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  • Insert cover image for Chapter 12 (p. 320).
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  • 12

    1. 1. Chapter 12: Soils and Soil Development Physical Geography Ninth Edition Robert E. Gabler James. F. Petersen L. Michael Trapasso Dorothy Sack
    2. 2. Soils <ul><li>Soil: dynamic natural body capable of supporting a vegetative cover </li></ul><ul><li>It contains chemical solutions, gases, organic refuse, flora, and fauna </li></ul>
    3. 3. Soils <ul><li>Soil integrates: </li></ul><ul><ul><li>Atmosphere </li></ul></ul><ul><ul><li>Hydrosphere </li></ul></ul><ul><ul><li>Lithologic </li></ul></ul><ul><ul><li>Biotic </li></ul></ul><ul><li>Soil is home to organisms, forming environments in which they live </li></ul>
    4. 4. 12.1 Major Soil Components <ul><li>Four major components of Soil: </li></ul><ul><ul><li>Inorganic materials </li></ul></ul><ul><ul><li>Soil water </li></ul></ul><ul><ul><li>Soil air </li></ul></ul><ul><ul><li>Organic matter </li></ul></ul><ul><li>Interaction and proportion of each are important factors </li></ul>
    5. 5. 12.1 Major Soil Components <ul><li>Inorganic Materials </li></ul><ul><ul><li>Insoluble materials </li></ul></ul><ul><ul><li>Rock fragments and minerals that will not readily dissolve in water </li></ul></ul><ul><ul><li>Chemical composition of soil result from: </li></ul></ul><ul><ul><ul><li>Weathering </li></ul></ul></ul><ul><ul><ul><li>Old deposits </li></ul></ul></ul><ul><ul><ul><li>Dissolved minerals </li></ul></ul></ul><ul><ul><li>Soil Fertilization </li></ul></ul>
    6. 6. 12.1 Major Soil Components <ul><li>Soil Water </li></ul><ul><ul><li>Original source is precipitation </li></ul></ul><ul><ul><li>Open system </li></ul></ul><ul><ul><li>Capillary water </li></ul></ul><ul><ul><li>Hygroscopic water </li></ul></ul><ul><ul><li>Gravitational water </li></ul></ul><ul><ul><li>Eluviation </li></ul></ul><ul><ul><li>Illuviation </li></ul></ul><ul><ul><li>Hardpan </li></ul></ul><ul><ul><li>Stratification </li></ul></ul>
    7. 7. 12.1 Major Soil Components <ul><li>Q: What are some examples of energy and matter that flow into and out of the soil system? </li></ul>
    8. 8. 12.1 Major Soil Components <ul><li>Q: How does deposition by capillary water differ from deposition (illuviation) by gravitational water? </li></ul>
    9. 9. 12.1 Major Soil Components <ul><li>Soil Air </li></ul><ul><ul><li>As much as 50% of soil may consist of spaces between soil particles and clumps </li></ul></ul><ul><ul><li>Supplies microorganisms with oxygen and carbon dioxide </li></ul></ul><ul><li>Organic Matter </li></ul><ul><ul><li>Humus: decayed remains of plant and animal material </li></ul></ul><ul><ul><li>Humus supplies nutrients and minerals to soil </li></ul></ul>
    10. 10. 12.2 Characteristics of Soil <ul><li>Readily Testable properties: </li></ul><ul><ul><li>Color </li></ul></ul><ul><ul><li>Texture </li></ul></ul><ul><ul><li>Structure </li></ul></ul><ul><ul><li>Acidity </li></ul></ul><ul><ul><li>Alkalinity </li></ul></ul><ul><ul><li>Capacity to hold and transmit water </li></ul></ul>
