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SAI TEJA.P 1st B.sc MPG Weathering of rocks is constant and it destroy the rocks. weathering is the breaking down of rocks , soils and minerals weathering produces rocks waste are transported are called EROSION Weathering is of two types 1)Mechanical (or) Physical weathering 2)Chemical weathering In this type of weathering the rocks are break and disintegrate They loose broken material will be angular in shape In mechanical (or) physical weathering is three types:a)Thermal Weathering b)Exfoliation c)Frost Action Thermal weathering is by a sudden breaking rocks by temperature changes More common in diserts areas because temperature changes rapidly And also forest fires and lightning will weathering the rocks Rocks breaking along the joints .The joints are breaking will be parallel to the surface. Slowly rocks will fall down layers by layers. This will produce large dome like structure called EXFOLIATION DOMES. Rocks and boulders will show rounded form called SPHEROIDAL WEATHERING. Exfoliation joints have modified the nearsurface portions of massive granitic rocks in Yosemite National Park Exfoliation joints in granite at Enchanted Rock State Natural Area, Texas, USA River water enters the cracks and joints of the rocks. This water will freeze during the night. Frozen water will create pressure and temperature and increase the cracks. Frost action is common in high areas (Hill stations & Gardens) exposed to rain and snow. A rock in Abisko, Sweden fractured by mechanical frost weathering or thermal stress Chemical weathering is done by rain water. Chemical weathering will decompose and form solutions. Chemical weathering changes the chemical composition of the mineral. EX:-Felspar mineral changes to clay mineral. It depends on composition of original material and depth of the mineral. This weathering is by the process of SOLUTIONS, OXIDATION, HYDRATION, AND FORMATION OF CARBONATES. Comparison of unweathered (left) and weathered limestone. (right) River water will have carbon-dioxide which reacts with minerals. EX:-CALCIUM MINERALS & IRON OXIDE etc…, Carbonates changes into bi-carbonates. solutions will fall down. It is the chemical composition with oxygen. Water having oxygen will react with iron minerals. Solutions are formed and FERROUS IRON changes into FERRIC IRON. Hydration is the chemical reaction with water. Water removes soluble material by LEACHING. Some chemical reactions form HYDROUS OXIDE & HYDROUS SILICATES. Water reaction will bring another change called HYDROLYSIS Erosional features formed due to weathering. Atmospheric conditions like temperature, wind directions, rain water will form different features. They are bad lands, cuestas, misas, buttes, hogbacks etc.., End product of weathering is soils. There are different types of soils LATERITIC SOIL, SANDY SOIL, BLACK COTTON SOIL, LOAMY SOIL, CLAYEY SOIL, PEAT SOIL etc…, Lateritic soil, Black soil, Peat soil are good for agriculture. Loamy soil and sandy soil are not good for agriculture. Mr . P.C. Swaroop sir Department of Geology