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Weathering: breaking rocks down

Weathering: breaking rocks down. Example of an external (surface) process (vs. internal process) Weathering occurs because many minerals in rocks are not stable at temperatures and pressures that exist on earth’s surface. Weathering: breaking rocks down.

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Weathering: breaking rocks down

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  1. Weathering: breaking rocks down Example of an external (surface) process (vs. internal process) Weathering occurs because many minerals in rocks are not stable at temperatures and pressures that exist on earth’s surface.

  2. Weathering: breaking rocks down Mechanical weathering: physical disintegration of rock (into smaller pieces). Chemical Weathering: chemical destruction of primary minerals, creation of secondary minerals (residuals) and dissolved ions. Air and water react with minerals.

  3. Mechanical Weathering

  4. Mechanical Weathering

  5. Mechanical Weathering

  6. What does this have to say about susceptibility of minerals to weathering?

  7. Chemical Weathering KAlSi3O8 + H+ + HCO3- + H2O ►► Al2Si2O5(OH)4 + K+ + HCO3- + SiO2

  8. Chemical Weathering KAlSi3O8 + H+ + HCO3- + H2O ►► Reactants Al2Si2O5(OH)4 + K+ + HCO3- + SiO2 Products

  9. Chemical Weathering KAlSi3O8 + H+ + HCO3- + H2O ►► Potassium feldspar Al2Si2O5(OH)4 + K+ + HCO3- + SiO2 Introduced in solution Clay mineral residual Carried away in solution

  10. Solution CO2 + H20 ◄► H2CO3 (formation of carbonic acid) Source(s) of CO2? in atmosphere in soil air from organic decomposition Weathering Chemical Weathering Processes:

  11. solid solution solution solution Weathering Chemical Weathering Processes: • Solution of calcite • CO2 + H20 ► H2CO3 • CaCO3 + H2CO3► Ca 2+ + 2 (HCO3)-

  12. Chemical Weathering Solution Big Spring ,Missouri

  13. Chemical Weathering Solution

  14. Oxidation-reduction Often earliest form of chemical weathering. affects ferrous silicates—such as? pyroxene, olivine, amphibole, biotite affects ferrous carbonates and sulfides. Example: Fe2SiO4 + 4 H2O + O2► 2 Fe2O3 + H4SiO4 Weathering Chemical Weathering Processes: FeS2 + O2 + H2O = Fe2+ H2SO4 (AMD)

  15. Diversion ditch Sediment pond BLGP Sludge pond Trend of upper seepage front Treatment ponds 100m

  16. Chemical Weathering Oxidation—Acid Mine Drainage (AMD)

  17. Chemical Weathering Oxidation—Acid Mine Drainage (AMD)

  18. Chemical Weathering Oxidation— Acid Mine Drainage (AMD)

  19. Weathering of Landscapes Fig. 5.12

  20. Weathering and Ores

  21. 1. Over time a granite mountain is reduced to boulder-sized pieces of granite. This is an example of ________________. a. mechanical weathering b. chemical weathering c. hydrolysis d. solution 2. In the chemical reaction shown below, a. where would this reaction occur? b. what are the reactants? c. what are the products? d. which reactants and products are minerals? Ions? e. which of the products is a residual? Which are in solution? KAlSi3O8 + H+ + HCO3- + H20 ►►► Al2Si2O5(OH)4 + K+ + HCO3- + SiO2

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