The Himalayas are the highest mountain range in the world. It lies in Asia, in the territories of India, China, Nepal, and Pakistan, between the Tibetan Plateau on the north and the Indo-Gangetic Plain on the south. The Himalayas are also the world’s greatest mountain system, with the tallest peaks, fourteen of which are higher than 8,000 m (26,247 ft) of altitude. Their greatest differences in elevation are over short distances, forming the deepest gorges (as much as 4-5 km). The Himalayas are more than 2,400 km long, extending from west to east, roughly forming an arch. The system has an average width of 250 km, the widest portion being 350-km wide. These mountains cover an area of 650,000 km2, approximately.
The Himalayas have precise morphological and physical-geographical borders: on the north, the longitudinal tectonic valleys of the upper courses of the Indus and Tsangpo (Brahmaputra) rivers; on the south, the northern edge of the Indo-Gangetic Plain; on the northwest, the Hindu Raj Range; and on the east, the gorge of the Brahmaputra River. The Himalayas are the major orographic, climatic, and floristic barrier between the deserts of Central Asia and the tropical landscapes of south Asia. However, because antecedent gorges of the Indus, Sutlej, Karnali, and Arun rivers flow through the range, the watershed of the Indian Ocean basin and of an indefinite region of Central Asia passes not through the Himalayas but through the mountain systems bordering it on the north—the Karakoram and the Trans-Himalayas.
The fourteen eight-thousanders
Although the Himalayas average height is about 6,000 m, there are 14 peaks higher than 8,000 m; hence their name the 'eight-thousanders'. They are: Mount Everest: 8,848 m (29,030 ft), which is the world’s highest; K2: 8,611 m (28,251 ft); Kangchenjunga: 8,586 m (28,169 ft); Lhotse: 8,516 m (27,940 ft); Makalu: 8,485 m (27,838 ft); Cho Oyu: 8,188 m (26,864 ft); Dhaulagiri I: 8,167 m (26,795 ft); Manaslu: 8,163 m (26,781 ft); Nanga Parbat:8,125 m (26,657 ft); Anna Purna: 8,091 m (26,545 ft); Gasherbrum I: 8,080 m (26,510 ft); Broad Peak: 8,051 m (26,414 ft); Gasherbrum II: 8,034 m (26,358 ft); Shishapangma: 8,027 m (26,335 ft).
Geological Structure
The Himalayas are young mountains whose orogeny (mountain-formation process) began about 51 million years ago, during the Tertiary period of the Cenozoic era. They are the result of the collision of the Indian Plate against the Eurasian Plate, which thrust-faulted, uplifted and folded up several geological strata to high altitude. The basal rocks of the whole system are precambrian gneiss and granite. Above 7,000 m, Mesozoic crystalline limestone and schist form the highest peaks.
Between the 7,000 and 8,600 m of altitude, there is a geological formation known as the 'Yellow Band'. This geological band consists of middle Cambrian diopside-epidote-bearing marble, which weathers a distinctive yellowish brown, and muscovite-biotite phyllite and schist.
Climate
The Himalayas form a sharp climatic division between the equatorial monsoon region of Hindustan and the continental region of Central Asia. The climate of the western Himalayas is characterized by sharp fluctuations in temperature and by strong winds. The winter is cold (average January temperature, −10° C to −18° C), with violent snowstorms above 2,500 m. The summer is warm (average temperature in July is about 18° C) and dry. The influence of the monsoons is not great and is noticeable only in a certain increase in humidity and cloudiness in July and August. Precipitation (about 1,000 mm per year) is associated with cyclones, during which three to four times less rain falls in the valleys and depressions than on the mountain slopes. The major passes are free of snow at the end of May.
In the western Himalayas at an altitude of 1,800 to 2,200 m are located most of the climatic health resorts of India (Shimla, for example). The eastern area has a hotter and more humid climate, with monsoon rainfall; 85-95 percent of the yearly precipitation falls from May to October. In summer, at a height of 1,500 m, temperatures on the slopes reach 35° C; in the valleys, temperatures reach 45° C. Rain falls almost continually. On the southern slopes (at a height of 3,000 to 4,000 m), precipitation ranges from 2,500 mm in the west to 5,500 mm in the east; in the interior regions, it is about 1,000 mm.
In winter, at a height of 1,800 m, the average January temperature is 4° C; higher than 3,000 m, the temperatures are below freezing. Snowfall occurs annually above 2,200-2,500 m elevation; in the valleys, there are dense fogs. The northern slopes of the Himalayas have a cold mountain-desert climate. The daily temperature ranges as much as 45° C; rainfall is about 100 mm per year. In summer, at a height of 5,000 to 6,000 m, the temperature is above freezing only during the day. The relative humidity of the air is 30-60 percent. In winter, the snow often evaporates without melting.
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| Above, a portion of the Himalaya in Tibet in the Summer. |
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| A map of Asia showing the exact location of the Himalayas Mountain Range. |