1. Weathering and Soils

3. The Rock Cycle

4. The Rock Cycle

5. Weathering Breakdown of Rock near the Surface Due to Surface Processes
Chemical Alteration
Solution & Leaching
Biological Action
Hydration
Mechanical
Impact
Wedging: Frost, Plant Roots, Salt Crystal Growth, Expansion of Hydrated Minerals

6. Never Safe From Weathering

7. Weathering Rates

8. Differential Weathering and Erosion

9. Differential Weathering and Erosion

10. Mass-Wasting Movement of Large Amounts of Material Downhill under Gravity
Creep
Mudflows
Slump
Rockfalls
Avalanches

11. Surface Area and Weathering

12. Surface-Volume Effects

13. Spheroidal Weathering

14. Spheroidal Weathering and Exfoliation

15. Spheroidal Weathering

16. Joints and Spheroidal Weathering

17. What Determines Soil Type
Climate
Vegetation
Drainage
Time
Parent Material
Residual - Transported
Least Important Factor for Mature Soils

18. Soil Formation Young Soils Strongest Influence Is Parent Material
Mature Soils
Strongest Influences: Climate, Vegetation, Drainage

19. Soil Formation Processes
Leaching from Surface
K, Mg, Na Ca Si
Al, Fe
Accumulation beneath Surface
Al, Fe in Humid Climates
Ca in Arid Climates

20. Soil Horizons and Profiles
Layers in Soil
Not Deposited, but Zones of Chemical Action
Soil Profile
Suite of Layers at a Given Locality

21. Principal Soil Horizons
O - Organic (Humus) Often Absent
A – Leaching
K, Mg, Na, Clay Removed
E - Bleached Zone - Present Only in Certain Soils
B – Accumulation
Absent in Young Soils
Distinct in Old Soils
Al, Fe, Clay (Moist)
Si, Ca (Arid)
C - Parent Material

22. Limits of Soil Formation
Balance Between:
Downward Lowering of Surface
Downward Migration of Horizons
If erosion rapid or soil evolution slow, soils may never mature beyond a certain point.
Extremely ancient soils may have lost everything movable

23. Soil Classification
This may be the most difficult classification problem in science because of the many factors involved.
Varied Bases for Classification
Parent Material
Special Constituent Materials
Maturity
Structure
Climate & Vegetation
Multiple Objectives
Scientific
Genesis & Evolution
Agricultural
Fertility
Most Effective Use
Engineering
Slope Stability
Expansion and Shrinkage
Stability of Excavations

24. "The 7th Approximation"
U.S. Soil Conservation Service
12 Soil Orders

25. Degree of Weathering and B Horizon Development Little Slight Moderate
"The 7th Approximation"
Degree of Weathering and B Horizon Development
Little
Slight
Moderate
Large
Extreme
Entisols
Aridisols
Inceptisols
Alfisols
Spodosols
Ultisols
Mollisols
Oxisols
Soils Defined by Special Constituent Materials
Andisols
Volcanic Ash
Histosols
Peat, Organic Matter
Vertisols
“Self-Mixing” Clay Soils
Gelisols
Soils on Permafrost

26. Soils of the U.S.

27. Typical Soil Profile (Spodosol)

28. Aridisol, Kuwait

29. Ultisols: Alabama Tennessee

30. Oxisol, California (a Paleosol)

31. Paleosol, Scotland