Soil Formation

1
Soil Formation Composition

• Mugg
• 6th Grade Science

2
Soil Formation

• Soil is the loose, weathered material on the
  Earths surface in which plants can grow.
• Soil forms as rock is broken down by weathering
  and it then mixes with other substances on the
  Earths surface.
• Soil is constantly being formed.
• Cool site on soil formation
• What on Earth is soil

3
Bedrock

• Wherever bedrock is exposed new soil is
  constantly being formed.
• Bedrock is the solid layer of rock beneath the
  soil.
• Once the bedrock is exposed the it begins to
  gradually weather away into smaller pieces.

4
Soil Composition

• Soil is more than just weathered bedrock.
• Soil is the mixture of rock particles, minerals,
  decayed organic material, air and water.
• Soil composition depends on the type of bedrock
  that is there and the clay.
• Humus a dark colored substance that forms as
  plants and animal remains decay.

5
Soil Texture

• Particles of soil are classified by there size
• Gravel
• Particles of sand
• Silt particles
• Clay particles, which are smaller than a period
  in a book.
• Click here for size comparisons
• Soil texture is important for plant growth.
• Soil that is made up of about equal parts clay
  sand and silt is called loam.

6
Soil Horizons

• Soil Horizon is a layer of soil that differs in
  color and texture from the layers above or below
  it.
• Horizon A- top soil
• Horizon B- subsoil consists of clay
• Horizon C- contains only partly weathered rock.

7
Life in Soil

• Some soil organisms mix the soil and make space
  in it for air and water. Other soil organisms
  make humus, the material that makes the soil
  fertile.
• As plants shed leaves they form a loose layer
  called litter.
• Decomposers are the organisms that break the
  remains of dead organisms into smaller pieces and
  digest them with chemicals.
• Take a look under ground