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Earth’s External Processes

Earth’s External Processes. Weathering – the disintegration and decomposition of material at or near the surface Mass wasting – the transfer of rock material downslope under the influence of gravity

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Earth’s External Processes

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  1. Earth’s External Processes • Weathering – the disintegration and decomposition of material at or near the surface • Mass wasting – the transfer of rock material downslope under the influence of gravity • Erosion – the incorporation and transportation of material by a mobile agent, usually water, wind, or ice

  2. Weathering • Two kinds of weathering • Mechanical weathering • Breaking of rocks into smaller pieces • Chemical weathering • Chemical transformation of rock into one or more new compounds

  3. Increase in Surface Area by Mechanical Weathering

  4. Mechanical Weathering • Four important processes • Frost wedging – expansion of freezing water • Salt crystal growth • Sheeting – generates onion-like layers and exfoliation domes • Biological activity

  5. Frost Wedging

  6. Sheeting and Exfoliation of Igneous Rocks

  7. Chemical Weathering • Alters the internal structures of minerals by removing or adding elements • Most important agent is water • Oxygen dissolved in water oxidizes materials • Carbon dioxide (CO2) dissolved in water forms carbonic acid and alters the material

  8. Chemical Weathering • Spheroidal Weathering • Generates rounded rocks • Weathering works inward from exposed surfaces

  9. Rock Type Influences Weathering

  10. Rates of Weathering • Important factors • Climate • Temperature and moisture are the most crucial factors • Chemical weathering is most effective in areas of warm temperatures and abundant moisture

  11. Rates of Weathering • Differential weathering • Caused by variations in composition • Creates unusual and spectacular rock formations and landforms

  12. Soil • An interface in the Earth system • Soil is a combination of mineral matter, water, and air • Regolith • Rock and mineral fragments • Supports the growth of plants

  13. Soil Components

  14. Soil • Soil texture and structure • Texture refers to the proportions of different particle sizes • Sand (large size) • Silt • Clay (small size) • Loam (a mixture of all three sizes) is best suited for plant life

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