Lateral and vertical erosion
Also called: Downcutting · Topic: Landforms and their Evolution: Rivers, Groundwater, Glaciers, Waves and Wind · NCERT: Class 11, Ch 6 "Landforms and their Evolution"
Meaning
A river erodes in two directions. Vertical erosion, or downcutting, deepens the river bed. It dominates on steep slopes, where the water flows fast, so the valley becomes deep and V-shaped. Lateral erosion cuts into the banks sideways. It dominates on gentle slopes and widens the valley. Over a long time, it wears hills and valleys down into plains.
Example
Vertical erosion: the Indus has cut a deep gorge near Gilgit in the Himalaya. Lateral erosion: the Ganga in the plains of Bihar keeps cutting its banks and makes its valley wider.
Don't confuse with
- Headward erosion: here a valley grows longer at its head, towards the source, by cutting backwards. Vertical erosion makes a valley deeper, and lateral erosion makes it wider.