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Erosional Landforms

Fluvial Erosional Landforms are landforms created by the erosional activity of rivers.Various aspects of fluvial erosive action include:....

Fluvial Erosional Landforms are landforms created by the erosional activity of rivers.Various aspects of fluvial erosive action include:

  • Hydration:the force of running water wearing down rocks.
  • Corrosion:chemical action that leads to weathering.
  • Attrition:river load particles striking, colliding against each other and breaking down in the process.
  • Corrasion or abrasion:solid river load striking against rocks and wearing them down.
  • Downcutting (vertical erosion):the erosion of the base of a stream (downcutting leads to valley deepening).
  • Lateral erosion:the erosion of the walls of a stream (leads to valley widening).
  • Headward erosion:erosion at the origin of a stream channel, which causes the origin to move back away from the direction of the stream flow, and so causes the stream channel to lengthen.

A landform is a feature on the Earth’s surface that is part of the terrain . Mountains, hills, plateaus, and plains are the four major types of landforms. Minor landforms include buttes, canyons, valleys, and basins.

Tectonic plate movement under the Earth can create landforms by pushing up mountains and hills. Erosion by water and wind can wear down land and create landforms like valleys and canyons. Both processes happen over a long period of time, sometimes millions of years.

River Valley Formation
  • The extended depression on ground through which a stream flows throughout itscourse is called a river valley.
  • At different stages of the erosional cycle the valley acquires different profiles.
  • At a young stage, the valley is deep, narrow with steep wall-like sides and a convex slope.
  • The erosional action here is characterized by predominantly vertical downcutting.
  • The profile of valley here is typically ‘V’ shaped.
  • A deep and narrow ‘V’ shaped valley is also referred to as gorge and may result due to downcutting erosion.
  • As the cycle attains maturity, the lateral erosion becomes prominent and the valley floor flattens out. The valley profile now becomes typically ‘U’ shaped with a broad base and a concave slope.
  • Young rivers close to their source tend to be fast-flowing, high-energy environments with rapid headword erosion, despite the hardness of the rock over which they may flow.
  • Steep-sided “V-shaped’ valleys, waterfalls, and rapids are characteristic features.
  • Mature rivers are lower-energy systems. Erosion takes place on the outside of bends, creating looping meanders in the soft alluvium of the river plain. Deposition occurs on the inside of bends and on the river bed.
  • Old Age
  • At a river’s mouth sediment is deposited as the velocity of the river slows.
  • As the river becomes shallower more deposition occurs, forming islands and braiding the main channel into multiple, narrower channels.
  • As the sediment is laid down, the actual mouth of the river moves away from the source into the sea or lake, forming a delta.
  • A waterfall is simply the fall of an enormous volume of water from a great height.
  • They are mostly seen in youth stage of river.
  • Relative resistance of rocks, relative difference in topographic reliefs, fall in the sea level and related rejuvenation, earth movements etc. are responsible for the formation of waterfalls.
  • For example, Jog or Gersoppa falls on Sharavati (a tributary of Cauveri) has a fall of 260 metres.
Pot Holes
  • The kettle-like small depressions in the rocky beds of the river valleys are called pot holes which are usually cylindrical in shape.
  • Potholing or pothole-drilling is the mechanism through which the grinding tools (fragments of rocks, e.g. boulders and angular rock fragments) when caught in the water eddies or swirling water start dancing in a circular manner and grind and drill the rock beds of the valleys like a drilling machine.
  • They thus form small holes which are gradually enlarged by the repetition of the said mechanism.
  • The potholes go on increasing in both diameter and depth.
  • A meander is defined as a pronounced curve or loop in the course of a river channel.
  • The outer bend of the loop in a meander is characterized by intensive erosion .
  • The inner side of the loop is characterized by deposition, a gentle convex slope, and is called the slip-off side.
  • Morphologically, the meanders may be wavy, horse-shoe type or ox-bow/ bracelet type.
Natural Levees
  • These are narrow ridges of low height on both sides of a river, formed due to deposition action of the stream, appearing as natural embankments.These act as a natural protection against floods but a breach in a levee causes sudden floods in adjoining areas, as it happens in the case of the Hwang Ho river of China.
Peneplane (Or peneplain)
  • This refers to an undulating featureless plain punctuated with low-lying residual hills of resistant rocks.
  • It is considered to be an end product of an erosional cycle.

Read more : Earth – Latitudes & Longitudes

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