Illuviation
Topic: Geomorphic Processes: Weathering, Mass Movement, Erosion and Soil Formation · NCERT: Class 11, Ch 5 "Geomorphic Processes"
Meaning
Illuviation is the deposit of washed-down material in the lower layers of soil. Water seeping down picks up clay, iron, aluminium, humus or calcium carbonate from the upper layers. It drops them deeper down. Over time this builds a zone of accumulation in the subsoil, usually the B horizon. This layer may become dense and clay-rich, or harden into nodules.
Example
In the older alluvium (bhangar) of the Ganga plains, lime carried down by water collects in the subsoil. It forms hard calcium carbonate nodules called kanker.
Don't confuse with
- Eluviation: illuviation is where material collects. Eluviation is where it is removed from, higher up in the soil.
- Leaching: leaching carries soluble minerals right out of the soil. Illuviation keeps the material inside the soil, just in a lower layer.
Related concepts
- Soil-forming factors
- Parent material
- Residual and transported soils
- Climate as a soil-forming factor
- Eluviation
- Desilication
- Humus
- Peat