The Himalaya, stretching from the Nanga Parbat (8126 m) in the west to the Namche Barwa (7756 m) in the east, forms an arcuate mountain belt and a rampart for the Indian subcontinent along its northern margin (Fig. 1.1). It comprises the earth s largest mountain range with its varied geotectonic zones (Fig. 1.2). From time immemorial the Himalaya has been the source of poetic and spiritual inspiration. It has, ever since the advent of man, sustained several civilizations that flourished on the plain that bordered along its southern margin with its perennial rivers, lush green forests along its slopes and the fertile soil of the land that lay at its feet.