Gorge

A narrow, steep-sided valley or ravine with near-vertical walls, cut by a river through resistant bedrock, typically where vertical erosion greatly exceeds lateral erosion. Gorges often form where rivers are superimposed or antecedent relative to uplifted terrain, or where hard rock resists widening. India's deepest gorges include those carved by the Indus, Sutlej, and Brahmaputra rivers through the Himalayas — particularly the Brahmaputra Gorge (also called the Yarlung Tsangpo Grand Canyon), which at over 5,000 m depth is among the world's deepest, making gorges a recurring UPSC topic in river geomorphology.