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Earth Science Unit 1.4: Weathering and Soils

Earth Science Unit 1.4: Weathering and Soils. The Rock Cycle. Weathering The breakdown of rock near the surface due to surface processes, such as:. Chemical Alteration Solution & leaching of water Biological action Hydration Mechanical Impact

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Earth Science Unit 1.4: Weathering and Soils

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  1. Earth Science Unit 1.4:Weathering and Soils

  2. The Rock Cycle

  3. WeatheringThe breakdown of rock near the surface due to surface processes, such as: Chemical Alteration • Solution & leaching of water • Biological action • Hydration Mechanical • Impact • Wedging: Frost, Plant Roots, Salt Crystal Growth, Expansion of Hydrated Minerals

  4. Weathering Rates

  5. Differential Weathering and Erosion

  6. Differential Weathering and Erosion

  7. Mass-WastingMovement of Large Amounts of Material Downhill under Gravity • Creep • Mudflows • Slump • Rockfalls • Avalanches

  8. Surface Area and Weathering

  9. Spheroidal Weathering

  10. Spheroidal Weathering and Exfoliation

  11. Spheroidal Weathering

  12. Joints and Spheroidal Weathering

  13. What Determines Soil Type • Climate • Vegetation • Drainage • Time • Parent Material • Residual - Transported • Least Important Factor for Mature Soils

  14. Soil Formation Processes Leaching from Surface • K, Mg, Na • Ca • Si • Al, Fe Accumulation beneath Surface • Al, Fe in Humid Climates • Ca in Arid Climates

  15. Soil Horizons and Profiles Soil Horizons • Layers in Soil • Not Deposited, but Zones of Chemical Action Soil Profile • Suite of Layers at a Given Locality

  16. Principal Soil Horizons • O - Organic (Humus) Often Absent • A – Leaching (Clay Removed) • E - Bleached Zone - Only in Certain Soils • B – Accumulation • Absent in Young Soils • Distinct in Old Soils • Al, Fe, Clay (Moist) • Si, Ca (Arid) • C - Parent Material (bedrock)

  17. This may be the most difficult classification problem in science because of the many factors involved. Varied Bases for Classification Parent Material Special Constituent Materials Maturity Structure Climate & Vegetation Multiple Objectives Scientific Genesis & Evolution Agricultural Fertility Most Effective Use Engineering Slope Stability Expansion and Shrinkage Stability of Excavations Soil Classification

  18. "The 7th Approximation" • U.S. Soil Conservation Service • 12 Soil Orders

  19. "The 7th Approximation"

  20. Soils of the U.S.

  21. Typical Soil Profile (Spodosol)

  22. Aridisol, Kuwait

  23. Ultisols:AlabamaTennessee

  24. Oxisol, California (a Paleosol)

  25. Paleosol, Scotland

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