Deposition
Topic: Geomorphic Processes: Weathering, Mass Movement, Erosion and Soil Formation · NCERT: Class 11, Ch 5 "Geomorphic Processes"; Class 11, Ch 6 "Landforms and their Evolution"
Meaning
Deposition is the laying down of material that an agent was carrying. The agent may be running water, a glacier, wind, waves or groundwater. When the agent slows down on a gentler slope, it loses energy and drops its load. Coarse material settles first, and fine material settles later. Over time, deposition fills up hollows and low areas. It is part of aggradation (building up of low land). Deposition is a result of erosion, not really the "work" of any agent.
Example
The Ganga drops coarse sand and gravel where it leaves the Himalayas. It carries fine silt and clay much further and lays them down across the Indo-Gangetic plains and the Ganga-Brahmaputra delta in West Bengal and Bangladesh.
Don't confuse with
- Erosion: the picking up and carrying away of material. Deposition is the dropping of it.
- Mass movement: debris piling up at the foot of a slope is moved by gravity alone, not dropped by a slowing agent.