- Soil erosion refers to the detachment and relocation of the topsoil from the land, primarily caused by natural agents such as wind and water.
- This natural phenomenon can occur gradually over an extended period, known as geological erosion, or it can accelerate rapidly due to human activities like overgrazing and deforestation.
- The processes of weathering and erosion contribute to the simultaneous occurrences of ‘degradation’ and ‘aggradation.’
- Erosion, being a mobile process, involves the movement of soil materials, while weathering remains a static process where disintegrated materials undergo no motion except for falling under the influence of gravity.
WATER EROSION
- Running water stands as a prominent force in soil erosion, carrying away soil particles through various mechanisms.
- Soil erosion by water manifests through raindrops, waves, or ice, and its nature and intensity lead to different classifications such as raindrop erosion, sheet erosion, rill and gully erosion, stream bank erosion, landslides, coastal erosion, and glacial erosion.
Raindrop Erosion or Splash Erosion:
- Raindrops, approximately 5 mm in diameter and moving at a velocity of 32 km/hr, behave akin to tiny bombs when hitting exposed soil.
- The impact of raindrops displaces soil particles, disrupting soil structure.
- Presence of vegetation shields the soil from direct impact, preventing erosion in vegetated areas.
Sheet Erosion:
- Continuous rainfall causes displaced soil particles to fill spaces between soil particles, hindering water seepage into the soil.
- Surface runoff exacerbates erosion, leading to sheet or wash-off erosion.
- Weathering and erosion contribute to leveling irregularities in landforms, forming a peneplane.
Rill and Gully Erosion:
- In rill erosion, finger-like rills appear on cultivated land after undergoing sheet erosion, gradually increasing in width and depth each year.
- Gully erosion involves the removal of soil along drainage lines by surface water runoff.
- Gullies form as rills enlarge, and their movement continues through headward erosion or slumping side walls.
- Extensive gullies give rise to badland topography, such as the Chambal Ravines.
- Further erosion of gully beds results in the formation of ravines, with depths extending up to 30 meters or more.
- Ongoing erosion in ravines may lead to the creation of canyons, characterized by significant depth and width, as exemplified by the Grand Canyon on the Colorado River.
Streambank Erosion:
- The process of soil erosion from the banks or shores of streams or rivers, caused by the flowing water, is termed as streambank erosion.
- In areas where rivers alter their course, rapid erosion of river banks can occur.
- Streambank erosion poses a threat to nearby agricultural lands, highways, and bridges.
Landslide:
- A landslide refers to the abrupt mass movement of soil.
- It is triggered by the instability or loss of balance in a landmass concerning gravity.
- Excessive water or moisture in the earth mass contributes to the loss of balance.
- Gravity acts on the unstable landmass, causing large chunks of surface materials like soil and rocks to slide down rapidly.
Coastal Erosion:
- In coastal regions, waves striking the coast can inflict substantial damage to the soil.
- Cyclones during landfall lead to storm surges, resulting in the destruction of beaches and the removal of the top layer of soil.
- Estuaries experience damage to surrounding banks from tidal bores.
Glacial Erosion:
- In polar regions and high mountainous areas like the Himalayas, soil erosion is induced by slowly moving glaciers.
- This phenomenon is known as glacial erosion.
WIND EROSION
Wind Erosion in Arid and Semi-Arid Regions:
- Wind erosion, also known as aeolian erosion, is particularly prominent in arid and semi-arid areas.
- Deserts experience high-speed winds due to the absence of physical obstructions.
- These winds carry away the fertile, arable, and loose soils, leaving behind depressions devoid of topsoil.
- The formation of depressions in deserts marks the initial stage in the creation of oases. Oases form when underground water accumulates above rocks in these depressions.
Wind Erosion Processes:
- Fine and medium sands are transported by wind in a series of bounds and leaps, a phenomenon known as saltation.
- Small sand and dust particles are carried over considerable distances through the air in a process referred to as suspension.
- Coarse sand, while not usually airborne, is rolled along the soil surface, a type of erosion termed surface creep.
- Very coarse sand and gravels, being too large to be rolled by wind, result in surfaces covered with coarse fragments. This characteristic arid soil surface is identified as desert pavement.
FAQs: Soil Erosion – Wind Erosion, Water Erosion
1. What is soil erosion, and what are its primary causes?
A: Soil erosion refers to the detachment and relocation of topsoil from the land, primarily caused by natural agents such as wind and water. Causes include natural processes like geological erosion and human activities such as overgrazing and deforestation.
2. How does water erosion occur, and what are its different classifications?
A: Water erosion, driven by running water, occurs through raindrops, waves, or ice. Classifications include raindrop erosion, sheet erosion, rill and gully erosion, stream bank erosion, landslides, coastal erosion, and glacial erosion.
3. What is raindrop erosion, and how does vegetation impact it?
A: Raindrop erosion involves raindrops, acting like tiny bombs, hitting exposed soil. Vegetation shields soil from direct impact, preventing erosion in vegetated areas.
4. Explain sheet erosion and its connection with rainfall.
A: Sheet erosion occurs as displaced soil particles fill spaces between soil particles during continuous rainfall. It hinders water seepage into the soil, contributing to surface runoff and erosion.
5. What is the difference between rill and gully erosion, and how are badland topography and ravines formed?
A: Rill erosion involves finger-like rills on cultivated land, increasing in size each year. Gully erosion is the removal of soil along drainage lines. Gullies form from enlarged rills, leading to badland topography and the creation of ravines.
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