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Weathering and Soils

Weathering and Soils. Granite headstone in Southern Vermont. Weathering and Soils. Marble headstones in Southern Vermont. Weathering and Soils. Mechanical Weathering- the physical breakdown of rocks Chemical Weathering- reaction of rocks with water, acids, oxygen, etc.

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Weathering and Soils

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  1. Weathering and Soils

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

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

  4. Mechanical Weathering

  5. Mechanical Weathering Tectonic Jointing

  6. Exfoliation Mechanical Weathering

  7. Exfoliation Mechanical Weathering

  8. Exfoliation Mechanical Weathering

  9. Limestone dissolves readily CaCO3 + 2 H+ (aq) = Ca+2 + CO2 + H2O gas Chemical Weathering Solution: H2O + CO2 = H2CO3 ( H+ + HCO3- ) in air (acid rain) acid

  10. Solution: Karst Topography Chemical Weathering

  11. Solution: Karst Topography Chemical Weathering

  12. Karst Sinkhole- Florida Chemical Weathering

  13. Karst Sinkhole- Florida Chemical Weathering

  14. Tower Karst - China Chemical Weathering

  15. Oxidation: Fe2SiO4 + ½ O2 = Fe2O3 + SiO2 Chemical Weathering

  16. Chemical Weathering

  17. Chemical Weathering Differential Weathering

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

  19. What happens when granite is weathered? • The biotiteand hornblende will undergohydrolysis to form • clay,andoxidation to form iron oxides. Chemical Weathering • The feldspars will undergo hydrolysis to form kaolinite (clay) and release Na+ and K+ ionsinto 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

  27. Wind-blown Glacial Loess Deposits

  28. The Principal Soil Types

  29. hot hot laterites Temperature pedocals pedalfers tundra soils cool cold low 50 cm/yr high Precipitation Effect of climate on soil types tundra soils

  30. Principal soil types in the USA

  31. Effect of climate on soil types A typical pedocal with white caliche (CaCO3) deposits in a shallow B horizon

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

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

  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

  35. 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

  36. Soil Degradation • Erosion • Deforestation • Agricultural depletion • Contamination - Pollution • Salinization • Pesticides • Chemical additions and spills • Urbanization • Desertification • Overgrazing

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

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

  39. Soil Erosion

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

  41. Effects of logging in Madagasgar

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

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

  44. 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

  45. 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

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

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