Desilication
Topic: Geomorphic Processes: Weathering, Mass Movement, Erosion and Soil Formation · NCERT: Class 11, Ch 5 "Geomorphic Processes"
Meaning
Desilication is the removal of silica from soil by heavy leaching. Leaching means minerals being dissolved and washed downwards by water seeping through the soil. It happens in hot, wet equatorial and tropical climates with heavy rainfall. Along with most of the silica, bases such as calcium, sodium, magnesium and potassium are also washed out. What stays behind are iron and aluminium oxides, which give the soil its red colour and make it hard when dry. This is how laterite forms. Where aluminium is concentrated enough, it forms bauxite, the ore of aluminium.
Example
Laterite soils on the high-rainfall Western Ghats of Kerala and Karnataka form through desilication. In Odisha, the same process has left rich bauxite deposits at Panchpatmali.
Don't confuse with
- Leaching: the general washing out of soluble minerals by water. Desilication is the specific loss of silica under heavy tropical leaching.
- Eluviation: the washing down of material from upper soil layers, which is then laid down lower in the soil (illuviation). Desilication removes silica from the soil profile almost entirely.
Related concepts
- Soil-forming factors
- Parent material
- Residual and transported soils
- Climate as a soil-forming factor
- Eluviation
- Illuviation
- Humus
- Peat