They are 240 to 500 kms. Broad (as in Kashmir) and cover about 500,000 sq. kms. Their areal stretch is between the Indus river and the Brahmaputra, encompassing parts of the Himachal Pradesh, the entire Jammu and Kashmir, the Dehradun district and Kumaon district of Uttarakhand, Nepal, Sikkim and Bhutan; the Darjeeling district of West Bengal; the states of Assam, Manipur, Tripura, Nagaland, Meghalaya, Arunachal Pradesh and Mizoram.
The Himalayas mountains are young weak and flexible in their geological structure unlike the rigid and Peninsular block. Consequently, they are still subjected to the interplay of exogenic and endogenic forces, resulting in the development of faults, folds, and thurst plains.
These mountains are typically tectonic in origin, having been uplifted during the tertiary times from the bed of the great Midland sea of Tethys, lying between the two ancient landmasses of Angaraland in the north and Gondwana land in the south.
They took about 7 million years to attain their present height. The shape of the Himalayas is like an arc. This may probably be due to the maximum push offered by the Aravallis in the north-west and the Assam ranges in the north-east, when the peninsula drifted towards the north.
Both these ranges too extended arms pushing out to the extremes while the central area sagged in a crescent form. Thus, Himalayan chain got an arcuate trend with the convex side towards the Ganges plain.
The heights of the Himalayas are covered with perpetual snow which feed the valley glaciers. The main crust of the Himalayan ranges rises above the snow-line which varies between 4,500 to 6,000 metres in the west and 4,000 to 5,800 metres in the east. Towards the Far East, the eastern ranges (Khasi, Jaintia, and Naga Hills) are not so high. The Himalayas are not a single, continuous chain of mountains but a series of parallel or converging ranges.
They are intersected by numerous valleys, like that of the Kashmir Valley and the Karewas, the Doon valley (Uttarakhand), the Kangra and Kulu valley (Himachal Pradesh), Kathmandu (in Nepal), Bhagirathi valley (near Gangotri) and Mandakini valley (near Kedarnath). These are fertile and are of great scenic beauty. Extensive plateaus like Ladakh, Cherrapunji and Shillong plateau occur in the Himalayas.
Classification of the Himalayas:
The Himalayas may be studied both breadth wise (i.e. longitudinally) and region-wise.
(A) Longitudinal Section of the Himalayas:
Breadth-wise the Himalayas can be classified into four parts:
(i) The Trans-Himalayas,
(ii) The Greater Himalayas,
(iii) The Lesser Himalayas, and
(iv) The Outer Himalayas.
(i) The Trans-Himalayas or the Tibetan-Himalayas:
This range comprises Karakoram and the Kailash which overlook the sacred Mansarovar Lake. The average width of this region is 40 kms at the eastern and western extremities and 222 kms. In the central part. It is a region of lofty peaks and vast glaciers.
K2 is the highest peak (8,611m). Other important peaks are Gasherbrum I (K5 (8,080 m), Broad Peak (8,047m), Gasherbrum II (8,035 m), Rakaposhi (7,788 m) and Haramosh (7,397m). The largest glaciers are the Hispar and Batura (over 57 km, long) and Biafo and Baltoro (60 km. long).
(ii) The Greater Himalayas:
Also known as the Himadri, Inner or the Central Himalaya, comprise the northern -most ranges rising to an average height of about 6,000 metres with breadth ranging from 120 to 190 kms. The core of these mountains is composed of the Archaean rocks like granite, gneisses and the schists of unknown geological ages. In the alpine zone (4,800 metres and above), rhododendrons trees with crooked and twisted stems, thick shrubs with a variety of beautiful flowers and grass grow.
Some of the highest peaks are situated in this range such as the Mt. Everest (8,848m), (Kanchanjunga (8,598m), Dhaulagiri (8172 m) Nanda Devi (7,817m), Nangaparbat (8,126m), Makalu (8,481m), Manasalu (8,156m), and a host of others. Few passes occur in these ranges though at very high elevation (over 4,500m). They are Sara Lapcha La and Shipki La (in Himachal Pradesh), Thaga La, Niti and Lipu Lekh (in Uttarakhand), Nathula and Jelep La (in Sikkim); and Burzil, Jojila (in Kashmir) and Bomdila (Arunachal Pradesh) etc.
