3、坡地地貌.ppt.Convertor（3. Slope geomorphology）.docVIP

3、坡地地貌.ppt.Convertor（3. Slope geomorphology） Chapter iii weathering and gravity landform and accumulation One. Weathering and debris The exposed rocks are broken and decomposed by solar radiation, temperature changes, water and biology, forming various cuttings, sand grains, and clay. This effect is called weathering. Physical weathering chemical weathering biological differentiation (1) type of weathering 1. Physical weathering Concept: mechanical disintegration of surface rock due to temperature change and the freezing and thawing of water in pores and the crystallization of rock. It causes the rock to change from a relatively intact state to a loose and broken state, which increases the porosity and surface area of the rock. This weathering effect that only causes rocks physical change is known as physical weathering or mechanical weathering. Main ways of physical weathering: (1) temperature-weathering: the periodic changes in the surface temperature of the rock cause the rocks to disintegrate, which occurs in the arid and semi-arid regions where the temperature difference is large. (2) ice cleavage: the water in the rock fracture expands after freezing, becomes smaller after melting, then adds water, and then expands again, which can cause rock fracture in the long term. It mainly happens in high latitudes and high mountains. (3) crystallization and deliquescence of salt: similar to ice, the crystallization of salts increases the volume, which occurs in arid and semi-arid regions. 2. Chemical weathering Concept: chemical weathering is refers to the rock in the water, oxygen and carbon dioxide in the air and water solution under the action of what had happened, hydration, hydrolysis, the dissolution of carbonate and oxidation, and a series of complex chemical changes. It causes the soluble minerals in the rock to gradually dissolve or sink into the lower layer of the weathering crust, and may be redeposited in a new environment. The type of chemical weathering (1