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2.4: Activity 3 - Weathering

  • Page ID
    14438
  • Part 1

    Your instructor has set up 2 beakers on a laboratory bench. Each beaker has a rock immersed in some type of liquid. Beaker #1 is filled with soda water, while beaker #2 contains a soil ped. Record the pH of the soda water, then submerge the ped into the soda water beaker. After the reaction has subsided, measure the pH of the solution. Record initial and final pH of the solution.

    Initial pH: _________

    Final pH: _________

    1. What are your predictions for what will happen when the liquids are added?
    2. List your observations:
    3. Explain the chemical process you observed:

    Part 2

    Your instructor has set out pictures detailing redoximorphic features displaying Oxidation and Reduction reactions. Observe each photo and detail your observations in the section below.

    1. Observe the picture on display for gleyed soils (Image 1). Describe the appearance of the gleyed soil.

    2. Observe the colors of the mottled soil on display (Image 2). Describe the appearance of the mottled soil.
    3. What are the physical (i.e. color) and chemical (i.e. form of Fe) properties of a gleyed/reduced soil?
    4. What environmental condition causes soils to become gleyed?
    5. In the field, what soil topographic or slope position (i.e. summit, backslope, or toeslope) would be most conducive to the formation of reducing conditions or gleyed soils? Why?
    6. Most soils do NOT have gleyed horizons. If a gleyed horizon exists, which soil horizon is most commonly gleyed/reduced in a soil (Assume this soil has an impermeable layer at 100 cm)?
    7. Explain why this horizon (from Q #6) would be most commonly reduced or gleyed.
    8. Soil may have a mottled condition associated with a fluctuating water table. What are the physical and chemical properties of a mottled soil? What happens when the water table rises and falls in the mottled soil zone?
    9. Well oxidized soils are associated with what soil drainage condition? (See page 1-11 in the Red Book)
      • In the field, what soil topographic or slope position (i.e. summit, backslope, or toeslope) would be most conducive to the formation of strongly oxidizing conditions in a soil? Why?
    10. For most soils, which is likely to have the most oxides, and most likely to have an oxidized horizon? Why?
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