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SOIL FORMATION

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Explore the intricate process of soil formation, influenced by climate, organisms, relief, parent material, and time. Discover how weathering, physical and chemical processes shape soil properties and compositions.

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SOIL FORMATION

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  1. SOIL FORMATION Soil forms when weathered parent material interacts with environment.

  2. weathering • Wearing parent material down • PHYSICALLY • CHEMICALLY

  3. Physical (Mechanical): disintegration of parent material into smaller pieces increases surface area: surface area increases by about the same factor as particle size decreases.

  4. Chemical (Biogeochemical) acts on surfaces: primary minerals are broken down and secondary minerals are formed.

  5. Soil forms when weathered parent material interacts with the environment. What would constitute the ENVIRONMENT of a soil?

  6. Soil carbonic acid (formed from LIFE in soil) extracts minerals from soil(which came from parent material)

  7. How fast does soil form? Slow--------------------------------------Fast ~ 1 cm/1000 yr ~ 30cm/50yr Not very.

  8. Hans Jenny • 1941: soil is open system, properties are functionally related; system changes when property(ies) change(s). • Jenny’s CLORPT equation s = ƒ (cl, o, r, p, t) He expanded on the ideas of Dokuchaev

  9. 1. CLIMATE 2. ORGANISMS 3. RELIEF 4. PARENT MATERIAL 5. TIME

  10. 1. CLIMATE …determines speed, character of soil development: determines the type and rate of weathering determines living organisms and plants found in an area

  11. components of climate : • 1. Temperature • -for every 10°C , biochemical rxn rates 2X • 2. Effective precipitation • (water that moves through entire soil column, including regolith) • -depth of water = depth of weathering • -water moves soluble & suspended materials

  12. (Fig. 2.15) High temperatu

  13. Temperature and humidity increase the depth of weathering. Humid, tropics High latitude Dry, SW US Humid, SE US

  14. Effective precipitation -a) seasonal distribution -b) temperature, evaporation -c) topography -d)permeability

  15. a) Seasonal distribution of precipitation: Location B 600 mm/yr Location A 600 mm/yr 100mm 50mm 6 rainy months only Every month

  16. b) Temperature and evaporation: Location A hot Location B cool High evapotranspiration Low evapotranspiration 600 mm 600 mm Lower effective ppt Higher effective ppt

  17. Topography: concave or bottom of slope (receiving) level slope

  18. Permeability:

  19. 2. Organismsplant and animal (Living plants and animals on and in soil) -sources of organic matter -nutrient recycling -vegetation prevents erosion -type of vegetation influences soil type -base pumping -

  20. Type of vegetation influences soil type

  21. Base pumping Deciduous trees are more effective base pumpers than conifers . -needles are hard to break down -basic cations leach away: soil is acidic -deciduous litter is easy to break down -cations (bases) are released so surface soils are not acidic

  22. Macroanimals (insects, mammals, gastropods, earthworms) • mix, bind soil; create channels for air, water

  23. crotovinas

  24. night crawlers and water

  25. Macroanimals (insects, mammals, gastropods, earthworms) • mix, bind soil; create channels for air, water • Microanimals (nematodes, protozoa)

  26. Macroanimals (insects, mammals, gastropods, earthworms) • mix, bind soil; create channels for air, water • Microanimals (nematodes, protozoa) • Macroplants (the green plants) • provide organic matter, roots create channels, adsorb nutrients, release CO2, stabilize, protect from erosion

  27. Macroanimals (insects, mammals, gastropods, earthworms) • mix, bind soil; create channels for air, water • Microanimals (nematodes, protozoa) • Macroplants (the green plants) • provide organic matter, roots create channels, adsorb nutrients, release CO2, stabilize, protect from erosion • Micro “plants” (fungi, bacteria, actinomycetes, algae) • decomposers

  28. 3. Relief/Topography • important for rate of runoff, erosion, drainage

  29. Flat valley floors and flat ridge tops: soil accumulates; (deepening>removal) Slopes: (removal> deepening)

  30. 4. Parent Material Determines: • texture, • types of weathering, • mineral make-up

  31. Some Physical Weathering Processes: 1. Freeze/thaw

  32. Freeze / Thaw

  33. Physical: 1. Freeze/thaw 2. Exfoliation

  34. 2. Exfoliation (unloading)

  35. Physical: 1. Freeze/thaw 2. Exfoliation 3. Abrasion

  36. 3. Abrasion (wind, water, ice) wind

  37. water

  38. ice

  39. Physical: 1. Freeze/thaw 2. Exfoliation 3. Abrasion 4. Salt wedging

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