(iii) The Lesser or the Middle Himalayas:
They have an average elevation of about 3,500 to 5,000 metres with an average width of 60 to 80 kms. These consist of the southern spurs’ of Great Himalayas and run parallel to it, extending as far as the outer Shivaliks.
Important ranges included are the Dhauladhar, the Pirpanjal, Nag Tiba, Mahabharat Range and Mussoorie Range. These are also snow-capped and majestic but more friendly to human contacts and less inaccessible to pilgrims, explorers, and saints. Famous hill resorts like Shimla, Chail, Ranikhet, Chakrata, Mussoorie, Nainital, Almora, Darjeeling all lie in them.
They are composed of metamorphic rocks and unfossiliferous sedimentary rocks from Algonkian or Pre-Cambrian to Eocene in age. It differs from Himadri in its more regular and lower elevations. The southern slopes are bare and rugged while the northern ones have thick vegetation. The zone between 1,500 and 2,400 metres is covered by evergreen and oak forests and that between 2,400 and 3,000 metres by coniferous forests.
(iv) The Outer Himalayas or the Shivaliks:
They consist of the foot-hills which run almost from Potwar plateau to the Brahmaputra valley. They are 1,000 to 1,500 metres high with a width ranging from 15 to 50 kms. It is a chain of low-lying hills, entirely made of fluvial deposits like sand, clay and rounded stones, slates, etc.
The region is mostly ill-drained (like that of Tarai), but cool and finely wooded, extending a friendly welcome to human effort and habitation. Valleys in these ranges are known as Doons like Dehradun valley, dhampur and Kotli valleys in Jammu and Kota, Patli and Chaukhamba valley in Uttar Pradesh. Doons are characterized by fault scraps, anticlinal valleys and synclinal ranges.
(B) Transverse or Regional Divisions of Himalayas:
Apart from these longitudinal sub-divisions, the Himalaya exhibit regional characteristics and as such, the following regions have been identified:-
(i) The Kashmir or North-Western Himalayas:
Mostly lies in Jammu and Kashmir covering an area of 3, 50,000 sq. kms. They are about 700 kms. Long and 500 kms. Wide, with an average elevation of 3,000 metres. They have the largest share of snows and glaciers. In the Pirpanjal range exist two passes, Pirpanjal and Banihal. It is breached by the Kishanganga, the Jhelum and the Chenab. Vale of Kashmir lies in this region.
(ii) The Punjab Himalayas:
It stretches north-westwards from the Sutlej for about 570 km. and covers an area of 45,000 sq. km. The northern slopes of this range are bare and rugged and enclose plateau with lakes (Mansarovar Rakas Tal, etc). The southern slopes are covered with forest and do not enclose any high plains. Zojila, Rohtang and Bara Lapcha are important passes. It is in this section that Kangra Lahul and Spiti valleys are situated.
(iii) The Kumaon Himalayas:
It extends from the river Sutlej to the Kali to a distance of about 320 kms. It covers about 38,000 sqs. Km. The highest peak is Nanda Devi followed by others like Kamet, Badrinath, Kedarnath, Nandakot, Gangotri and others. The region is said to have about 360 lakes, some of which have now been completely or partially desiccated but remnants of these still remain in the form of Nainital and Bhimtal lakes.
This section of the Himalaya has great significance for the Hindus due to the Bhagirathi, the Ganga and Jamuna, which have their sources in the zone. Badrinath, Kedarnath, Gangotri, and Jamunotri as household words all over India for their sanctity, antiquity and ancient religious glory.
(iv) The Nepal Himalayas:
These Himalayas are situated between the Kosi valley on the west and the Tista Valley on the east. It is called Sikkim Himalayas in Sikkim and Darjeeling Himalaya in West Bengal and Bhutan Himalaya in Bhutan. It is the longest Himalayan region. It is 800 km long and is the highest Himalayan region. Its peaks are Mt. Everest, Kanchanjunga, Dhaulagiri, Kakalu and Anapurna.
