The Himalayas have also been divided by Sir Sidney Burrard into four transverse regions, viz., (1) die Punjab Himalaya (560 km long between die Indus and the Satluj rivers, (2) The Kumaun Himalaya (320 km long between die Satluj and the Kali rivers), (3) The Nepal Himalaya (800 km long between the Kali and the Tista rivers), and (4) The Assam Himalaya (720 km long between the Tista and the Brahmaputra rivers). Prof. S P. Chatterjee has divided the Himalayan region into 3 meso physiographic regions-(1) Western Himalaya (Kashimr, Punjab and Kumaun Himalayas), (2) Central Himalaya (Nepal Himalaya), and (3) Eastern Himalaya-besides the Purvanchal consisting of the nordi-eastem ranges (S .P. Chatterjee, 1964). R.L. Singh (1971) has made three fold subdivisions of die Himalayas-(i) Western Himalaya (1. Kashmir Himalaya and 2. Himachal Himalaya), (ii) Central Himalaya (3. U.P. Himalaya, 4. Nepal Himalaya), and (iii) Eastern Himalaya (5. Daijeeling- Bhutan-Assam Himalaya and 6. Purvanchal).
The Western Himalaya-It is 880 km long from the Indus to the Kali rivers, covering a total area of about 4,33,000 km2 in three states-Jammu and Kashmir, Himachal Pradesh and Uttaranchal. It has three physiographic provinces-Kashmir Himalaya, Himachal Himalaya and Kumaun Himalaya.
The Kashmir Himalaya mostly lies in Jammu and Kashmir State covering an area of about 350,000 sq. km. It is about 700 km long 500 km wide with an average height of 3,000 m. It has the largest share of snows and glaciers.
The main morphological feature of this region is a number of glaciated troughs. The Indus traverses the Kashmir Himalaya diagonally for about 650 km. north of the Indus lies the Karakoram Mountains with lofty peaks and vast glaciers. Steppe and semi-desert like climatic characteristics prevail in this area except in the irrigated valleys.
The two other important areas of the Kashmir Himalaya are the Ladakh plateau and the Vale of Kashmir. The latter is bordered by the Zaskar range in the north and the Pirpanjal range in the south. While D.N. Wadia considers it a structural longitudinal ‘doon’ H. de Terra believes it to be the product of subsidence caused by faulting.
A special feature of the Vale of Kashmir is the Karewa deposits consisting of silt, compact sand and clay and presenting a plateau like topography (80 km long and 5- 26 km wide). Kashmir Himalaya is characterised by high snow covered peaks, deep valleys, interlocked spurs and High Mountain passes.
The Himachal Himalaya lies in Himachal Pradesh covering an area of about 45,000 km. All the three ranges of the Himalaya are well represented here, i.e. Greater Himalaya by Zaskar range, Lesser Himalaya by Pirpanjal and Dhauladhar ranges and outer Himalaya by Siwaliks. The main range has few peaks above 6,000 m.
The northern slopes are bare and show plains with lakes, while the southern slopes are rugged and forest clad. Zojila Rohtang and Bara Lacha La, Imis La and Shipki La are important passes. Himachal Himalaya houses beautiful valleys of Kullu, Kangra, Lahul and Spiti which are noted for their fruit culture and scenic beauty.
The Kumaun Himalayaextends from the Satluj to the Kali river covering a length of about 320 km and encompassing an area of 38,000 km2. Its highest peak Nanda Devi (7817 m), stands within a vast amphitheatre-like valley, about 112 km in circumference with an average height of 7000 m. Other peaks include Badrinath 7069 m), Kedarnath (6940 m), Trisul (7120 m), Mana (7273 m), Kamet (7756 m), Gangotri (6615 m) and Jaonli or Shivling (6638 in). It is in the Gangotri area where the Bhagirathi river, the ultimate source of the sacred Ganga rises in the Gangotri glacier. The region has a number of lakes (numbering 360), remains of which are seen in the form of Nainital and Bhimtal.
In Kumaun Himalaya the Lesser Himalaya is represented by the Mussoorie and Nag Tiba ranges of which the former runs upto Landsdowns covering a length of about 120 km. Its southern slopes are steep. On the eastern side of this range lies the famous Nainital lake.
The Siwalik range (900-1000 m) runs south of the Mussoorrie range between Ganga and Yamuna (length 74 km). The alluvial filled tectonic valley between the Lesser Himalaya and Siwalik range is called ‘Doon’ e.g. Dehradun.
