Great the Himalayas , the highest a mountain chain in the world, are stretched along northern borders of Pakistan, India, Nepal, Bhutan and Burma. They have been generated as a result of collision of the Indian subcontinent with Asia. This tectonic process proceeds, and gradual drift on the north of the Indian subcontinent calls till now earthquakes.
The System of the Himalayas, about 2400 kilometres at length and various on width from 240 to 330 kilometres, consists of three parallel ridges - the Big Himalayas, the Small Himalayas - sometimes under the general name of a ridge of the Himalayas.
The big Himalayas, or northern ridge, on the average about 6000 metres in height also contains three highest mountains on ground: mount Everest (8796 metres) on Chinese-Nepalese border; Ê2 (8611 metres, also known as the mountain Godvin-Osten) is challenged by India, Pakistan and China, and Kanchenjunga (8598 metres) on indijsko-Nepalese border. Many large mountains are completely in India, such as Nanda Devi (7817) in state of Uttar Pradesh.
Snow line on the average 4500 to 6000 metres on a southern slope of the Big Himalayas and 5500 to 6000 on northern slope.
The Small Himalayas, are possessed in a northwest part of India in states Himachal Pradesh and Uttar Pradesh, in the North central India in state of Sikkim, and in the northeast of India in state of Arunachal Pradesh, in a range from 1500 to 5000 metres in height.
The Southern Himalayas, on the average from 900 to 1200 metres above sea level, is between the Small Himalayas and Indo-Gangetic plain. In state of Himachal Pradesh and Uttar Pradesh, this southern ridge name often as Shivalik. It is possible to define also the fourth, and northern ridge known as the Trance-gimalai. Though the Trance-gimalai is separateed from the Himalaya ridge throughout a more part of the length, they merge together in the western part - a ridge of Karakorum - where borders of India, Pakistan and China incorporate.
Southern slopes of the Himalaya ridges too abrupt to accumulate snow or to support a life of trees; northern slopes are routinely covered by woods below a snow line. Between ridges there are extensive high plateaus, penetrating gorges and fertile valleys, such as valleys of Kashmir and Kulu. The Himalayas serve very important purpose. They supply the physical screen in which the system of monsoons works and are a source of the big river systems. As a result of erosion, the rivers flowing from mountains bear a large quantity of silt which enriches plains.