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Bullet River and Sea Erosion
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Erosional Features
River erosion is the gradual removal of rock material from the river banks and bed.
A river erodes in the following ways:
Corrasion (abrasion):
    River and Sea Erosion
  • The river uses its load to grind against the bed and sides
  • The action would dislodge the materials and carry them away
  • This process operates in 2 ways (verticle--> depth; lateral--> width)
  • Potholes are the product of corrosion
  • The loosened materials that are being carried away collide against the river sides and bed and against one another
  • Over time, they would become smaller and eventually reduced to fine particles called silt
Solution (corrosion):
  • The solvent action of water dissolves soluble materials and carry them away in solution
Hydraulic action:
  • The breaking down of rocks
  • Removing and dragging rocks from the bed and banks of the river by the force of the running water (like a water jet)
  • Usually there are lines of weakness like joints and cracks in the river
  • The work of hydraulic action forms plunge pools (small lakes)
  • Circular depressions on the river bed
  • Formed by corrosion (abrasion)
  • Most effective in flood conditions
  • Pebbles which are trapped in hollows on the river bed are swirled about in turbulent/ fast flowing water
Plunge pools:
  • A large depression at the foot of a waterfall
  • This depression is deepened by hydraulic action of the plunging water
  • Condition: likely to form when the water plunges into less resistant rocks
  • It may be further enlarged by rock debris swirling about by turbulent water at the base
    River and Sea Erosion
  • A series of very short and fast falls
  • Condition: an area of alternating bands of resistant and less resistant rocks
  • Vertical flows of fast moving water flowing from great heights
  • River and Sea Erosion
  • Formed by 2 ways: - Due to unequal resistance of rocks or faulting
    • Unequal resistance- less resistant rocks are eroded more rapidly than resistant rocks
    • As a result, there is a change in gradient
    • By faulting- displacement of rocks results in a difference in height between 2 rocks, water plunges downwards
    River and Sea Erosion
  • Valleys which are steep sided, deep and narrow
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