HTML University

Science Dept.

Geology and Soils GEO 100 Notes
Soil Genesis II

1. Factors Responsible for Soil Formation
   1. Parent Materials

   2. Climate

   3. Topography

   4. Biologic Factors Including Man

   5. Time

2. Parent Materials
   1. General Categories
      1. Bedrock

      2. Glacial Deposits

      3. Loess

      4. Alluvial Deposits

      5. Marine Deposits

      6. Organic Deposits

   2. Minerals in Bedrock
      1. Feldspars
         1. Orthoclase (K) Can Weather to Clay
         2. Plagioclase (Na-Ca) Can Weather to Clay

      2. Pyroxenes (Ca, Mg, Na, Fe): Augite

      3. Amphiboles (Ca, Mg, Na, Fe): Hornblende

      4. Micas: Can Weather to Clay
         1. Muscovite
         2. Biotite (K)

      5. Quartz: Silica

      6. Iron Oxides: Red & Yellow Colors in Southeastern Soils
         1. Hematite
         2. Limonite
         3. Goethite
         4. Magnetite

      7. Carbonates:
         1. Calcite (Ca)
         2. Dolomite (Ca-Mg)

      8. Clays: Give Rise to Most of the Chemical and Physical Properties of Soils
         1. Kaolinite
         2. Montmorillonite
         3. Vermiculite
         4. Illite

      9. Other
         1. Apatite,(P)
         2. Gibbsite (A)
         3. Tourmaline (B)
         4. Zircon
         5. Pyrite (Fe-S)
         6. Gypsum (Ca-S)

   3. Rocks - The Rock Cycle
      1. Igneous

      2. Sedimentary

      3. Metamorphic

   4. Weathering
      1. Physical

      2. Chemical
         1. Oxidation

         2. Hydration

         3. Carbonation

      3. Biological

   5. Glacial Deposits eg. the Wisconsin Stage of the Pleistocene Lelt Behind Glacial Drift
      1. Till = Ground Moraine
      2. Outwash Materials

   6. Loess Deposits
      1. Windblown Silts + Productive Aglands
      2. Ka, Nb, Io, Il, Ind, W. Ky, Tenn, Miss

   7. Alluvial and Marine Deposits
      1. Alluvial
         1. Fans
         2. Floodplains
         3. Deltas

      2. Marine Coastal Plains
         1. Atlantic
         2. Gulf

   8. Organic Deposits
      1. Peat
         1. Fibrous
         2. Woody

      2. Muck - Organic Source of Vegetation Can not Be Identified

      3. Histosols
         1. Greater Than 16 in Thick
         2. 30% Organic Matter

3. Climate
   1. Type of Weathering

   2. Rate of Weathering

   3. More Moisture = More Leaching, Good for Vegetation

   4. Higher Temperature = Speed Up Chemical Weathering

4. Topography
   1. Affects Soil Drainage and Erosion

   2. Lowlands and Depressions
      1. Poor Soil Drainage
      2. Less Oxidized Caused By Water Logging
      3. Dark B Horizon, High in Organic Matter

   3. Uplands Good Drainage
      1. Well Aerated, Oxidized Soils
      2. Bright B Horizon
      3. Low Organic Content

   4. Steep Slopes
      1. Thin Soils
      2. Thin A and C (no B) Horizons

5. Vegetation
   1. Forest
      1. Thick O Horizon
      2. Thin Organic A₁
      3. Thick A₂ Horizon
      4. Little Organic Staining in B Horizon
      5. Trees Recycle Nutrients From Greater Depth But Not As Quickly As Grasses

   2. Grass
      1. Thick Dark Organic Rich A Horizon
      2. Organic Stains and Coatings Into the Upper B Horizon Due to Many Roots (50% of grass is root)
      3. Fast Recycling of Nutrients, Not As Deep As Forest Roots

6. Time
   1. Younger Soils
      1. Little Weathering
      2. Have Thin Profiles
      3. Thin A and B Horizons
      4. Usually Little Leaching

   2. Older Soils
      1. Highly Weathered
      2. Have Deeper Profiles
      3. Thick A₂ and B Horizons
      4. Usually Lost Their Plant Nutrients Through Leaching