Rates of weathering   lesson 6
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  • 1. Lesson 6
  • 2. Rates of weathering The speed at which rock are broken down.This depends on several factors:  Climate  Rock Characterics  Vegetation
  • 3. CLIMATE Chemical Weathering Physical Weathering Most intense in hot and wet  Particularly active in climate cold climates where Chemical reactions frost shattering promotes by high dominates temperatures Heavy rainfall provides  Also active in desert necessary moisture for the climates where processes insolation weathering or exfoliation dominates E.g: Deep weathering profile and typical red soil in tropical climate reflect active oxidation
  • 4. Climatic conditions 1. Strong Chemical Weathering – Hot and wet  Temperature: 70C – 300C  Rainfall : 1600 – 2500mm 2. Weak Chemical Weathering  Temperature: -30C to -200C  Rainfall : 0 – 900mm 3. Strong Physical Weathering  Temperature: -50C to -100C  Rainfall : 300 mm to 1300mm 4. Weak Physical Weathering  Temperature: 00C to 90C  Rainfall : 0 – 1700mm
  • 5. Rock Characteristics Define the term joints and bedding planes. Joints – fractures or cracks that run through rocks Bedding planes – the junctions between beds of sedimentary rocks
  • 6. Permeability and porosity Which of the following texture is easily weathered?
  • 7. Vegetation Presence of vegetation promotes weathering Organic acids speed up hydrolysis Moss cling to rock surface, holding water against them like a wet sponge  encourage chemical weathering At the same time protect a rock surface from temperature extreme which reduce physical weathering