1. Soils and the Environment

2. Learning Objectives Soils terminology & processes
Interaction of water in soil processes, soil fertility
Classification of soils (familiarity)
Engineering properties of soil
Relationships between land use and soils
Sediment pollution
Desertification

3. How/why is soil important in environmental geology?
What is soil? Definition(s)?
How does soil form?
How does chemical weathering work?
What is the significance of mechanical weathering?
Factors/parameters that affect soil formation?
What is a “soil profile”?
What are soil horizons? Types?
What effect(s) does climate have on soil formation? Examples?
What are the three main types of soil properties?
What is the significance of “categorizing” soils by these properties?
How are soils identified by texture?
How are soils identified by structure?
What other types of soil properties are there? Explain
How/where do soils fit into natural cycles/systems
in terms of interactions with atmosphere, hydrosphere, etc.?
in terms of e.g., the nitrogen cycle?
How are soils classified? Significance?
Distribution/examples of soil classification?
What are soil phases?
What are the “engineering properties” of soil? Significance?

4. What is the soil/erosion loss equation? How used? Significance?
What is sediment pollution?
How do human activities affect soils?
What are the main problems associated with soils?
How do the following affect soils?
- Urbanization
- Off-road vehicles
- Land use
- Soil pollution
What is desertification? What are the driving forces? Explain
What factors affect desertification?
Where do deserts occur? Where is desertification occurring? Significance?
What is the significance of swelling/shrinking of soils?
What is the significance of acid mine drainage on soil?
What are soil surveys? Explain
What are some types/examples of corrective measure used to address problems associated with soils?

5. The word "soil" means different things to different people
Farmers:
That part of the earth's surface contained decayed and organic material in sufficient quantity to grow plants and crops.
Geological:
Unconsolidated, unlithified residual (left over) material from underlying parent rock which supports root growth
Soil Science:
Altered solid earth material that can support rooted plant life
Engineering:
Solid earth material that can be moved without blasting

6. Roles of Soils in the Environment
Land use planning (suitability)
Soil erosion
Agriculture
Construction
Waste management (interactions between waste, soil, water)
Natural hazards: land use planning in terms of:
Floods
Landslides, slope stability
Earthquakes

7. Soil Formation Soil formation begins with weathering
Weathering: Physical and/or chemical breakdown of rocks (open system):
Physical (mechanical) Processes: Big ones to little ones
Abrasion
thermal (expansion/contraction)
frost wedging
Chemical Processes: Dissolution & alteration (congruent vs. incongruent dissolution w/residue)
Soil Formation depends on:
Climate
Topography
Parent material
Time/age of soil
Organic processes

8. Physical Weathering Making big pieces into smaller pieces
increases surface area available for chemical weathering

9. Chemical Weathering Alteration (e.g, feldspar to clay+quartz)
Dissolution

10. Chemical Weathering Reactions

11. Soil Profile Development
Variables:
Parent material
Climate
Topography
Time (Soil age / extent of development)
Organic activity

12. Soil Horizons

13. Climatic Effects on Soil Formation

14. Soil Properties/Indicators
Color
Dark: indicative of organic material (O, A horizons) or iron
Light:
Whitish: Indicative of leaching (E-horizon)
Extensive leaching of iron, Al
Presence of carbonates
Yellow, brown, red (B-horizon)
Be careful (e.g., basaltic material, volc. ash)
Texture (particle size)
Structure

15. Soil Texture (particle size)
Depends on relative proportions of sand-, silt, -clay sized particles

16. Soil Structure Aggregates of soil particles = peds
Peds classified by shape (structure)

17. Other Soil Features/Characteristics
Relative profile development
Weakly developed
Moderately developed
Well developed
Soil Chronosequences
Arrangement from youngest to oldest
Significance? When needed or used? (see fig.)
How determined (if not obvious)?

18. More Soil Features/Characteristics
Soil Fertility
Definition: Capacity of soils to supply nutrients (N, P, K)
Significance?
Water in Soils
Soil moisture
Saturated
Unsaturated

19. Cycles / Systems Associated With Soils

21. Soil Classification Soil Taxonomy Engineering Classification
(See Table)
Engineering Classification

23. Engineering Properties of Soils
Soil phases
Solid material
Liquid
Gas
Soil Properties
Placsticity
Soil strength
Cohesion
Friction
Sensitivity
Compressibility
Erodibility
Permeability
Corrosion
Ease of excavation
Shrink-swell potential

24. Soil Erosion/Loss
Loss of volume, mass, or weight of soil from a location in a specified time and area e.g., kg/yr/hectare
Universal Soil Loss Equation
A = RKLSCP
Significance (of factors & result)?
A = long-term avg. annual soil loss for the site
R = long-term rainfall runoff erosion
K = Soil erodibility index
L = Hillslope/length factor
S = Hillslope/gradient factor
C = Soil cover factor
P = Erosion-control practice factor

25. Sediment Pollution: Sediment (eroded soil) as a pollutant
How is soil pollution a negative resource?
Depletes useable soil
Reduces quality of water it enters
Deposition of sterile materials
Control/Reduction: Techniques, Examples (see text)
Figure

27. Land Use & Other Soil Problems
Human activities affect soils by influencing patterns, amounts, and intensity of:
Surface-water runoff
Erosion
Sedimentation
Conversion/manipulation of natural areas & surface water
(see Figures 3.12, 3.13)

29. Soil Erosion due to diversion of runoff water

31. Land Use & Other Soil Problems
Urbanization
Off-Road Vehicles
Soil Pollution
Desertification
Others

32. Effects of land use on sediment yield; with sharp peak during construction & urbanization

33. Off-road vehicle excavation
Urbanization erosion

34. Land Use & Other Soil Problems
Urbanization
Off-Road Vehicles
Soil Pollution
Desertification
Others

36. Land Use & Other Soil Problems
Urbanization
Off-Road Vehicles
Soil Pollution
Desertification
Driving Forces:
Overgrazing
Deforestation
Soil erosion
Poor irrigation drainage
Overdraft of water supplies
Off-road vehicle erosion

37. Desertification Factors:
Declining water table
Salinization of soil & near-surface water
Enhanced soil erosion (wind and/or water)
Damage to native vegetation

38. Extent of desertification of arid lands of the world

39. Land Use & Other Soil Problems
Urbanization
Off-Road Vehicles
Soil Pollution
Desertification
Others
Swelling & shrinking
Acid mine waters

40. Swelling & Shrinking of Soil Minerals

42. Soil Surveys & Land Use Planning
Descriptions
Soil Maps (types, extent, properties)
Information for identifying potential problems/issues BEFORE use (e.g., construction)

43. Corrective Measures Erosion Controls Pollution abatement Others?
Terracing, contour stripping
Vegetation barriers
Water/sediment basins/reservoirs
Characterization & planning
Pollution abatement
Treament, e.g., bioremediation
Others?

45. Storm water sediment basin

46. Summary/Overview Definitions of soil Variables (explain)
Roles of soils in environmental geology
Land use planning
Waste disposal
Evaluation of natural hazards
Formed from rock interactions in the hydrologic cycle (explain)
Variables (explain)
Climate
Topography
Parent material
Time
Organic activity
Soil processes form distinctive layers (horizons)
Soil Properties:
Color
Texture (particle size)
Structure (peds)

47. Learning Objectives Soils terminology & processes
Interaction of water in soil processes, soil fertility
Classification of soils (familiarity)
Engineering properties of soil
Relationships between land use and soils
Sediment pollution
Desertification