Geography Notes

Denudational Processes

Denudation is the process of lowering or sculpturing the earth surface by the activities of certain agents called denudation.  The word denude is an original Greek word for reduction, that is, lowering or cutting.  Therefore, denudation process are processes that contribute to lowering or reshaping the earth.

Types of Denudational Processes

Denudation involves four major processes and a fifth, which strictly speaking is not considered as properly belonging to this group.  They include;

  1. Weathering
  2. Erosion
  3. Transportation
  4. Mass Movement
  5. Deposition
  1. Weathering

Weathering has been defined as the decay or decomposition of rock materials in situ. The process of weathering may be physical, chemical or biological.

  1. Erosion

Erosion is the removal of weathered materials.  It involves the detachment of debris or classic materials (broken material). 

  1. Transportation

This involves the conveyance of the eroded materials away from the original point’s erosion by transporting agents such as running water, wind, ice, waves and gravity.

  1. Deposition

Deposition in its strict sense is not a Denudational process.  Rather, it belongs to a process of a gradation instead of degradation.

Major concepts of Weathering

The following major concepts are briefly explained below:

  1. In situ
  2. Disintegration
  3. Expansion and contraction
  4. Oxidation, carbonation, solution, hydrolysis
  5. Debri
  6. Definition of weather materials based on sources.

In situ: This means on the spot disintegration of materials.  This implies that no movement of any kind is involved.

Disintegration: is the detachment of the materials from the parent body.  It means splitting away of the debris or clastic materials.

Expansion and contraction

This is a physical weathering process which is caused by the action of heating during the day and cooling at night.  Daytime heating will produce expansion while night time cooling will imitate contraction.  This phenomenon of expansion and contraction is most common in hot desert landscapes where excessive heating during the day would cause expansion while night time radiation will result extreme cooling and contraction of rock surfaces.

Oxidation: This relates to the effects of atmosphere oxygen on rocks that contain iron materials, the oxidation process acts to reduce the iron material from its ferrous (Fe2) to its ferric ionized state (Fe3).  Oxidation or ionization results in the production of reddish surface on materials undergoing the process.  Oxidation is commonly screen in the rusting of metals particularly iron.

Carbonation: Solution and hydrolysis are different process of chemical reaction, which is facilitated by, water action. They shall be treated in detail below.

Debris: These are weathered materials which come in different shapes.  They may be called regolith, or elastic materials.

Definition of weather materials by source

  1. Aeolian deposits – wind derived materials.
  2. Marine deposits – from sources in the ocean
  3. Lacustrine materials – from lake source
  4. Fluvial materials –from source in rivers
  5. Fluvial glacial – derived from valley glaciers
  6. Glacial deposits – from sources of glaciations
  7. Volcanic deposits – from volcanic sources.

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