Soil

1
Soil

• 14.3

2
Regolith and Bedrock

• Regolith is the layer of weathered rock fragments
  that covers most of earths surface
• Bedrock is the solid unweathered rock that lies
  beneath the regolith

3
Characteristics of Soil

• Parent rock the weathered material that the
  soil originates from
• Residual Soils form directly above the parent
  rock, basically soils that form in place
• Transported Soils form from sediment carried by
  wind, water, or glaciers may look different from
  the bedrock that it sits atop

4
Soil Composition

• For the most part, soil is composed of weathered
  (decomposed rock). When weathering takes place a
  rock can decompose all the way to sand, silt, or
  clay.
• When plants and animals die, they decompose and
  turn into humus, which is dark, organic material
  that enriches soil.

5
Soil Composition

• Clay forms form parent rock rich in feldspar or
  minerals that contain aluminum
• Sandy soils- forms from parent rock like granite
  rich in quartz
• Black soils- rich in organic material dead
  stuff, poo
• Red soils made from iron-rich parent rocks

6
Soil Texture

• Clay- particles less than 0.004mm
• Silt- particles between 0.004 and 0.06mm
• Sand- particles between 0.06 and 2mm

7
Soil Profile

• A cross section of soils typically yeilds a soil
  profile. You can typically see layers in the
  soil, which are called horizons.
• Fully developed soils consist of three principle
  horizons A (topsoil- mixture of organic and
  small rock material), B (subsoil minerals from
  topsoil, clay, and humus), and C (partially
  weathered bedrock).

8
Soil and Climates

• The type of soil you have is dependant upon the
  type of climate you have
• Tropical Climate good, rich soil
• Desert Climate not a very good soil
• Artic Climate not very good

9
Topographic Effects on Soil

• The steeper the topography, the poorer the soil
  the good stuff gets washed or blown away
• The flatter the topography, most likely the soil
  is more rich because you can deposit nutrients in
  flat places