<P> Darjeeling Himalayan hill region is situated on the north - western side of the state . This region belongs to the Eastern Himalaya range . The whole of the Darjeeling district except the Siliguri division and a narrow part in the northern part of Jalpaiguri district constitutes the region . It starts abruptly up from the Terai region . The deep gorge of Teesta River has divided this mountainous region into two parts: the Singalila and Darjeeling ranges run from north to south in the western part . The Singalila range is located along the border of Darjeeling and Nepal; it has four important peaks--Sandakfu, Falut, Sabargam and Tonglu . Among the Himalayan ranges of this region, Singalila range hosts Sandakfu which at 3,636 metres (11,929 ft) is the highest point of West Bengal. Also to mention Sandakfu & Phalut are the only place in West Bengal from where Mt . Everest is visible . Two high peaks, Tiger Hill and Ghoom are seen near the town of Darjeeling . Many ranges branch off in different directions from Tiger Hill . Durpindara is an important mountain in the eastern part of the mountainous region . A few hills also occur in the Terai or Dooars region at the foot of the Himalayas . Some remnants of the Siwaliks can be seen in the Jalpaiguri district, where they are known as the Buxa - Jayanti Hills . </P> <P> The' ' Terai' ' ("moist land") is a belt of marshy grasslands, savannas, and forests at the base of the Himalaya range stretching southwards to about 38 km . Above the Terai belt lies the Bhabar, a forested belt of rock, gravel, and soil eroded from the Himalayas . The Terai zone is composed of alternate layers of clay and sand, with a high water table that creates many springs and wetlands . The Terai zone is inundated yearly by the monsoon - swollen rivers of the Himalaya . The Terai - Duar savanna and grasslands is an ecoregion that stretches across the middle of the Terai belt . The Terai - Duar savanna and wetlands are a mosaic of tall grasslands, savannas and evergreen and deciduous forests . The Terai and Dooars region politically constitute the plains of Darjeeling District, whole of Jalpaiguri and Alipurduar district and upper region of Cooch Behar District in West Bengal . The slope of the land is gentle, from north to south . The general height of the land is 80 to 100 m . The entire region is made up of sand, gravel and pebbles laid down by the Himalayan rivers like the Teesta, Torsa, Raidak, Jaldhaka, Sankosh and several other small rivulets . The Teesta has divided the area into two parts - the western part is known as the Terai whereas the eastern part is known as the Dooars or Duars . The Dooars region can be further subdivided into the Siliguri or Western Dooars, the middle or Jalpaiguri Dooars and the eastern or Alipur Dooars . </P> <P> North Bengal plain start from the south of Terai region and continues up to the left bank of the Ganges . The southern parts of the district Jalpaiguri, North Dinajpur baring some extreme northern regions, South Dinajpur, Malda, Alipurduar and southern part of Cooch Behar districts constitute this geographical region . The narrow land mass in the North Dinajpur district is known as Mahananda Corridor . This corridor runs north to south joining Malda with the plains of Jalpaiguri, Alipurduar and Cooch Behar . The entire part of North and South Dinajpur is silt laden plain . </P> <P> Mahananda River divides the district of Malda into two parts . The eastern part consists of undulating plains and some tilas and is made up of old alluvium and is a part of the Ganges delta . It is also known as Barind or Barendrabhumi . In contrast to the eastern part, the western part is made up of new alluvium and in this part River Kalindi joins the Mahananda River . The part of Malda lying to the north of river Kalindi is known as tal . This is a lowland and covered with swamps and beels (small water bodies). Whereas the area south of the Kalindi is a very fertile land and is known as diara . </P>

Which is the easternmost river of the north bengal plains