Saturday, 12 January 2013

Erosion, Transportation and Deposition

Types of Erosion:

Hydraulic action is the scouring of the bad and banks of a river by the sediment being transported in it. As the velocity of the river increases, turbulent flow lifts loose sediment.

Abrasion/ Corrasion is the wearing away of the shoreline by sediment carried in waves (sandpaper action).

Corrosion includes
            -Dissolving of carbonate rocks (like Limestone)
            -The evaporation of salt crystals which expand on formation and help the rocks to disintergrate

Attrition is the reduction and rounding of particles carried in the river by repeated collision with each other and the shore.

Factors effecting the Rate of Erosion:

1. Volume of water
2.Gradient of channel
3. Height of water above base level

Types of Transportation:

Saltation is when smaller materials (pebbles to sand) may be temporarily lifted fro the river bed and bounced along in a hopping motion.

Suspended load usually forms the bulk of sediments transported by rivers and comprises of fine muds and clays up to sand.

Dissolved/solution load is when weak acids (like carbonic acid) gradually act on more soluble rocks, gradually removing material from solution.

Traction is when large rocks like boulders are rolled along the river bed.

Deposition happens when:
-There's a decrease in Velocity/energy (decrease in the competence)
   -Decrease in depth of water
    -Decrease in discharge
     -Water enters lake or sea
      -Reduction in the gradient

Factors affecting River Velocity:

1.Roughness of river's bed and banks
2. Channel cross section/shape
3. Slope of channel

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