Describe longitudinal division of the Himalayan mountains?
Answers
Longitudinally the Himalayas consist of three parallel ranges from south to north and a trans- Himalayan region.
(a) The Sub Himalaya or Siwaliks-it is also known as the outer Himalaya. This is the southernmost range of the Himalayas bordering the Ganga Plain and giving a hog-back appearance with relatively steeper slopes towards south. Flat scarps, anticlinal crests and synclinal valleys with an average elevation of 600 m characterise this range. It is bordered at the top by scarps and descends northwards to flat floored structural valleys called 'doon' or 'dun' in the west and 'duar' in the east which are intensively cultivated and densely populated. The site of Dehradun lies in one such valley (75 km x 20 km) which is covered with boulder and clay deposits.
The range has a total length of about 2400 km from the Indus gorge to the Brahmaputra valley. It is known by various local names, i.e. the Jammu hills (Jammu & Kashmir), the Dundwarange (Uttaranchal), the Churia Muria hills (Nepal), the Daffla, Miri, Abor and Mishmi hills (Arunachal Pradesh).
Most of the rivers descending from the northern ranges of the Himalayas have carved out wide and steep-sided valleys. The gorges of the Tista and the Raidak have jointly formed a 90 km gap in the Siwalik range. The range is covered with thick, tropical moist deciduous forests. It enjoys good amount of rainfall and suffers heavy erosion. Its southern slopes are barren and highly dissected.
(b) The Lesser Himalaya or Himanchal-this range lies north of the Siwalik range from which it is separated through M.B.T. It consists of parallel ranges in Nepal and Punjab but of scattered mountains in Kumaun. Important ranges include the Dhauladhar, Pirpanjal, Nag Tiba, Mahabharat range and Mussoorie range. Of these the Pirpanjal range of Kashmir is the longest and the most important one. It runs for 400 km between the Jhelum and the Beas.
(c) The Greater Himalayas or Himadri-this is a most continuous, loftiest and northern most range of die Himalayas. It has a core of Archaean rocks (granites, gneisses and schists) flanked by 41 metamorphosedsedimentaryrocks. The range houses most of die snowy peaks and ridges of the Himalayas.
The average height of the range is 6100 m, whereas many peaks exceed 8000 m (Mt. Everest 8848 m, Kanchenjunga 8598 m, Makalu 8481 m, Dhaulagiri 8172m, Mansalu 8156, ChoOyu 8153 m, Naga Parbat 8126 m and Annapurna 8078 m). Few passes occur in these ranges though at very high elevation (over 2500 m) and remain snowbound for most part of the year.
The Burzil pass and Kashmir, B ara Lapcha La and Shipki Lain Himachal Pradesh, Thaga La, Niti Pass and Lipu Lekh Pass in Uttaranchal, and Nathu La Jelep La in Sikkim are worthy of mention. The Hindustan-TibetRoad, which joins Shimla with Gartok in western Tibet passes through die Shipki La in die Satluj valley. Another j important trade route connects Kalimpong in West Bengal widi Lhasa the capital of Tibet, through Jelep La in the Chumbi valley in Sikkim.
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 northern most range is known as the Great or Inner Himalayas or the 'Himadri