23. Indian-World Geography [Geomorphology] [Erosion and Drainage] [Part-23] [08-11-2024]

Contents :
-Erosion :
1. Soil Erosion : loosening and displacement of topsoil from the land due to the action of agents like wind and water.
-Nature of Soil Erosion : Slow (Natural Geological Erosion) or Fast (Erosion companied by Anthropogenic Activities-Deforestation and Overgrazing)
Note : Erosion is a mobile process [loosening of top soil + movement] whereas Weathering is a static process [loosening of top soil]
2. Water Erosion : Soil Erosion [Due to Water-External Agent] :
-Raindrop Erosion (Splash Erosion)
-Sheet Erosion (Wash Off Erosion) : Left over denuded land is called Peneplane
-Rill and Gully Erosion : Deepening of erosion in peneplane results in rill like projections and further results into Gully Erosion
Note :
Sequence of Soil Erosion :
-Undisturbed Soil Particles
-Disturbed Soil Particles : Weathering
-Disturbed Soil Particles + Movement : Erosion
-Sheet Erosion (Wash Off Erosion) : Erosion of soil particles in sheets
-Rill Erosion : Finger like projections formed after sheet erosion and deepening of the gullies
-Gully Erosion : Deepening of gullies due to intense erosion in the gullies
-Rill Erosion + Gully Erosion = Badland Topography
-Badland Topography + Headward Erosion = Ravine Beds
-Ravine Beds + Erosion = Canyons [Eg-Grand Canyon on the Colorado River]
3. Stream Bank Erosion
4. Landslides
5. Coastal Erosion
6. Glacial Erosion
7. Wind or Aeolian Erosion :
-Suspension : Small sand particles transported to long distances by air
-Saltation : Medium sand particles transported by leaps and bounds
-Surface Creep : Heavy sand particles transported by rolling along surface
-Desert Pavement : Very Heavy sand particles and gravels left make the surface coarse and forms a desert pavement
8. Fluvial Erosion
Drainage : Patterns formed by the streams, rivers, and lakes in a particular drainage basin.
Types of Drainage Patterns :
1. Concordant Drainage : Consequent, Subsequent, Obsequent and Resequent.
-Consequent : Rivers which follow the general direction of the slope
-Subsequent : Tributary stream that is formed by headward erosion along an underlying rock
-Obsequent : May form at right angles to the subsequent rivers and flow opposite to the direction of flow of the original consequent river
-Resequent : Flows in the same direction as that of the initial consequent drainage
2. Discordant or Insequent Drainage
-Antecedent Drainage or Inconsequent Drainage : River slope and the surrounding area gets uplifted, and the river sticks to its original slope, cutting through the uplifted portion like a saw (vertical erosion) and forming deep gorges
-Superimposed or Epigenetic (Discordant) or Superinduced Drainage : River flowing over a softer rock stratum reaches the harder basal rocks but continues to follow the initial slope, it seems to have no relation with the harder rock bed.
3. Others Drainage Patterns :
-Dendritic or Pinnate : Shape-Irregular tree branch
-Trellis : Short subsequent streams meet main (head) stream at right angles
-Angular : Tributaries join at right angles
-Rectangular : Main stream bends at right angles and the tributaries join at right angles creating rectangular patterns
-Radial : Tributaries from a summit follow the slope downwards and drain down in all directions
-Annular : Radial streams develop subsequent tributaries which try to follow circular drainage around the summit
-Parallel : Tributaries seem to be running parallel to each other
-Centripetal : In a low-lying basin, the streams converge from all sides
-Deranged : Uncoordinated pattern of drainage vacated by an ice-sheet
-Barbed : This pattern is the result of the capture of the main river which completely reverses its direction of flow, while the tributaries continue to point in the direction of former flow
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