A rift valley is formed when a block of land sinks between two parallel faults. The Narmada River flows through the Narmada-Son rift valley in central India, which runs roughly east-west. Unlike most peninsular rivers that flow west or east, Narmada flows westward through this tectonic valley. Ganga and Brahmaputra flow through Himalayan-alluvial plains, while Krishna flows through the Deccan Plateau but not through a rift valley.