Terai
The Terai region is composed of a 26 to 32 km wide broad belt of alluvial and fertile plain in the southern part of the country. This belt extends from the westernmost part of the country to the eastern limit and covers about 17% of the total land area.
In between the Chure hills, rising abruptly to the north of the southern plains and the Mahabharat range, are a number of low valleys called "Duns". The Duns resemble the Terai in relief and climate and are also called the Inner Terai. The Chure range running east west across the country is shaped like a hedge. The hills of this range are rather sparsely forested, averaging 600 to 1220 meters in altitude and 8-16 km in breadth. The soil is immature and dry.
Geology of the Terai
The Terai is the Nepalese portion of the Indo-Gangetic Plain that extends from the Indian Shield in the South to the Siwalik Fold Belt to the North. The plain is a few hundred metres above sea level and usually 400 to 600 m thick. it is composed of Recent of Quaternary alluvium, boulder, gravel, silt and clay. Terai Plain is underlain by a thick, relatively flat-lying sequence of Mid to Late Tertiary molasse (Siwalik Group) which uncomformably overlies subbasins of early Tertiary to Protorozoic sediments (Surkhet, Gondwana and Vindhyan Groups) and igeneous and metamorphic rocks of the Indian Shield (Agrawal, 1977; Acharya and Ray, 1982; Raiverman et.al, 1983).
SOURCE: geocities.com/geologyofnepal
