Gradation
Topic: Geomorphic Processes: Weathering, Mass Movement, Erosion and Soil Formation · NCERT: Class 9, Ch 2 "Shaping of the Earth's Surface"; Class 11, Ch 5 "Geomorphic Processes"
Meaning
Gradation means wearing down the earth's relief (the ups and downs of the land) through erosion. It has two parts. Degradation wears high areas down. Aggradation fills up basins and hollows. Gradation works to even out the surface, but endogenic forces keep raising new land. So the surface never becomes flat.
Example
Rivers degrade the Himalayas by cutting into and carrying away rock. They aggrade the Indo-Gangetic plains by spreading thick layers of alluvium (river-laid silt and sand).
Don't confuse with
- Diastrophism: this raises and moves the crust, so it is not a gradational process. Erosion and deposition are gradational.
Related concepts
- Endogenic and exogenic forces
- Endogenic forces
- Exogenic forces
- Geomorphic processes
- Geomorphic agent