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OUTLINE

OUTLINE. Introduction Mechanical Weathering Chemical Weathering—Decomposition of Earth Materials Rates of Chemical Weathering Industrialization and Acid Rain Soil Composition The Soil Profile Factors in Soil Formation Soil Degradation Weathering and Natural Resources Geo-Recap.

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OUTLINE

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  1. OUTLINE • Introduction • Mechanical Weathering • Chemical Weathering—Decomposition of Earth Materials • Rates of Chemical Weathering • Industrialization and Acid Rain • Soil Composition • The Soil Profile • Factors in Soil Formation • Soil Degradation • Weathering and Natural Resources • Geo-Recap

  2. OBJECTIVES 1 Weathering brings about physical and chemical changes in Earth materials, whereas erosion removes weathered materials from their place of origin. 2 Mechanical weathering processes account for physical changes in Earth materials but do not change their composition. 3 In chemical weathering, compositional changes in Earth materials take place in response to chemical processes. 4 Changes resulting from weathering are easily recognized, and weathering brings about changes in human made rocklike materials. 5 Weathering yields the raw materials for both soils and sedimentary rocks. 6 Different types of soils form in response to weathering under specific circumstances. 7 A variety of factors are important in determining each type of soil and its fertility. 8 Erosion as well as physical and chemical deterioration of soils causes many problems, especially decreased productivity. 9 Physical and chemical changes in Earth materials are important in the origin and concentration of some mineral resources.

  3. Fig. 6-CO, p. 122

  4. Fig. 6-1, p. 124

  5. Fig. 6-2, p. 124

  6. Fig. 6-3, p. 125

  7. Fig. 6-4, p. 126

  8. Fig. 6-4a, p. 126

  9. Fig. 6-4b, p. 126

  10. Fig. 6-5, p. 126

  11. Fig. 6-6, p. 127

  12. Fig. 6-6b, p. 127

  13. Fig. 6-7a, p. 128

  14. Fig. 6-7b, p. 128

  15. Figure 1, p. 130

  16. Table 6-1, p. 130

  17. Figure 2, p. 131

  18. Fig. 6-8a, p. 132

  19. Fig. 6-8b, p. 132

  20. Fig. 6-9, p. 132

  21. Fig. 6-10, p. 133

  22. Fig. 6-10a-c, p. 133

  23. Fig. 6-10d, p. 133

  24. Fig. 6-11a, p. 134

  25. Fig. 6-11b, p. 134

  26. Fig. 6-12, p. 135

  27. Fig. 6-13, p. 135

  28. Fig. 6-14, p. 138

  29. Fig. 6-14a, p. 138

  30. Fig. 6-15, p. 139

  31. Fig. 6-15a, p. 139

  32. Fig. 6-15b, p. 139

  33. Table 6-2, p. 139

  34. SUMMARY • Mechanical and chemical weathering disintegrate and decompose parent material so that it is more nearly in equilibrium with new physical and chemical conditions. The products of weathering include solid particles, soluble compounds, and ions in solution. • The residue of weathering can be further modified to form soil, or it can be deposited as sediment, which may become sedimentary rock. • Mechanical weathering processes include frost action, pressure release, thermal expansion and contraction, and the activities of organisms. Particles liberated by mechanical weathering retain the chemical composition of the parent material. • Chemical weathering processes such as solution, oxidation, and hydrolysis result in a chemical change of the weathered products. Clay minerals, various ions in solution, and soluble compounds form during chemical weathering. • Chemical weathering proceeds most rapidly in hot, wet environments, but it takes place in all areas. • Mechanical weathering aids chemical weathering by breaking parent material into smaller pieces, thereby exposing more surface area.

  35. SUMMARY • Weathering can and does alter building stones and other human-made materials exposed to the elements. • Mechanical and chemical weathering produce regolith, some of which is soil if it consists of solids, air, water, and humus and supports plants. • Soils are characterized by horizons that are designated, in descending order as O, A, B, and C; soil horizons differ in texture, structure, composition, and color. • The factors that control soil formation include climate, parent material, organic activity, relief and slope, and time. • Soils called pedalfers develop in humid regions, whereas arid and semiarid regions’ soils are pedocals, many of which contain irregular masses of caliche in horizon B. • Laterite is a soil that results from intense chemical weathering in the tropics. These deep, red soils are sources of aluminum ores if derived from aluminum- rich parent material. • Soil degradation is a problem in some areas. Human practices such as construction, agriculture, and deforestation can accelerate soil degradation.

  36. Intense chemical weathering is responsible for the origin of residual concentrations, many of which contain valuable minerals such as iron, lead, copper, and clay.

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