Leaching
Topic: Geomorphic Processes: Weathering, Mass Movement, Erosion and Soil Formation · NCERT: Class 11, Ch 5 "Geomorphic Processes"
Meaning
Leaching is the removal of soluble minerals from rock or soil by water seeping downwards. In wet tropical areas with heavy rain, it washes out bases such as calcium, sodium, magnesium and potassium. It also removes most of the silica. Iron and aluminium oxides do not dissolve easily, so they are left behind. This builds up laterite soil and, where aluminium is rich, bauxite, the ore of aluminium. So leaching makes soil poorer but concentrates useful ores.
Example
The bauxite deposits of Panchpatmali in Koraput district, Odisha, formed when heavy rain leached minerals from the rock. Aluminium oxide was left behind.
Don't confuse with
- Eluviation: it moves material down within the soil, and that material is deposited in a lower layer (illuviation). Leaching carries the dissolved minerals out of the soil altogether.