(v) The Central Himalayas:
It stretches from river Kali to river Tista for about 800 kms. Covering an area about 1, 16, 80 sq. kms. It has the distinction of carrying the highest peaks in the world, Dhaulagiri, Annapurna, Mansalu Gossainthan, Mt. Everest, Makalu and Kanchanjunga, etc. The range is known as the Sikkim Himalaya in Sikkim; Darjeeling Himalaya in West Bwngal; and Bhutan Himalaya in Bhuyan.
(vi) The Assam Himalayas:
It stretches from Tista the Brahmaputra to a distance of about 720 kms. It covers about 67,500 sq. kms. It rises over 800 m above the Brahmaputra Valley. The noted peaks are Pauhunri, and Kulbakangri.
The Naga Hills form the watershed between India and Myanmar (Burma). Saramati is its peak. The Kohima hills have Japuo peak. Manipur Hills encircle the Cachar plain North Cachar hills are over 500 to 1,000 metres high. Mizo hills are the southern part of the north-eastern ranges. Garo hills cover about 8,180 sq. kms. Khasi, Jaintia and Mikir, Aka Dafla Miri, and Abor are other hills in which live the aboriginals of the same name.
Eastern and Western Himalayas Compared:
In the northwest, the Himalayan ranges coalesce with the diversely arranged mountain chains of the Karakoram, the Hindu Kush, Kun Lun, Tien Shah, Pamir, Alay and the Trans Alay Ranges which converge on the central promontory of Pamir.
The eastern Himalayas rise rather abruptly from the plains of Bihar and Bengal with the highest peaks of Everest and Kanchenjunga located quite close together. In contrast, the Western Himalayas attain height through a graded series of low ranges.
Here the first stage is set by the sub-Himalayan hills of Jammu and Kashmir, the second by the lesser Himalayan ranges of Pir Panjal and the Dhauladhar and the third by the Great Himalayan, North Kashmir and the Zaskar Ranges. Further northward they are replaced by the Ladakh-Kailash and the Karakoram Ranges.
The four-fold geological division of the Himalayas based on the age of rock formations and their type are:
(i) The Tibetan zone, composed of fossil-bearing sedimentary rocks ranging from Palaeozic to Eocene of the Pleistocene era, lies to the north of the Great Himalayas,
(ii) The central or the Himalayan zone is mainly composed of crystalline and metamorphic rocks,
(iii) The Himalayan Nappe Zone consist of overfolds and thrust faults of a more complex type where large bodies of older rocks have been physically displaced and thrust on the newer ones along the recumbent folds over large areas,
(iv) The outer or the sub-Himalayan zones, corresponding to the Shivaliks, is composed to the sedimentary deposits belonging to upper Tertiary and believed to have been derived from the crowded materials of the main Himalayan ranges themselves.
Passes Through the Mountain Wall:
Though the mountain wall constitutes a formidable physical barrier between the Sub-continent and the rest of Asia, there are some very important passes. These are (from north to south): the Khyber Pass, the Kurram Pass, the Tochi pass, the Gomal Pass and the Bolan Pass.
(i) The Khybar Pass (1,000 m) is the most famous of all. It leads from Peshawar to Kabul. Most of the invaders in the past came through this opening in the Northern Mountain Wall.
(ii) The Gomal Pass: (1,525 m) south of the Khyber Pass there is the Gomal Pass. This pass served as a trade route passing through the districts Wazirstan (now in Pakistan).
(iii) The Bolan Pass: (1,800 m) lies between the Sulaiman and the Kirthar Ranges. It leads from Kandhar to Quetta.
(iv) In the very north are two difficult routes via the Karakoram Pass and the Zozila Pass where there are roads communicating with Srinagar.
(v) The Shipki Pass leads from Punjab to Tibet.
(vi) Bomdila pass: is in Arunachal Pradesh in India.