1. Soil forms when weathered parent material interacts with environment.
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?
Not very.
Slow Fast
~ 1 cm/1000 yr ~ 30cm/50yr

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.
High latitude
Humid,
tropics
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

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

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

19. Permeability:

20. 2. Organisms plant 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 -

21. Type of vegetation influences soil type

22. 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

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

24. crotovinas

25. night crawlers and water

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

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

28. 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

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

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

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

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

35. Freeze / Thaw

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

41. 2. Exfoliation (unloading)

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

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

48. water

49. ice

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

51. 4. Salt Wedging

52. Physical: 1. Freeze/thaw 2. Exfoliation 3. Abrasion 4. Salt wedging
5. Root wedging

53. 5. Root Wedging

54. Chemical (biogeochemical):
1. Hydrolysis: minerals react with H2O
H+ replace soluble parts; OH- combine with mineral cations
2. Hydration: mineral combines with H2O
3. Oxidation: mineral combines with O2 (lose electron)
Reduction: loss of O2 (gain electron)
4. Carbonation: oxides combine with acids to make carbonates
5. Complexation: organic acids form organic complexes with metal cations

56. 5. Time
Amount of time soil has been exposed to weathering and soil forming processes influences soil properties.
Jenny’s staircase
Ohio/Ky.

59. 4 soil forming processes: (pedogenic)
Transformation

61. 4 soil forming processes:
Transformation
Translocation

63. 4 soil forming processes:
Transformation
Translocation
Addition

65. 4 soil forming processes:
Transformation
Translocation
Addition
Loss