1. Weathering and Soils

2. Marble headstones in Southern Vermont Weathering and Soils Granite headstone in Southern Vermont

3. Weathering and Soils l Mechanical Weathering- the physical breakdown of rocks l Chemical Weathering- reaction of rocks with water, acids, oxygen, etc.

4. Mechanical Weathering

5. Tectonic Jointing Mechanical Weathering

6. Exfoliation

7. Exfoliation

8. Exfoliation

9. Chemical Weathering Solution: H 2 O + CO 2 = H 2 CO 3 ( H + + HCO 3 - ) H 2 CO 3 ( H + + HCO 3 - ) in air (acid rain) in air (acid rain) acid gas Limestone dissolves readily CaCO 3 + 2 H + (aq) = Ca +2 + CO 2 + H 2 O Ca +2 + CO 2 + H 2 O

10. Chemical Weathering Solution: Karst Topography

11. Chemical Weathering Solution: Karst Topography

12. Chemical Weathering Karst Sinkhole- Florida

13. Chemical Weathering Karst Sinkhole- Florida

14. Chemical Weathering Tower Karst - China

15. Chemical Weathering Oxidation: Fe 2 SiO 4 + ½ O 2 = Fe 2 O 3 + SiO 2

16. Chemical Weathering

17. Chemical Weathering Differential Weathering

18. Weathering can preferentially dissolve out mafics & increase the sialic component in sediments to yield “granite”

19. Chemical Weathering What happens when granite is weathered? The biotite and hornblende will undergo hydrolysis to form clay, and oxidation to form iron oxides. The feldspars will undergo hydrolysis to form kaolinite (clay) and release Na + and K + ions into solution The quartz (and muscovite, if present) will remain as residual minerals because they are very resistant to weathering.

20. Idealized soil profile from a humid climate at middle latitudes Zone of Leaching

21. Horizon Development and Climate

22. Soil textural classes

23. Topsoil ecosystem in a temperate climate

24. Effect of climate on soil development

25. Chemical Weathering Transported Soils

26. Wind-blown Glacial Loess Deposits

28. The Principal Soil Types

29. Effect of climate on soil types tundra soils Precipitation Temperature cold hot cool lowhigh50 cm/yr pedalferspedocals laterites tundra soils

30. Principal soil types in the USA

31. Effect of climate on soil types A typical pedocal with white caliche (CaCO 3 ) deposits in a shallow B horizon

32. Effect of climate on soils Making laterite bricks Temple at Angkor Wat Cambodia (700 yrs old) Laterite Tundra soil

33. A Newer Classification of Soil Types Pf Pc Pf Pf, Pc L Pf, L

34. Rates of soil formation: Central USA: ~ 1 cm/100 years in very porous and permeable rock Humid N. Carolina: ~ 1 cm/5 years“ Granite may require over 1000 years for a cm

36. Both Ends of the Erosion Problem Serious soil erosion and gully formation related to diversion of water runoff over a few months in central California Sediment pollution following heavy rains in North Carolina

37. Soil Degradation l Erosion l Deforestation l Agricultural depletion l Contamination - Pollution F Salinization F Pesticides F Chemical additions and spills l Urbanization l Desertification l Overgrazing

38. Raindrop impact: millions in a single shower hit at ~ 30 mph Soil Erosion

39. Rill-wash and gullying in loose and poorly-consolidated soils Soil Erosion

44. Number of dust storms during the month of March, 1936 Soil Erosion

45. Effects of logging in Madagasgar

46. Soil Erosion Figure 3.12:(a) a natural forested slope (b) the same slope following a clearcut

47. Soil Erosion Figure 3.12:(c) the same slope after conversion to farmland (b) the same slope following urbanization

48. Soil Erosion 1968 motorcycles first come to Deer Creek near Bakersfield, CA 1972 after only 4 years of ORV use little vegetation or topsoil remains

49. Soil Erosion ORV users increased from 21 to 38 million between 1982 and 1992 ATVs rip through a marsh in West Virginia Great Grizzly Hike, Montana

50. Soil Erosion 1985 photo of bulldozer and jeep tracks in Alaskan tundra made in 1946

51. Soil Erosion

52. Salt accumulation due to irrigation in an arid climate: San Fernando Valley

53. Worldwide Distribution of Salt-affected Soils

55. Chemical Contamination of Soils

56. Grain production levels off while population continues to grow

57. Strip-croppingand Contour plowing Combating Soil Degradation

58. Rice terraces in Asia Combating Soil Degradation

59. No-tillFarming