What is Soil?
A natural body covering the earth’s surface in which plants are grown. Formed naturally by the effects of climate, living organisms, parent material, topography and time.
What are the functions of Soil?
- Medium for plant growth
- Stores and Filters water
- Habitat for soil organisms who recycle organic waste
- Engineering medium for construction
Soil forming factors include :
- Time
- Organisms
- Topography
- Climate
- Parent Material
- Man
What is Parent Material?
The original (mineral or organi) material from which the soil has developed.
Granite, Limestone, Shale etc.
- classified primarily by how they were deposited.
what are Igneous rocks?
Igneous rocks form when molten rock cools.
What are Sedimentary rocks?
rocks that form when sediment laid down by water is “cemented together” over time.
What are Metamorphic rocks?
Rocks that result from the transformation of existing rock when subjected to heat and pressure causing profound physical and/or chemical change.
- ex. Marble is formed by Metamorphised Limestone.
Parent Material
Name the two groupings:
Sedentary or Transported
Sedentary parent material is called:
Residuum
What is Residuum?
Sedentary Parent Material that develops when underlying rock weathers in place.
- Long and intense weathering
- Wide Distribution
Define Colluvium:
Transported Parent Material that detaches and moves down slop via gravity. Material is coarse and stony.
Define Alluvium and names the types:
Transported Parent Material via Rivers or Streams.
There are 3 types: floodplains, alluvial fans, deltas
Define Glacial Soil:
Transported Parent Material that consists of igneous, sedimentary, and metamorphic rock put in its place by glacial fomation and melting.
Define Aeolian Soil:
Transported Parent Material formed in silt sized particles deposited by wind.
Also called Loess. (pronunced “Luss”)
Define Marine soil :
Transported Parent Material that is formed in residue of ancient sea beds,
(Now Dry Land)
Define Lacustrine Soils:
Transported Parent Material formed in residues of ancient lakes.
Define CLIMATE as a soil forming factor:
- It determines the weathering of Parent Material.
- Temperature and Precipitation influence the rates of the Chemical and Physical process.
- Influences the breakdown of natural vegetation
What are the 3 Weathering factors in relation to the climate’s effect on Soil Formation?
- Physical / Mechanical weathering
- Chemical weathering
- Biological weathering
Define how the climate provides Physical /Mechanical weathering and Give examples:
Disintegration
- Change in temperature
- Action of H2O
- fragment transport
- freezing
- alternating wet/dry
- glaciers
- Action of wind
- Atmospheric electrical phoenomena ( Lightning)
Define how the climate provides Chemical weathering and give examples:
Decomposition
- Hydration (in contact with H2O)
- Hydrolosis
(the chemical reaction of anything with H2O)
- Dissolution (Dissolution usually occurs as minerals are dissolved through time. ex. headstones)
- Carbonation
- (Carbon dioxide when dissolved in water it forms carbonic acid) *
- Oxidation (rusting) /Reduction (The process of removal of oxygen)
Define Biological weathering and give examples:
** Disintegration + Decomposition**
- Man & Animals
- Higher plants & their roots
- Microorganisms
*
For a piece of material to be considered “Soil” it must be no bigger than:
2mm in size
Soils are comprised of:
- 45-50% Mineral Solids
- 0-5% Organic Solids
- 45 - 50% Liquids (H20) and Gases (ex. O2, CO2)
Lithification
The processes by which loose sediment is hardened to rock
