Himalayas (hĭmälˈəyəz, hĭməlāˈəz) [key] [Sanskrit, = abode of snow], great Asian mountain system, extending c.1,500 mi (2,410 km) E from the Indus River in Pakistan through India, the Tibet region of China, Nepal, E India, and Bhutan to the southern bend of the Brahmaputra River in SE Tibet. For most of its length, the Himalayas comprise two nearly parallel ranges separated by a wide valley in which the Indus and Sutlej rivers flow westward and the Brahmaputra flows eastward. The northern range is called the Trans-Himalayas. The southern range has three parallel zones: the Great Himalayas, the perpetually snow-covered main range in which the highest peaks (average elevation 20,000 ft/6,100 m) are found; the Lesser Himalayas with 7,000 to 15,000 ft (2,130–4,570 m) elevations; and the southernmost Outer Himalayas, 2,000 to 5,000 ft (610–1,520 m) high. A relatively young and still growing system subject to severe earthquakes, the Himalayas' main axis was formed c.25 to 70 million years ago as the earth's crust folded against the northward-moving Indian subcontinent. Some 30 peaks rise to more than 25,000 ft (7,620 m), including Mt. Everest (29,029 ft/8,848 m) and Kanchenjunga (28,208 ft/8,598 m), the world's highest and third highest peaks. Himalayan peaks have long been the goal of mountaineers. The towering ranges are penetrated by many roads and tracks, and air flights reach remote towns. Railroads reach only the southern foothills; from there the main route follows footpaths across primitive bridges, ropeways, and high mountain passes. Improved roads run between Kashmir and China and from India through Nepal to China, and there are major airports at Katmandu and Srinagar. The aridity of the Tibetan plateau and the Tarim basin of W China results from the interception of the moisture-laden northwest monsoon by the Himalayas' southern face. Consequently, the northern slopes receive relatively light snowfall and have little drainage, while the snow-covered and extensively glaciated southern slopes give rise to the Indian subcontinent's major rivers, including the Indus, Sutlej, Ganges, and Brahmaputra. Little of the region is inhabitable or of great current economic value. The southern piedmont plains of Tarai and Duars were formerly malarial jungle and swamps but have been converted to agriculture, with many wild animals in nature preserves. Grazing is possible on some of the gentler slopes, and extensive farming is carried on in the valleys; there is some lumbering in the forests found below 12,000 ft (3,660 m). Limited amounts of iron ore, gold, and sapphires are worked in the west. The Himalayan rivers offer much scope for hydroelectric power and irrigation. Hill resorts such as Shimla, Naini Tal, Mussoorie, and Darjeeling are popular summer retreats from the heat of the Indian plains. The Himalayas are associated with many legends in Asian mythology (see abominable snowman); on isolated slopes are found the retreats of rishis (holy sages), gurus (teachers), and Tibetan monks.