HTML University

Science Dept.

Geology and Soils GEO 100 Notes
Soil Genesis 1

1. THE IMPORTANCE OF SOILS "We cannot grow without it"

2. Definitions
   1. Soil is a collection of natural bodies on the earth's surface containing living matter and supporting or capable of supporting plants

   2. Upper Limit: Air or Water

   3. Lower Limit: Common Rooting Depth of the Native Perennial Plants (usage will usallly dictate the lower boundary)

3. Terminology
   1. Soil Horizons in Zoned Soils
      1. O - Layer of Organic Materials
         1. O₁ - Organic Remains Undecomposed (Recognized - Old A_oo)
         2. O₂ - Organic Remains Decomposed (Unrecognized - Old A_o)

      2. A Horizon - "Zone of Loss" Because of Clays and Nutrient Removal by Leaching
         1. A₁ Layer - Organic Rich A Layer Sometimes Called A_p for Plowed Layer
         2. A₂ Layer - Light-Colored Bleached Part of A Horizon = "Zone of Maximum Loss"
         3. A₃ Layer

      3. B Horizon - "Zone of Accumulation"
         1. B₁ Layer
         2. B₂ Layer - "Zone of Maximum Accumulation"
         3. B₃ Layer

      4. C Horizon - "Zone of (Broken) Parent Material"
         1. C₁ Layer
         2. C₂ Layer
         3. C₃ Layer

      5. R Horizon - Bedrock

4. Soil Terms
   1. The Soil Body - "The Pedon" - the Smallest Body that Represents a Soil

   2. The Soil Series: Several Soils that Form a Group

5. Factors Responsible for Soil Formation
   1. Parent Materials

   2. Climate

   3. Topography

   4. Biologic Factors Including Man

   5. Time