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.

20. Barchan
windward
leeward

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