Short notes on Topography of Himalya

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The Himalayas form a highly rugged and continuous stretch of high mountainous country which lies between the Indus in the west and Brahmaputra in the east. They are among the young­est fold mountains of die world.

Their uplift rejuve­nated the old rivers some of which have cut out deep gorges across these ranges to reach the Northern Plain and have proved dieir antecedent characteris­tics, e.g. Brahmaputra, Kali, Satluj, and Indus. They exhibit practically all those landforms which de­velop when strata are intensely folded. Examples of anticlinal ridges, synclinal valleys, overfolds and recumbent folds are common.

At some places die compression was so intense diat folded strata were first torn across and dien pushed off forming nappes. Intermontane plateaus and large-sized basins are conspicuously absent. The Vale of Kashmir, about 135 km. long and 40 km. broad, is the only large level strip of land in the Himalayas. It is perhaps a synclinal valley in which die Jhelum has deposited its sediments to form die level stretch of land.

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The Himalayas have deep cut V-shaped val­leys of such high gradient that large pebbles (0.6 cm across) of crystalline rocks are carried down swiftly to the piedmont zone.

The valleys although rela­tively straight viewed from a high level plane or space satellite, are fairly sinuous in detail marked by interlocking spurs. The awe-inspiring slopes and heights of the densely forested ridges, hills and ranges of the lesser Himalayas fade into relative insignificance as the snow clad Great Himalayas are approached.

Here we have a mountain glacial land­scape marked by moraines, pyramidal peaks, corries, aretes, etc; with peri-glacial features, e.g. strong solifluction occurring further downwards. Even above the snow-line where the peak slopes are too steep to allow snow accumulation die structures are nicely exposed.

In the Himalayas snow fields cover about 40,000 sq. km of areafrom Kashmir to Assam. These snow fields feed the valley glaciers and provide uninterrupted supply of water to the perennial rivers of the Ganga Plain. The height of snow line varies between 4000-5800 m in the east and 4500-6000 m in the west. It also oscillates between 4500-6000 m along die soudiem face and 5500-6000 m along the northern one.

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The Himalayas are not single continuous chain or range of mountains, but a series of several more or less parallel or converging ranges. These are inter­sected by numerous valleys like Kashmir valley, die Karewas, the Doon valley, the Kangra and Kullu valley (Himachal Pradesh), Kathmandu valley (Ne­pal), Bhagirathi valley (nearGangotri) and Mandakini valley (near Kedamath). These are places of tour­ists’ attraction and support large clusters of popula­tion.

If die Davisian cyclic concept of landscape evolution were accepted one would place the Hima­layas, as a whole, in die mature stage of die first cycle of erosion, one of die notable characteristics of which is the inversion of relief.

Such inversion of relief where anticlines form valleys and synclines form peaks and ridges is die rule rather than exception in the Himalayas. This is true of all the areas extending from the Great Himalayas (Nanda Devi) to the foothills (e.g. Banali hills in Tehri Garhwal foothills) and from Kashmir to the eastern limit of the Himalayas (E. Ahmad, 1992, p. 25).

River terraces are quite frequent both in Great and Lesser Himalayas. Bose has noted several cases of river terraces along the source streams of the Ganga, e.g. Bhagirathi, Alaknanda and Pindar above Devaprayag (S.C. Bose, 1968).

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Such terraces occur­ring in a series of three or four, sometimes paired on either side of a stream which in some cases is digging a ‘V’-shaped profile within a broader U- shaped valley, were taken to be evidence of intermi­ttent uplift (E. Ahmad, 1971).

The configuration of the valleys in the inner Himalaya of Kashmir regions is very peculiar, most of the valleys showing abrupt alternation of deep U- shaped or I-shaped gorges, with broad shelving valleys of an open V-shape.

The Himalayan section of the Ganga and its tributaries have remarkably ‘V’-shaped cross sections-the slope being 30% near Gangotri, 23% near Devaprayag and 7% near Haridwar. But in the eastern Himalayas the slope is comparatively greater due to higher altitude in a relatively narrow belt across which the streams run transversely.

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