WEATHERING, SOIL, AND MASS WASTING

Soil

Soil is an interface where different parts of a system interact. Soil forms where the atmosphere, the hydrosphere, and the biosphere meet. It is the link between the inanimate world and living organisms.
The regoliths is the layer of rock and mineral fragments produced by weathering. The part of the regolith that supports vegetation is soil, a mixture of mineral, organic matter, water, and air.

Soil Texture

• based on properties of particle sizes
• influences the ability to retain and transmit air and water
• categories are based on percentage of clay, silt, and sand

Controls of Soil Formation

• Parent Material
  • weathering bedrock creates residual soils
  • unconsolidated sediment creates transported soils
    • usually soil development is faster because the parent material has already been weathered
• Time
  • the greater the time the less it will resemble the parent material
• Climate
  • temperature and precipitation are the most influential in soil formation
• Plants and Animals
  • influence the physical and chemical properties of a soil
• Slope
  • steep slopes have...
    • poorly developed soils
    • accelerated erosion causing soil to be thin or non-existent

Soil Profile

The vertical section through all soil zones or horizons is a soil profile.
There are five horizons in a well developed soil: O, A, E, B, C, and R. (surface to deep)
O and A horizons are the topsoil.
Leaching occurs when water dissolves the soluble materials in the upper soil and carries them to deeper soil zones.

Soil Types

There are hundreds of soil types throughout the world. We will study three basic soil types.

• Pedalfer
  • high in iron oxides and aluminum-rich clay
  • found in forest vegetation
• Pedocal
  • have more calcium carbonate
  • found in grasslands and brush vegetation
  • arid and semi-arid locations
• Laterite
  • form in hot, wet tropical climates
  • poor agricultural soils

Weathering can create ore deposits by concentrating minor amounts of metals into valuable deposits called secondary enrichment.