Zemu Glacier The Zemu glacier is situated in a large U-shaped valley at the base of the Kanchenjunga massif in northwestern Sikkim. It has a length of about 26 km and is the largest and the most famous glacier of the eastern Himalaya. The Teesta River rises from the snout of this glacier.

Credit: Discover India

Northern Sikkim
In northern Sikkim are situated the inner dry valleys lying in the rainshadow of the main Himalayan range. These areas have cold desert-like conditions, although the aridity is much less than that of places like Ladakh. The average elevation is more than 3,000 m with an extremely rugged terrain. There are two main valleys in the region -- the Lanchung Valley and the Lachen chu Valley.

Both the Lanchung and Lachen chu rivers are tributaries of the Teesta River. The latter narrows down considerably in its higher reaches before taking an abrupt turn through the gap at Gagong at the base of the spectacular Chomoyomo mountains. Here the terrain converges with the head of the Lanchung Valley over the 6,000 m high Donkya La Pass across which the plateau first descends and then rises towards the Indo-Tibetan border.

The two main mountain ranges of the tract are the Donkya and Chomo Lhari mountains. Two important passes across them are the Jelep La and Nathu La, both having an elevation of more than 4,000 m.