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Ch. 7 Sec. 1

Ch. 7 Sec. 1. Weathering. Weathering. Weathering Process by which rocks on or near Earth’s surface break down and change Erosion Removal and transport of weathered material. Mechanical Weathering. Physical breakdown (size, shape) of rock Temperature

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Ch. 7 Sec. 1

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  1. Ch. 7 Sec. 1 Weathering

  2. Weathering • Weathering • Process by which rocks on or near Earth’s surface break down and change • Erosion • Removal and transport of weathered material

  3. Mechanical Weathering • Physical breakdown (size, shape) of rock • Temperature • Expanding and Freezing of water in cracks: Frost Wedging

  4. Mechanical Weathering • Physical breakdown • Pressure • The pressure is causing outer rock layers to be stripped away: Exfoliation

  5. Chemical Weathering • Changes in the Composition of the rock • Agents of chemical weathering…. • Water, oxygen, carbon dioxide, and acids • Temperature influences the rate of chemical weathering • Water • Dissolves many minerals • Hydrolysis: decomposition of silicate minerals

  6. Chemical Weathering • Oxygen • Oxidation: chemical reaction of oxygen with other substances • Abundant in the atmosphere • Iron in some rocks can react forming new rocks • Pyrite • Magnitite

  7. Chemical Weathering • Carbon dioxide (CO2) • Produced by living organisms respiration • CO2 with water produces carbonic acid • The process of the carbonic acid reacting with minerals results in the formation of clay minerals

  8. Chemical Weathering • Acid Precipitation • From burning of fossil fuels • Forms Sulfuric and Nitric acids • Describe the solutions by the pH scale. The lower the number, the more acidic

  9. Rate of Weathering • Rate of weathering occurs slowly, but some interactions can accelerate the process • Climate  affects both chemical and physical • Chemical weathering (high) • Precipitation, temperature, & evaporation • High temps and rainfall speed up chemical weathering • Physical weathering • Cool and dry conditions (water freezes and thaws)

  10. Rate of Weathering • Rock Type and Composition • Hardness and surface area helps decrease weathering • Sedimentary rocks weather more easily than igneous and metamorphic

  11. Rate of Weathering • Surface Area • Mechanical weathering breaks up rocks into smaller pieces • As pieces get smaller, their surface area increases • And surface area increases, the more weathering occurs

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