The Himalayas:-

The Himalayans mountain system developed in a series of stages 30 to 50 million years ago. The Himalayan range was created from powerful earth movement that occurred as the Indian plate pressed against the Eurasian continental plate. The earth movements raised the deposits laid down in the ancient, shallow Tethys Sea to form the Himalayan ranges from Pakistan eastward across northern India, and from Nepal and Bhutan to the Myanmar border. Even today the mountains continue to develop and change, and earthquakes and tremors are frequent in the area.

Physically, the Himalayas forms three parallel zones; the Great Himalayas, the Middle Himalayas, and the Sub-Himalayas, which includes the Siwalik Range and foothills and the tarai and Duars piedmont. Each of these lateral divisions exhibits certain similar topographic features. The great Himalayas, the highest zone, consists of a huge line of snowy peaks with an average height exceeding 6100 m (20,000 ft). The width of this zone, composed largely but not entirely of gneiss and granite is about 24 km. Spurs from the Great Himalayas project southwards into the Middle Himalayas in an irregular fashion. The Nepal and Sikkim portion the Great Himalayas contains the greatest number of high peaks. The snow line on the southern slopes of the Great Himalayas varies from 4480 m in the eastern and central Himalayas of Nepal and Sikkim to 5180 m (17,000 ft) in the western Himalayas. To the north of the Great Himalayas are several ranges such as the Zaskar, Ladakh, and the Kailas. The Karakoram Range lies on the Tibetan side of the Great Himalayas.

The great Himalayan region is one of the few remaining isolated and inaccessible areas in the world today. Some high valleys in the Great Himalayas are occupied by small clustered settlements. Extremely cold winters and short growing season limit the farmers to one crop per year, most commonly potatoes or barley.

The Middle Himalayas range, which has a width of about 80 km, borders the great Himalaya range on the south. It consists principally of high ranges both within and outside of the great Himalayan range; some of the ranges of the Middle Himalayas are the Nag Tibba, the Dhaola Dhar, the Pir Panjal, and the Mahabharata. The Middle Himalayas possess a remarkable uniformity of height; most are between 1830 and 3050 m.

The Himalayas influences the climate of the Indian subcontinent by sheltering it from the cold air mass of Central Asia. The range also exerts a major influence on monsoon and rainfall patterns. Within the Himalayas climate varies depending on elevation and location. Climate ranges from subtropical in the southern foothills, with average summer temperatures of about 60 degree centigrade and average winter temperatures of about 18 degree centigrade. Warm temperate conditions in the Middle Himalayan valleys, with average summer temperatures of about 25 degree centigrade  and cooler winters; cool temperate conditions in the higher parts of the Middle Himalayas, where average summer temperature are 15 to 18 degree centigrade and winters are below freezing; to a cold and winters are severe. At elevations above 4880 m (16,000 ft the climate is very cold with below freezing temperatures and the area is permanently covered with snow and ice. The eastern part of the Himalayas receives heavy rainfall; the western part is drier.