lateritization

Lateritization is a tropical weathering process that forms laterite soils and duricrusts in hot, humid climates. Prolonged chemical weathering and intense leaching remove most soluble elements from rock, while oxides of iron and aluminum accumulate near the surface. The resulting materials tend to be red or yellow, and may develop a hard, cemented crust known as laterite or duricrust.

Causes and mechanism: High temperature and heavy rainfall accelerate chemical reactions and the dissolution of silica and bases such as calcium, potassium, and sodium. In the acidic tropical environment, leaching depletes nutrients from the upper soil profile, leaving iron and aluminum oxides behind. Over time these oxides can cement with clay minerals to form a dense, durable horizon that resists further weathering.

Profile and properties: Laterite soils may display a saprolite beneath a ferruginous crust. They are often strongly acidic and low in plant-available nutrients unless amended. The color ranges from brick red to orange or brown, driven by ferric oxide content. When crusts are consolidated, they can form durable, rock-like surfaces; when not, the material remains crumbly and less stable for agricultural use.

Distribution and uses: Lateritization is characteristic of tropical regions in Africa, South America, and Southeast Asia. Economically, laterites host nickel and aluminum ore deposits, and the rock itself has been used as building material and road base in several regions. Agricultural fertility is typically limited without soil management, drainage improvements, or amendments to increase nutrient availability.