Geological action of wind

Geological work of the wind, deflation, wind abrasion, desert pavement,
ventifacts, desert dunes and sand sheets, sand seas or ergs, loess, coastal dunes, sand hills and
sabkhas, loess and evolution of deserts: Wind action and desert landscape

1. WIND ACTION
WIND ACTION

2. CONTENT
•1. Introduction
•2.Geological Action of Wind
•2.1. Erosional Processes and associated landforms.
•2.2. Transportation Processes
•2.3.Depositional landforms

3. INTRODUCTION
•Wind is the flow of gases on a large scale.
•Wind is the moving air which is an active agent in erosion,
transportation and deposition.
•The geological action by wind is also known as AEOLIAN
PROCESSES
•Its activity is particularly intensive in the deserts and semi deserts.
•The activity of wind is effective in areas that lack plant cover and
have a considerable seasonal temperature variation

4. GEOLOGICAL ACTION OF WIND
Wind Erosion And Associated Landforms

5. Wind Erosion refers to the progressive removal of
particles by the blowing action of wind.
Wind erosion is caused by 3 major processes.
They are;
1.Deflation
2.Abrasion
3.Attrition

6. DEFLATION
•The removal of finer particles like sand, silt and
clay by the eddy action of wind.
•The regions which experience intense and
sustained erosion are called Deflation zones

8. Deflation basin may continue to deepen until it reaches the water table. Thus forms a
shallow pond known as OASIS.

11. •The loose particles that are blown away by the wind serve
as tools for wearing away the surface with which it comes in
contact.(It is the impact of wind carriyingparticle against
exposed bed rock)
•It depends up on the velocity of wind.
•The landforms created by abrasion involves;
1.Pedestal rock
2.Ventifacts
3.Zeugen
4.Yardang
ABRASION

12. 1. Pedestal Rock
Those rock formation with wide top
and narrow bottom , it indicate that
more abrasion near the surface and
than at top.
EROSIONAL LANDFORMS FORMED BY ABRASION

13. 2. Ventifacts
•The pebbles faceted by the abrasive effect of wind blown
sand.
•Ventifactscharacterisedby one smooth surface of rock
is called EINKANTER.
•Ventifactswith 2 smooth faces are called ZWEIKANTER.
•And with 3 smooth faces are called DREIKANTER

15. 3. Zeugen
•Tabular masses of more resistant
rock resting on under-cut pillars
of softer rock.
•They are elongated in the
direction of prevailing wind and
are also known as Mushrom-
table.

16. 4.Yardang
It is grooved or furrowed topographic form produced by wind abrasion.
The grooves are elongated in the direction of prevailing winds and are
separated by sharp ridges.

17. ATTRITION
•Attrition is the grinding action.
•While on transit wind blown particles often collide with
one another and such mutual collision brings grinding of
particles. Thus the grains are reduced to smaller
dimensions.
Millet-seed sands: These are rounded desert sand grains, resulted through
the process of attrition.

20. PROCESESS IN WIND TRANSPORTATION

21. WIND DEPOSITION
•Wind formed deposits are called Aeolian
deposits.
•The rock particles in the Aeolian deposits are
generally well rounded and are sorted
according to their size and weight.
•Wind deposits are mainly two types
1.Accumulations of sand , called “Sand dunes”
2.Deposits of silt, called“Loess”

23. 1. SAND DUNES
•A dune is a hill of sand built either by wind.
•Dunes occur in different shapes and sizes.
•Most dunes have a gentle slope towards the wind-ward
side and a steep face towards the lee-side.
•The valley or trough between the dune is called
SLACK.
•A Dune field is an area covered by extensive sand
dunes.

26. Types of sand
dunes

27. 1.Crescent dune
•Crescent shaped dunes with a steep slip face on
the inward or concave side.
•Commonly known as BARCHAN

28. 2. Transverse dune
•A relatively straight elongate dune oriented perpendicular to the
wind direction.
•They are formed in areas with strong winds where more sand is
available

29. cv
3.Longitudinal dunes

30. 4.Parabolic
dunes
•U shaped mounds of sand with convex noses trailed by elongated
arms.
•These are formed around blowouts where the erosion of
vegetated sand leads to a U shaped depression

32. 2.Sand Seas or Erg
An erg is a broad, flat area of desert covered with wind swept sand
with little or no vegetative cover.

33. 3. LOESS
•Is a deposit of wind blown silt and clay particles,
typically in the 20-25 micrometer size range
•these deposits are typically nonstratified and
have a grayish yellow colour.
•It composed of many minerals including quartz,
feldspar, hornblende and calcite.

34. 4. SABKHA
•Originated from an Arabic word meaning SALT FLAT.
•Sabkhas are forming along coastlines and are
characterized by evaporite-carbonate deposits with some
siliclastics.

37. 8. Ripple mark
Wave like undulations developed on the rock
surface by wind blown sands.

38. THANK YOU