Landforms Produced By The Wind, Transportation By Wind Part 3

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Landforms Produced by the Wind

Wind Action Moves The Mineral Particles When They Are In A Dry State And Unprotected By Vegetation Cover. These Conditions Are Found In Deserts And Semiarid Regions Of The World, Or On Sandy Shorelines.

Erosion By Wind: Loose Particles Laying On The Ground Surface May Be Lifted Into The Air Or Rolled Along The Ground By Wind Action. In The Process Of Wind Abrasion, Wind Drives The Sand And Dust Particles Against An Exposed Rock Or Soil Surface. When The Wind-Borne Materials Strike Against Each Other, They Are Reduced In Smaller Particles. This Process Is Called Attrition. The Removal Of Loose Particles From The Ground Is Termed Deflation.

Landforms Produced by Wind Erosion

Some Of The Topographical Features Made By Wind Erosion Are:

Mushroom Rocks Or Rock Pedestals: The Differential Erosion Results When Rocks, Consisting Of Alternate Hard And Soft Layers Are Subjected To Wind Abrasion. The Soft Layers Are Easily Eroded, But The Hard Layers Resist Erosion. Due To Undercutting Near The Base Or Due To Greater Amount Of Sand And Rock Particles Being Transported Close To The Ground, The Resulting Feature Resembles A Rock Pillar Shaped Like A Mushroom. It Is Called Rock Pedestal Or Mushroom Rock. They Are Common In The Sahara Desert, And Are Also Seen Near Jodhpur.

Mushroom Rock

Mushroom Rock

Mushroom Rock

Wind Eroded Basins: A Landform Produced By Deflation Is A Shallow Depression Termed A Blowout. The Qattara Depression In Egypt Is The Finest Example Of Such A Hollow.

Deflation Hollow

Deflation Hollow

Deflation Hollow

Transportation By Wind: Sometimes The Transported Material Is Deposited In Areas Very Far Away From The Place From Where The Dust Particles Have Been Picked. Winds Blowing From The Gobi Desert Carry Dust To The Northern Parts Of China. In Our Country Winds Blowing From The Thar Desert Bring Dust Particles To Western Uttar Pradesh And The Adjoining Parts Of Haryana And Punjab. This Transported Material Is Also Deposited In The Fertile Plains Of Uttar Pradesh.

Deposition By Wind: The Material Transported By Wind Starts Getting Deposited At A Particular Site Along Its Running Track Under Certain Conditions. The Conditions Favouring Deposition Are:

  • When The Amount Of Dust Particles Presents In The Air Exceed Its Carrying Capacity, A Part Of The Material Being Transported Is Deposited.

  • When The Speed Of The Wind Is Reduced, Its Carrying Capacity Is Also Reduced. The Material In Suspension Is Therefore Deposited.

  • When An Obstruction Comes In The Path Of The Wind, Air Has To Rise Above This Obstruction. When It Rises, The Velocity Of The Wind Is Reduced And It Starts Dropping Its Load. Thus, Material Is Deposited In The Form Of A Mound At The Foot Of The Obstruction.

Some of the Topographical Features Made by Wind Deposition Are:

Sand Dunes: Sand Dunes Are Of Different Types And Have A Variety Of Shapes. The Major Factors Affecting Their Formation Are:

  • Amount Of Sand Available

  • Direction And Force Of Wind

  • An Obstruction In The Path Of The Wind E.G. A Bush, A Stone Or A Dead Animal

As Long As The Wind Is Strong Enough To Carry The Sand, The Sand Dunes Are Mobile And They Keep On Shifting From One Place To Another. If Vegetation Or A Line Of Trees Starts Growing On The Dunes, They Become Fixed. They Become Stationary When They Are Blocked By A Hillock. In Case There Is No Such Obstruction, Sand Dunes May Bury The Agricultural Lands, Plains, And Settlements.

There Are Two Main Types Of Sand Dunes:

Barchan: One Common Type Of Sand Dune Is An Isolated Heap Of Free Sand Termed A Barchan Or Crescentic Dune. Barchan Has The Outline Of A Crescent, And The Points Of The Crescent Are Directed Downwind. On The Upwind Side Of The Crest, The Sand Slope Is Gentle And Smoothly Rounded. They Are Found In Large Numbers In The Sahara Desert.

Barchan Dunes

Barchan Dunes

Barchan Dunes

Seif Dunes: These Are Long, Narrow Ridges Of Sand That Lie Parallel To The Direction Of Prevailing Winds. The Winds Blow Straight Along The Corridors Between The Lines Of Dunes, Sweeping The Corridors Clear Of The Sand. However, Eddies Set Up In The Winds Blow Towards The Sides Of The Corridors, Depositing Sand There To Form These Narrow And Elongated Dunes. They Are Common In The Western Part Of The Thar Desert Of India.

Loess: In Several Large Areas Of The World, The Surface Is Covered By Deposits Of Wind Transported Silt That Has Settled Out From The Dust Storms Over Thousands Of Years. This Material Is Termed Loess. Loess Tends To Break Away Along Vertical Cliffs When It Is Exposed By The Cutting Of A Stream Or Grading Of A Roadway. The Thickest Deposits Of Loess Are Found In Northeast China, Where A Layer Over 30m Deep Is Common And A Maximum Thickness Of 100m Has Been Measured. Deposits Of Loess Also Occur In Mississippi Valley Of North America And North Of Central European Upland In Germany, Belgium, France, And Australia.