    11. 11. 12.2 Characteristics of Soil <ul><li>Color </li></ul><ul><ul><li>Red or yellow (iron) </li></ul></ul><ul><ul><li>Black (decomposed) </li></ul></ul><ul><li>Texture </li></ul><ul><ul><li>Soil texture: particle size </li></ul></ul><ul><ul><li>Clay (< 0.002 mm) </li></ul></ul><ul><ul><li>Silty (0.002 to 0.05 mm) </li></ul></ul><ul><ul><li>Sandy (0.05 to 2.0 mm) </li></ul></ul><ul><ul><li>Rocks (> 2.0 mm) </li></ul></ul>
    12. 12. 12.2 Characteristics of Soil <ul><li>Texture and proportion of particle size </li></ul><ul><ul><li>Soil grade (% sand, silt, and clay) </li></ul></ul><ul><ul><li>Loams </li></ul></ul><ul><ul><li>Soils with a higher proportion of large particles tend to be well aerated and allow for infiltration </li></ul></ul>
    13. 13. 12.2 Characteristics of Soil <ul><li>Structure </li></ul><ul><ul><li>Soil peds </li></ul></ul><ul><ul><li>Porosity </li></ul></ul><ul><ul><li>Permeability </li></ul></ul><ul><ul><li>Classified by form: </li></ul></ul><ul><ul><ul><li>Columns </li></ul></ul></ul><ul><ul><ul><li>Prisms </li></ul></ul></ul><ul><ul><ul><li>Angular blocks </li></ul></ul></ul><ul><ul><ul><li>Nutlike spheroids </li></ul></ul></ul><ul><ul><ul><li>Laminated plates </li></ul></ul></ul><ul><ul><ul><li>Crumbs </li></ul></ul></ul><ul><ul><ul><li>Granules </li></ul></ul></ul>
    14. 14. 12.2 Characteristics of Soil <ul><li>Acidity and Alkalinity </li></ul><ul><ul><li>pH scale (0-14) </li></ul></ul><ul><ul><li>Lower pH (higher acidity) </li></ul></ul><ul><ul><li>Higher pH (alkaline conditions) </li></ul></ul><ul><ul><li>Soil acidity or alkalinity helps determine available nutrients </li></ul></ul>
    15. 15. 12.2 Characteristics of Soil <ul><li>Acidity and Alkalinity </li></ul><ul><ul><li>Optimum pH varies by plant species </li></ul></ul><ul><ul><li>Leaching </li></ul></ul><ul><ul><li>Soils in the east tend to be acidic </li></ul></ul><ul><ul><li>Soils in the west tend to be alkaline </li></ul></ul>
    16. 16. 12.3 Development of Soil Horizons <ul><li>Parent material </li></ul><ul><li>Soil profiles show: </li></ul><ul><ul><li>Color </li></ul></ul><ul><ul><li>Structure </li></ul></ul><ul><ul><li>Composition </li></ul></ul><ul><ul><li>Other characteristics with depth </li></ul></ul>
    17. 17. 12.3 Development of Soil Horizons <ul><li>Soil Horizons: </li></ul><ul><ul><li>Distinct layers distinguished by their physical and chemical properties </li></ul></ul><ul><ul><li>Designated by set of letters that refer to: </li></ul></ul><ul><ul><ul><li>Composition </li></ul></ul></ul><ul><ul><ul><li>Dominant process </li></ul></ul></ul><ul><ul><ul><li>Position in the soil profile </li></ul></ul></ul>
    18. 18. 12.3 Development of Soil Horizons <ul><li>Soil Horizons: </li></ul><ul><ul><li>O horizon </li></ul></ul><ul><ul><li>A horizon </li></ul></ul><ul><ul><li>E horizon </li></ul></ul><ul><ul><li>B horizon </li></ul></ul><ul><ul><li>C horizon </li></ul></ul><ul><ul><li>R horizon </li></ul></ul>
    19. 19. 12.4 Factors Affecting Soil Formation <ul><li>Weathering </li></ul><ul><li>Chemical reactions </li></ul><ul><li>Physical Processes </li></ul><ul><li>Soil development is a function of: </li></ul><ul><ul><li>Climate (Cl) </li></ul></ul><ul><ul><li>Organic matter (O) </li></ul></ul><ul><ul><li>Relief (R) </li></ul></ul><ul><ul><li>Parent material (P) </li></ul></ul><ul><ul><li>Time (T) </li></ul></ul>
