Arid Zone: In arid regions where days are very hot and nights are cool, the rocks shatter mainly by the influence of unequal expansions and contraction. The soil thus produced contains the grain of minerals which are disintegrated from the original rock. The surface layers of such soil often become hard due to the crystallization of salts. The evaporation of water brings dissolved salts to the surface by capillary action which cements the upper layer of the soil. The lime crust is found in the desert soils of Texas, New Mexico and North Africa, while the gypsum crust occurs in Egypt and central Australia deserts.
Arctic Region: In arctic region the ice and frost activity take part in rock disintegration and produce a soil consisting of under-composed mineral and rock particles. The soil mantle, which is usually shallow, is characterized by abundant silt, peat, and water in a permanently frozen state.
Humid Climate: In humid temperate climate the rocks are weathered predominantly by a combination of both disintegration and decomposition. Here podzol type of soil is formed. This soil shows the characteristic development of soil profile having A, B and C horizons.
Tropical Climate: In tropical climate the chemical weathering plays an active role and rocks are weathered thoroughly upto a great depth. The most common soil of tropical areas is “laterite”, which develops as a result of weathering of silicate rocks. During weathering most of the silica is leached out and the insoluble hydroxides of rion and aluminium accumulate near the surface to give rise a reddish brown residual deposit. Laterite is a very useful construction material. When moist, it is soft and can be cut easily into bricks which become very hard on drying.
Temperate Climate: The soils of both the temperate and the tropical regions may develop “hard pan” at some depth below the surface. The downwardly moving rain water may bring leached silica from the upper horizons ot lower horizons where it is redeposited. It causes cementation of the soil layer. This type of hard, well cemented and impercious ayer of soil is called “hard pan”. Such hard pans present very useful horizon for the foundation of buildings and other structures.