A gorge is a very steep-sided, narrow river valley. It is found in the mountains in the upper courses of the rivers. They are near I-shaped in appearance. In the upper course the river is very swift as it descends down the steep slopes of the mountains. Vertical corrosion or downcutting is the predominant action of the river here. In areas where the rocks are very hard or resistant, the valley that develops in narrow and the sides are steep rising almost vertically. Such narrow river valleys are called gorges. Thus, gorges are found in mountainous terrain with resistant rocks. They are usually found in the upper reaches of the river in high mountains, e.g. the Indus Gorge, the Brahmaputra Gorge.
Gorges are the features of youthful topography. In the Himalayas where the land has been uplifted in recent geological period, gorges are common.