    20. 20. 12.4 Factors Affecting Soil Formation <ul><li>Parent Material </li></ul><ul><ul><li>Residual parent material (e.g. physical or chemical breakdown) </li></ul></ul><ul><ul><li>Transported parent material (e.g. carried by water, wind, etc.) </li></ul></ul><ul><ul><li>Sandstone </li></ul></ul><ul><ul><li>Chemicals & nutrients reflect composition </li></ul></ul>
    21. 21. 12.4 Factors Affecting Soil Formation <ul><li>Organic Material </li></ul><ul><ul><li>Plant die and decompose </li></ul></ul><ul><ul><li>Leaves fall to the ground </li></ul></ul><ul><ul><li>Most fertile soil are typically grasslands </li></ul></ul><ul><ul><li>Microorganisms (e.g. bacteria) </li></ul></ul><ul><ul><li>Earthworms, ants… </li></ul></ul>
    22. 22. 12.4 Factors Affecting Soil Formation <ul><li>Climate </li></ul><ul><ul><li>Global vs. Local scale </li></ul></ul><ul><ul><li>Equatorial: </li></ul></ul><ul><ul><ul><li>Higher temps increase soil microorganisms, preclude thick accumulations of humus </li></ul></ul></ul><ul><ul><li>Middle Latitudes: </li></ul></ul><ul><ul><ul><li>Cooler temps slow decay and produce rich humus </li></ul></ul></ul><ul><ul><li>Polar Latitudes </li></ul></ul><ul><ul><ul><li>Cold temperatures and limited plant growth result in thin humus </li></ul></ul></ul>
    23. 23. 12.4 Factors Affecting Soil Formation <ul><li>Climate, Temperature, and organic material </li></ul><ul><ul><li>Q: What range of mean annual temperature is most favorable for the accumulation of humans? </li></ul></ul>
    24. 24. 12.4 Factors Affecting Soil Formation <ul><li>Climate </li></ul><ul><ul><li>Moisture Conditions </li></ul></ul><ul><ul><ul><li>Ample precipitation supports plant growth which increases organic content </li></ul></ul></ul><ul><ul><ul><li>Too much precipitation will cause leaching </li></ul></ul></ul><ul><ul><li>Evaporation rate </li></ul></ul>
    25. 25. 12.4 Factors Affecting Soil Formation <ul><li>Land Surface Configuration </li></ul><ul><ul><li>Slope </li></ul></ul><ul><ul><li>Aspect (direction of its faces) </li></ul></ul><ul><li>Time </li></ul><ul><ul><li>Young & mature soils </li></ul></ul><ul><ul><li>Alluvium </li></ul></ul>
    26. 26. 12.5 Soil-Forming Regimes <ul><li>Self-forming regimes: vary mainly due to climate and vegetation </li></ul><ul><li>Climate differences produce 3 primary soil-forming regimes: </li></ul><ul><ul><li>Laterization </li></ul></ul><ul><ul><li>Podzolization </li></ul></ul><ul><ul><li>Calcification </li></ul></ul>
    27. 27. 12.5 Soil-Forming Regimes <ul><li>Laterization </li></ul><ul><ul><li>Humid and subtropical climates </li></ul></ul><ul><ul><li>Result of high temp and abundant precip. </li></ul></ul><ul><ul><li>Laterite: soil type (brick-like) </li></ul></ul><ul><ul><li>No O horizon, absence of organic acids </li></ul></ul><ul><ul><li>Topsoil reddish </li></ul></ul>
