Aeolian processes and landforms
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This document summarizes aeolian (wind-related) processes and landforms. It describes the three main aeolian processes of erosion, transportation, and deposition by wind. Erosion occurs through deflation, corrasion/abrasion, and attrition. Transportation is by saltation, suspension, and rolling/traction. Deposition results from decreases in wind velocity. Aeolian landforms include erosional features like ventifacts, yardangs, and desert pavements, as well as depositional landforms such as loess, dunes, and ripples that are formed by the accumulation of wind-blown sediments. Different types of dunes like barchan, transverse, and parabolic d
Aeolian processes and landforms
- 1. seminar on AEOLIAN PROCESSES AND LANDFORMS Presented by, Monisha G Y 1st MSc Geology Under The Guidance of, Prof. K G Ashamanjari D.O.S In Earth Science
- 2. CONTENTS 1. INTRODUCTION 2. AEOLIAN PROCESSES EROSION TRANSPORTATION DEPOSITION 3.AEOLIAN LANDFORMS EROSIONAL LANDFORMS DEPOSITIONAL LANDFORMS 4.CONCLUSION 5.REFERENCE
- 3. WIND • Moving air mass is known as the WIND. • Produces varieties of landforms by erosion and deposition. • It cannot develop any landscapes by itself - requires some materials as tools(particles of sand, silt etc.).
- 4. EROSION TRANSPORTATION DEPOSITION METHODS FEATURES METHODS CAUSES NATURE OF DEPOSITS Deflation Corrasion or Abrasion Impact or Attrition Desert Pavement or lag deposits Cave rocks, Mushroom Table& Pedestal rock Yardang Ventifacts Saltation Suspension Rolling or Traction Loss of velocity, settling of heavy particles, rain Dunes Loess Ripples WIND EROSION TRANSPORTATION AND DEPOSITION
- 5. WIND EROSION Chiefly three methods: • Deflation: The lifting and removal of loose sand, dust particles from the Earth’s surface. Forms shallow basins called deflation basins. • Corrasion or Abrasion: The wearing down of solid rocks by the impact of wind borne particles. • Attrition: Wind blown particles collide each other and get worn.
- 6. TRANSPORTATION BY WIND Three methods: • Saltation: results from impact and elastic bounce. • Suspension: particles are lifted high into atmosphere and are carried great distances before they settle. • Rolling or Traction: the movement of particles on ground. The coarser fragments are carried in this way.
- 7. DEPOSITION BY WIND Causes: • Any obstruction to wind • Reduction in velocity • Increased load • Rain
- 8. AEOLIAN LANDFORMS • Are formed by the erosion and deposition of windblown sediments. • The sediments are generally sourced from deserts, glacial deposits, rivers, or coastal shorelines. • Aeolian sediments are often composed of well- rounded, sand-to silt-sized particles, that are weathered by wind abrasion during transport. • Sediments are deposited when the velocity of the wind falls and there is not enough energy available to entertain and transport the sediments. Sands will begin to accumulate wherever they are deposited and often continue to move along the ground.
- 9. EROSIONAL LANDFORMS 1. VENTIFACT • Formed by abrasion effect. • Stones with flat surfaces. • Commonly distinguished by two or more flat faces meeting at sharp ridges, generally well polished. • The windward face of the rock is flattened and smoothened. • If has one smooth surface then known as EINKANTER and if three DREIKANTERS.
- 10. Ventifact shaped by wind abrasion into flat surface
- 11. 2. YARDANG • A yardang is an elongate ridge or remnant rock feature sculpted by abrasive action. • Oriented parallel to the prevailing wind.
- 12. 3. MUSHROOM TABLE AND PEDESTAL ROCKS • Isolated rocks from which the base has been partially cut by the undercutting of the wind.
- 13. 4. DESERT PAVEMENTS OR LAG DEPOSITS • Formed when wind carries finer, more lightweight particles such as sand away. • Large particles are left behind and protected from further erosion – desert pavements. • Also called as desert armor. • The areas covered with large sized rocks are called Hamadas.
- 14. Desert Pavement
- 15. 5. DEFLATION BASINS • Depressions formed from barren unconsolidated material. • Formed by eddy air currents. • Also known as deflation hollows or blow outs. • Measure from few centimetres to several kilometres across. • Depth up to 10m.
- 16. Small deflation basins in sandstone formations in the Colorado Plateau
- 17. DEPOSITIONAL LANDFORMS 1. LOESS • Deposit of wind-blown dust derived either from deserts or glaciated regions. • Typically yellowish brown, composed mostly of silt-size grains of quartz, felspar and clay.
- 18. 2. SAND DUNES • Piles of sand deposited by wind • Leeward side (slipface) has a steeper slope. • Windward side is more gradual. LEEWARD WINDWARD
- 19. DIFFERENT TYPES OF DUNES A. Barchan • Crescent-shaped dune whose long axis is transverse to the dominant wind direction. • The wings or arms or horns are directed leeward side. • Concave in leeward and convex in windward side. • Formed from a unidirectional wind. • Single slipface.
- 21. B. Transverse Dunes • Long asymmetrical dunes that form perpendicular to wind direction. • Formed when the source of sand is elongated one and transverse to wind direction. • Single long slipface.
- 22. C. Parabolic Dunes • Crescent-shaped dunes whose long axis is transverse to dominant wind direction. • Convex in leeward side and concave in windward side. • Multiple slipfaces.
- 23. D. Longitudinal or Seif Dune • Sinuous dune that can be more than several kilometres long and height may go up to 100m. • Formed when direction of wind is constant. • More or less parallel to wind direction. • Crests may be sharp or rounded.
- 24. E. Star Dune • Large pyramidal or star shaped dunes with three or more sinuous radiating ridges from a central peak sand. • Has three or more slipfaces. • Does not grow along the ground but does grow vertically.
- 25. F. Dome • Mound of sand that is circular or elliptical in shape. • Has no slipfaces.
- 26. G. Reversing • Dunes that are intermediate between star and transverse dunes. • Ridge is asymmetrical and has two slipfaces.
- 27. 3. SAND RIPPLES • Miniature dunes within a dune (not more than 2 inches tall). • May form from cross winds and appear to be traveling in a different direction than the large dune.
- 28. CONCLUSION • Wind performs many geological work carrying loose silt and sand. • Deflation, abrasion and impact are chief mode of wind erosion. • Ventifacts, yardang, pedestal rocks, desert pavement are the important erosional features. • Wind transports particles by saltation, suspension and traction. • Depositional features include loess, dunes etc., • The barchans, transverse, longitudinal, parabolic, star etc are types of dunes. • They are developed and migrated according to the sand availability and wind directions.
- 29. REFERENCE • Anderson S. Robert., Anderson P. Suzanne (2010); Geomorphology The Mechanics and Chemistry of Landscapes;1st Edition; Cambridge University press, USA; 476-501 • Thomas S G. David (Editor)(1989); Arid Zone Geomorphology; 1st Edition; Belhaven Press, London; 209- 284 • Thornbury D. William; Principles of Geomorphology; 2nd Edition; New Age International Ltd, New Delhi; 288-301 • http://www.earthds.info/pdfs/EDS_16.PDF • http://www- esd.worldbank.org/esd/ard/groundwater/pdfreports/Pt8_A eolian%20Deposits.pdf