The whole of the Kumaun Himalaya is nested with interlocking spurs and deeply cut incised meanders. Here the relief features are the outcome of both glacial as well as fluvial erosion. In the upperreaches many river valleys exhibit V in U shapes. The Kumaun Hi malaya is connected to Tibet by a number of mountain passes amongst which ThagaLa, Muling La (5669 m), Mana (5611 m), Niti (5068 m), Marhi La (4993 m), Kungribingri, Darma and Lipu Lekh are important.
The Central Himalaya-It stretches from river Kali to river Tista for about 800 km. occupying an area of about 1,16,800 sq. km. Its major part lies outside India in Nepal except the extreme eastern part called the Sikkim Himalaya (in Sikkim) and the Darjeeling Himalaya (in West Bengal).
All the three ranges of the Himalaya are present here. The Greater Himalaya attains the maximum height housing some of the highest peaks of the world like Mt. Everest (8848 m), Kanchenjunga (8598 m), Makalu (8481 m), Annapurna (8075 m), Gosaithan (8014 m) and Dhaulagiri (8168 m).
The Lesser Himalaya in this region is known as Mahabharat Lekh, which is cut through various rivers like Ghaghara, Gandak and Kosi etc. The Kathmandu and Pokhra valleys like the Vale of Kashmir represent lacustrine deposits between Greater and Lesser Himalayas. The Siwaliks become closer to the Lesser Himalaya towards the east and are almost non-existent beyond Narayani (Gandak).
Nepal Himalaya exerts considerable impact on the hydrology of the Terai and the Middle Ganga Plain. Some of the mighty rivers of the Ganga Plain like Ghaghara, Gandak, Kosi and Tista rise in this part of the Himalaya. It has numerous peaks with perpetual snow cover. It has very few mountain passes (Namja 4944 m, Pindu, Gya 5602 m, Nye etc.) through which it is linked with Tibet.
The Eastern Himalaya-This stretches between the Tista and the Brahmaputra rivers covering a distance of about 720 km and an area of about 67,500 km2. This occupies Arunachal Pradesh and Bhutan. After Namcha Barwa the direction of the Himalayas suddenly turns from north to south running along the Myanmar-India border.
The Eastern Himalaya is also called Assam Himalaya. The Assam Himalaya rises very rapidly from the plains, the foothills region being narrow and the sub-Himalayas comparatively lower in altitude than in other areas.
The Assam Himalaya is geographically divided into short segments after the name of the prominent tribes inhabiting the area. These include the Aka hills between the Dhansiri and Dikrai rivers; the Daphla hills between the Bhaireli on the west and the Ranganad on the east; the Miri hills in the northern part of Subansiri division; the Abor hills between the Siom and the Dibang; and the Mishmi hills between the Dibang and the Dihang (Brahmaputra). Kula Kangri (7539 m), Chomo Lhari (7314 m), Towa Dz, Kangto (7090 m), Gyalaperi (7151 m), and Namcha Barwa (7756 m) near the Dihang gorge are the prominent peaks. Assam Himalaya has a number of mountain passes (Jelep La 4538 m), Bum La 4331 m, The La 4740 m, Tunga 5044 m, Yonggyap 3962, Kangri Karpo La 5636 m).
Amongst these Jelep La in the Chumbi valley of Sikkim and Bum La in Arunachal Pradesh are main routes to the Tibetan capital Lhasa. Owing to rugged terrain and thick vegetal cover the Assam Himalaya is very little studied part of the Himalayas. Due to heavy rainfall fluvial erosion is very dominant over these ranges.
The hill ranges running in north-south direction along the Burmese border and passing through Arunachal Pradesh (Tirap division), Nagaland, Manipur and Mizoram are collectively called Purvanchal. These are known by various local names, i.e. Patkai Bum (Arunachal Pradesh), Naga hills, Kohima hills, Manipur hills, Mizo hills, Tripura hills and Barail range. The highest peak of Naga Hills is Saramati peak (3826 m). These hills are heavily forested. While northern Myanmar is connccted through Likhapani (Arunachal Pradesh) the route joins Mandalay (Myanmar) with Imphal (Manipur. India).
The Purvanchal Himalaya is joined by the Meghalaya Plateau in the west. The extension of the Burmese chain continues southward up to Andaman and Nicobar islands and even upto the Indonesian archipelago.