    28. 28. 12.5 Soil-Forming Regimes <ul><li>Podzolization </li></ul><ul><ul><li>High middle latitudes </li></ul></ul><ul><ul><li>Moist with short, cool summers and severe winters </li></ul></ul><ul><ul><li>Podzol </li></ul></ul><ul><ul><li>East Coast of U.S. </li></ul></ul>
    29. 29. 12.5 Soil-Forming Regimes <ul><li>Calcification </li></ul><ul><ul><li>Evapotranspiration exceeds precipitation </li></ul></ul><ul><ul><li>Often thick calcium carbonate (alkali dusts) </li></ul></ul><ul><ul><li>Deserts of American west </li></ul></ul>
    30. 30. 12.5 Soil-Forming Regimes <ul><li>Regimes of Local Importance </li></ul><ul><ul><li>Salinization: concentration of salts </li></ul></ul><ul><ul><li>Occurs most often: </li></ul></ul><ul><ul><ul><li>in dry areas </li></ul></ul></ul><ul><ul><ul><li>Intensive irrigation </li></ul></ul></ul><ul><ul><li>Gleization: poorly drained soils in cold, wet climates </li></ul></ul>
    31. 31. 12.6 Soil Classification <ul><li>Soil Taxonomy </li></ul><ul><ul><li>Soil classification system that is based on their characteristics </li></ul></ul><ul><ul><li>Natural Resources Conservation Service (NRCS) </li></ul></ul><ul><ul><li>Mapped by their spatial distribution </li></ul></ul><ul><li>Soil Surveys </li></ul><ul><ul><li>Books that outline and describe soils in a region </li></ul></ul><ul><ul><li>Useful for factors such as fertility, irrigation, & drainage </li></ul></ul>
    32. 32. 12.6 Soil Classification <ul><li>NRCS Soil Classification System </li></ul><ul><ul><li>Based on development and composition </li></ul></ul><ul><ul><li>Soil order: largest division </li></ul></ul><ul><ul><li>Subdivisions </li></ul></ul><ul><ul><li>Horizons below the surface: </li></ul></ul><ul><ul><ul><li>Subsurface horizon </li></ul></ul></ul><ul><ul><ul><li>Epipedons </li></ul></ul></ul>
    33. 33. 12.6 Soil Classification <ul><li>Common Soil Horizons (NRCS Soil System) </li></ul>
    34. 34. 12.6 Soil Classification <ul><li>NRCS Soil Orders: based on a variety of characteristics and processes </li></ul>
    35. 35. 12.6 Soil Classification <ul><li>Map of dominant soil orders in U.S. </li></ul>
    36. 36. 12.6 Soil Classification <ul><li>World Map of dominant soil orders (NRCS system) </li></ul>
    37. 37. 12.6 Soil Classification <ul><li>World Map of dominant soil orders (NRCS system) </li></ul>
    38. 38. 12.6 Soil Classification <ul><ul><li>Entisols </li></ul></ul><ul><ul><li>Inceptisols </li></ul></ul><ul><ul><li>Histosols </li></ul></ul><ul><ul><li>Andisols </li></ul></ul><ul><ul><li>Gelisols </li></ul></ul><ul><ul><li>Aridisols </li></ul></ul>
    39. 39. 12.6 Soil Classification <ul><ul><li>Vertisols </li></ul></ul><ul><ul><li>Mollisols </li></ul></ul><ul><ul><li>Alfisols </li></ul></ul><ul><ul><li>Spodosols </li></ul></ul><ul><ul><li>Ultisols </li></ul></ul><ul><ul><li>Oxisols </li></ul></ul>
    40. 40. 12.7 Soil as a Critical Natural Resource <ul><li>Soil Fertility </li></ul><ul><li>Q: What could have been done to prevent the kind of soil loss shown in this example? </li></ul><ul><li>Q: What other soil conservation practices are often used to preserve the soil resource? </li></ul>
    41. 41. Physical Geography End of Chapter 12: Soils and Soil Development
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