Himalaya forms nearly 2600km broad arc with its width that averages from 320 km to 400 km, hemispherical through Nepal and Bhutan, bound to the north by Tibetan plateau Qing Zang Gaoyuan and to Indian subcontinent from Indus River in the northwest to Brahmaputra River in the east.
Topographically, Himalaya has been classified into four longitudinal parallel belts:
1. Himadri or Great Himalayas or Higher Himalayas
Being the longest and continuous, Himadri dominates the larger sections of Himalaya, mostly north part of Nepal and parts of Sikkim. Lying on the north of Himachal, it accommodates majestic snow-capped peaks that have average altitude of about 6100 m (20,000 ft). This belt is bordered in the north by Indus River and has deep gorges. Eight of the world’s fourteen highest peaks lying 8000 m above sea level in Nepal rest in this Himalayan range.
2. Himachal or Middle Himalayas or Lower Himalayas
Himachal lies lower than Himadri in the south and north of Siwalik. It extends from East to West and has an average altitude ranging from 3700m (12,000) – 4500m (15,000 ft). With a width of about 80 km (about 50 mi) it is spread across north of Rawalpindi district of Pakistan covering the districts of Batagram, Mansehra, Abbottabad and Pakistani territories of Kashmir. It also touches Jammu and Kashmir, Himachal Pradesh and Western Uttar Pradesh of India, Nepal and the North-Eastern Himalayas. It boasts the Himalayn peaks that rise up to 7300m (24,000 ft) or more above sea level. Nag Tibba, the Dhaola Dhar, the Pir Panjal and the Mahabharat are the Himachal ranges. Forest-laden regions, gorges, glaciated passes and fertile valleys also characterize Himachal.
3.Shivalik or Outer Himalayas or Sub-Himalayas
Shivalik is the lowest and narrowest section of Himalaya and has an average altitude about 900m (3000ft) to 1200m (4000 feet). It extends across the southernmost belt of the Himalayan range with a width of only 16 km in places, touching the regions of North India and Pakistan. Long and flat-bottomed valleys are the distinct characteristics of Shivalik.
4.Trans-Himalayas or Tibetan Himalayas
Trans-Himalaya stretches across Himalaya from West to East for about 1,000 km and its altitude varies from 4500 to 6600m above sea level. In this belt, Brahmaputra, Indus and Satluj River are found which originate in Tibet and traverse across the Himalayas. From a total of nearly 2.6 million sq. km. area Trans-Himalaya encompasses 186,200 sq. km area in India administered Jammu and Kashmir and Himachal Pradesh and the regions of Tibetan plateau. Trans-Himalaya houses Zanskar, Ladakh and Karakoram ranges that lie in the rain-shadow region to the north.
Himalayas are also divided into following categories on the basis of international political boundaries:
Himalaya extends across three fourths of the area in Nepal. Ranging in altitude from 4877m to 8848m, Nepalese Himalaya houses eight of the world’s fourteen highest snow-capped peaks; Mt. Everest [8,848m], Kanchenjunga [8,586m], Lhotse [8,516m], Makalu [8,463m], Cho Oyu [8,201m], Dhaulagiri [8,167m], Manaslu [8,163m] and Annapurna [8,091m]. It has three parallel bands that run that stretch from northeast to the southwest; Great Himalaya dominates the north of Nepal and to the south there are intermediate ranges at an altitude of 8,000-14,000 ft including Mahabharat and Churia ranges. Nepalese Himalaya boasts the rich ecology- fertile lowlands, glaciated passes, Himalaya glaciers, high-desert trans-Himalayan region, arid valleys of Mustang, Manang and Dolpo, and terrains that are swampy, highest, rugged, remote and difficult terrain. Himalaya range on the western and central Nepal borders Nepal and China and this border ranges in altitude from 5,000 to 6,000m which despite being less rugged has harsh climate. Bhot valleys rest between this border and the main Himalayan range. �Kathmandu is the capital of Nepal.
Tibetan Himalaya is most popular as the highest plateau in the world and covers the southern part of Tibet. It encompasses 1,000 km [600 miles] with a width ranging from 225 km [140 miles] to about 32 km [20 miles]. River gorges do not divide this Himalaya but has passes that average to 5,330 m [17,500 ft] in altitude amongst which Chargoding Pass is the highest pass elevated at an altitude 5,885 m [19,308 ft]. Tibetan Himalaya houses the highest mountains like Mt Everest [8,848 m] which happens to be the highest mountain in the world, Namcha Barwa [7,756 m] around which the Brahmaputra carves a fantastic gorge to enter India and Gurla Mandhata [7,728 m]. Tibetan Himalaya houses some of the largest Himalaya Rivers.
Indian Himalaya runs across the northern boundary of India, Jammu and Kashmir, Himachal Pradesh, Uttar Pradesh, Sikkim and Arunachal Pradesh from west to east. Jammu & Kashmir region of Indian Himalaya comprises of Jammu foothill plains, the lakes and valleys of Kashmir and the high altitude plains and picturesque mountains of Ladakh. Srinagar is Kashmir’s summer capital and Jammu, the winter capital. Snow, lofty peaks, cascading streams, alpine meadows & lush fruit-laden valleys characterize Himachal Pradesh and its capital is Shimla. Uttaranchal region of Indian Himalaya lies in the north of India and has eight hill districts. Sikkim is one of the smallest Indian states and its Himalaya region is connected to Nepal in the west, to Bhutan in the east, Tibet in the north and northeast and to West Bengal in the south. Arunachal Pradesh lies on India’s north-east frontier and is bound to Assam to the south, Nagaland to the south east, and Myanmar to the eastern side and Bhutan to the west. There is the Line of Actual Control to the north that separates this Himalaya region from China. Its capital is Itanagar.
Bhutan Himalaya hugs the eastern ridges of the Himalayas. Its northern and western boundary with Tibet runs along Great Himalaya crest. It is bound to India in the south of the Himalaya Range by the Duars Plain; Bhutan Himalaya lies to the south of West Bengal and Assam, to the east of Arunachal Pradesh and to the southwest Sikkim. Thimphu is the capital of Bhutan. Physically, from north to south Bhutan can be divided into the Great Himalayas region, the Lesser Himalayas region and the Duars Plain. Lesser Himalayas of Bhutan houses fertile valleys of central at an altitude from 5,000 to 9,000 feet. Narrow Duars Plain lies on the south of the Lesser Himalayas and the foothills and it forms 8 to 10 miles wide strip along the southern border of Bhutan.