Weathering

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Weathering

• Depends upon
• Hardness of rock
• Harder rocks resist physical (mechanical
  weathering)
• Chemical stability of rock
• Chemically stable minerals resist chemical
  weathering
• Climate
• Cold climates favor physical weathering
• Warm most climates favor chemical weathering

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Distribution of Rock Types
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• More resistant rock on top

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Chemical weathering
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Weathering

• Chemical
• Rocks are broken down through chemical changes
• Common in warm, humid climates
• Example Limestone highly affected by acids

• Mechanical
• Rocks are broken down through physical changes
• Common in harsher climates
• Example water freezing in cracks expands and
  breaks rock apart

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Increasing surface area increases rate of
weathering
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Soil

• Forms due to actions of weathering rock and
  living organisms
• Composed of organic and inorganic materials
• Form in layers (horizons)

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Physical Characteristics of Soil

• Color
• Texture (sand, silt or clay)
• Structure
• Nutrient content
• Moisture content
• All depend upon the environment in which the soil
  forms

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Soil Horizons
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Layers of Soils (Horizons)

• O Horizon fresh or partly decomposed organic
  matter
• A Horizon minerals and organic matter present
  (topsoil)
• E Horizon similar to A, but more crumbly in
  texture, and changed by leaching and dissolving
  of layers above
• B Horizon leached nutrients, fine particles
  (clay) and salts accumulate (subsoil)
• C Horizon larger pieces of weathered rock broken
  off of parent material. Roots not do not
  penetrate.
• Parent material unweathered rock (bedrock)
  usually granite, sandstone or basalt