runs parallel to the Ladakh range for some 100 km northwest from Chushul, and extends to the south along the southern shore of the Panggong Lake. It is divided from the main Ladakh range by the Tangtse River. Its highest range is 6700 m, and the northern slopes are heavily glaciated. A third branch called the Kailash Range issues south from the Pangong Range and continues till Mount Kailas in Ngari (in Tibet). It forms the eastern watershed of the Indus River south of Mount Sajum. Zanskar range The Zanskar Range consists of layers of sediment from the ocean floor, and the Ladakh Range of granite was born of the immense heat generated by the friction between the two plates. In Ladakh, the suture zone between the continental masses runs a little to the south of the Indus Valley. The drift continues and is the cause of the frequent earthquakes in the Himalayan region. Crossing the Himalayas by the dip of the Zoji-la, the crest-line of the range remains at a relatively modest level, the highest peaks near the pass being little more than 5000–5500 m above sea level. South-east of Zoji-la the scale increases, reaching a climax in the mighty massif of Nun-Kun, with two summits over 7000 m. Rivers and valleys The enormous mass of the Himalayas creates a rain shadow, denying entry to the moisture-laden clouds of the Indian monsoon. Ladakh is thus a high altitude desert. The main source of water is the winter snowfall on the mountains. The regions on the north flank of the Himalayas—Dras, the Suru valley and Zanskar—experience heavy snowfall and remain virtually cut off from the rest of the country for several months in the year. Summers are short, although long enough to grow crops. The proportion of oxygen is less than in many other places at a comparable altitude because of lack of vegetation. There is little moisture to temper the effects of rarefied air. Suru and Zanskar valleys form a great trough at the foot of the northern, heavily glaciated flank of the Himalayas, while opposite rise the mountains of the Zanskar range. Indus river and valley Indus River is the backbone of Ladakh; all the major places historically and currently such as Shey, Leh, Basgo, and Tingmosgang are situated close to the river. Zanskar river and valley Zanskar valley consists of troughs of two rivers, the Stod (Doda)