1. Earth Science Unit 1.4: Weathering and Soils

2. The Rock Cycle

3. Weathering The breakdown of rock near the surface due to surface processes, such as: Chemical Alteration –Solution & leaching of water –Biological action –Hydration Mechanical –Impact –Wedging: Frost, Plant Roots, Salt Crystal Growth, Expansion of Hydrated Minerals

4. Weathering Rates

5. Differential Weathering and Erosion

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

8. Surface Area and Weathering

9. Spheroidal Weathering

10. Spheroidal Weathering and Exfoliation

11. Spheroidal Weathering

12. Joints and Spheroidal Weathering

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

14. 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

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

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

17. 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

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

19. "The 7th Approximation" Degree of Weathering and B Horizon Development LittleSlightModerateLargeExtreme EntisolsAridisols InceptisolsAlfisols SpodosolsUltisols MollisolsOxisols Soils Defined by Special Constituent Materials AndisolsVolcanic Ash HistosolsPeat, Organic Matter Vertisols“Self-Mixing” Clay Soils GelisolsSoils on Permafrost

20. Soils of the U.S.

21. Typical Soil Profile (Spodosol)

22. Aridisol, Kuwait

23. Ultisols: Alabama Tennessee

24. Oxisol, California (a Paleosol)

25. Paleosol, Scotland