontiers, rivers etc.
Culturally, it defines India in terms of demography, its culture, composition of people etc.
2 Climatic Influence: 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.
3 Defence. The Himalayas have been protecting India from outside invaders since the early times thus serving as a defence barrier.
It acts as a buffer between Indian subcontinent & other Asian Countries especially China.
4 Source of 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 feeding grounds of the mighty rivers of India.
Himalayan rivers are perennial and serve the agricultural needs of great Indian plains through a network of canals.
5 Fertile soils. The great rivers and their tributaries carry enormous amount of alluvium while descending from the Himalayas.
This is deposited in the Great Plains of North India in the form of fertile soils, making the plains one of the most fertile lands of the world.
6 Hydroelectricity. The Himalayan region offers several sites which can be used for producing hydroelectricity.
The vast power potential of the Himalayan Rivers still awaits proper execution.
Indian Himalayan Region (IHR), also known as the water tower of the world, hold potential of 1,48,700 MW of which we have been able to utilize, 22.4%.
National Electricity Policy reiterates that maximum emphasis would be laid on the development of the feasible hydro power potential in the country and majority of these projects are located in Himalayan region.
Bhakra, Nathpa-Jhakri, Uri, Chamera, Teesta etc. are the major projects here.
7 Forest Wealth. These ranges are very rich in forest resources and provide fuel wood and a large variety of raw materials for forest based industries.
Besides many medicinal plants grow in Himalayan regions.
They also offer rich pastures for grazing the animals.
8 Agriculture. Some of the slopes are terraced for cultivation.
Rice is the main crop on the terraced fields. Other crops are wheat, maize, potatoes, tobacco and ginger.
Tea is a unique crop which can be grown on the hill slopes only.
Fruits such as apples, pears, grapes, mulberry, walnut, cherries, peaches, apricot, etc. are also grown in the Himalayan regions.
Further the agriculture of great plains is the ultimate contribution of Himalayas.
9 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 and the craze to enjoy the snowfall have increased the rush of tourists in winters also.
Srinagar, Dalhousie, Dharamshala, Chamba, Shimla, Kulu, Manali, Mussoorie, Nanital, Ranikhet, Almora, Darjeeling, Mirik, Gangtok, etc. are important tourist centres in the Himalayas.
10 Pilgrimage: Himalayas are proud of being studded with sanctified shrines which are considered to be the abodes of the Gods.
Kailas, Amarnath, Badrinath, Kedarnath, Vaishnu Devi, Jwalaji, Uttarkashi, Gangotri, Yamunotri, etc, are important places of pilgrimage.
11 Minerals. 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.
12 The Passes in the rugged terrain acted as a gateway to foreign intruders during the past time.
Presently these play an important role in facilitating the movement of people through roads and the promotion of trade.
Some of these routes include: Zoji La, Banihal, Nathula and Jelepla Passes.
13 Many strategically important roads pass through these mountains and act as a lifeline to Indian security. Important ones include J&K 1A, 1B, 1C, 1D.
14 Himalayas are the house of many of the world‘s highest battlefields.
Since 1984, India and Pakistan have been locked in a bitter battle over the control of Siachen.
Karakoram highway linking the two countries, soon gave Siachen strategic importance.
15 Demarcating boundaries between countries: Himalayas and lower Himalayas form a boundary with countries like Myanmar, Bhutan, Nepal, China, Pakistan and Afghanistan.
Discussing the structure and relief of Himalayas takes us to logical conclusion that these are a prominent landmass over the surface of earth.
However, the urge for greater energy, developmental needs & unscientific ways have turned these delicately balanced ecosystems into “Ecological Hot-Spots”.
Through Deforestation, soil erosion and unsustainable mining activities, man has threatened his own existence on this earth.
There is still an opportunity with us to review & rethink of ―what‖ development and development ―for whom‖.
It could certainly be ―sustainable development for all‖. Choice is ours.
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