Aeolian process and landform by shivam soni B.Sc student of Department of Applied Geology Dr. Harisingh Gour University, Sagar Universityfinal ppt 2007

INTRODUCTION
 Wind processes are typically referred to as eolian
processes, which produce eolian land forms.
 The term eolian is derived from AEOLUS , the
Greek god of wind .
 It is important to understand the role that wind play
with respect to land form evolution because more
than one third of the land on our planet is
characterized as arid or semi arid .

AIM & OBJECT
 Our aim is to focus on arid Geomorphology & the way that
the flowing air, moves sadiment and shaps the landscape
 It provide us a good understanding of desert environments
& why they occure where they do.
 Desert & other dry lands are excellent places to study
geomorphology because the vegetation cover is relatively
thin & thus features such as rock structure & landforms are
easy to see.

ARID & SEMI-ARID REGIONS IN THE
WORLD
ARID & SEMI-ARID DESERT COVER 1/3 OF THE EARTH’S LAND SURFACE.

WIND ACTION CAN BE DIVIDED INTO THREE
PARTS:-
WIND ACTION
EROSION TRANSPORTATION DEPOSITION

WHY IN HUMID
REGION EXCEPT
ALONG SEASHORE
WIND EROSION IS
LIMITED?

Due to the prevalent cover of
grass & trees .
Also by the binding action of
moisture in the soil.

TYPES OF EROSION
EROSION
DEFLACTION ABRASION ATTRITION

DEFLACTION
DEFLACTIONDEFLACTION
 The process of lowering the land surface is called
“Deflaction”.
 Removal of sediments from a surface by wind action.
 In latin verb “deflatus” meaning ‘to blow away’.

DEFLACTION CAUSES
Desert pavement
Deflation hollow

DESERT PAVEMENT
 A resistant ,pavement- like suface created when
fine particles blow away & coarse sediments such
as pebbles & gravel are left behind.
 Protect underlying layers of fine particles from
further deflaction by capping them.

DEFLACTION HOLLOW
 A depression crested by wind erosion .
 Most deflaction hollows are small ,some may
exceed 1.6 km in diameter.

ABRASION
 It is also known as “CORRASION”.
 The blown particles strike against up standing
masses & causes erosion by mechanical wearing of
rock .
 Process same as “SANDBLASTING”.

FACTORS ARE----
 The strength of the wind .
 Persistence of wind .
 Hardness of the blowing sand grains .
 Angularity of the blowing sand grains .
 The resistance of the rock being abraded.

FEATURES PRODUCED BY
ABRASION
Ventifacts
Yardangs
Pedestal rock
Zeugen

An individual rock that is pitted,grooved or
streamlined through wind abrasion .

YARDANGS :-
 Ridges that are sculpted & streamlined by wind
abrasion and deflaction .

Pedestal rock
Wide rock-cap standing on a slender rock
column.

ATTRITION
 The rock particles not only abrade the exposed
bad rock but they themseleves are also abraded by
colliding against one another
 This produces a rounded appearance of individual
fragments .
Adds a “frosted” appearance to sand grains
Rounding of
grains
•

WAYS IN WHICH EOLIAN SADIMENT IS TRANSPOTED
TRANSPORTATION
SALTATION
MEDIUM SIZED
PARTICLES
O.O5 mm TO 2.0
mm
THROUGH A
SERIES OF
BOUNCES
SUSPENSION
FOR SILT & CLAY
LIGHT & FINE
LOOSE MATERIAL
KEPT IN AIR
DUST CLOUD
SURFACE CREEP
PARTICLE OF LARGE
SIZE
THROUGH ROLLING &
CREEPING

WAYS IN WHICH EOLIAN SADIMENT IS
TRANSPOTED

DEPOSITION
When velocity of wind checked then deposition started .
Forms aeolian deposits .
DEPOSITION
SAND SEAS
VAST REGION
ENORMOUS QUANTITIES OF
SAND RESULT IN A WIDE
VARIETY OF DUNE TYPE .
EX.- SAND SEA IN SAHARA
DESERT
SAND SHEETS
HORIZONTAL TO
SEMIHORIZONTAL BODIES
OF SAND
IT EXHIBIT LITTLE OR NO
SURFACE TOPOGRAHPHY.

SAND DUNE’S COMPONENTS &
MIGRATION
BACKSLOPE-The gradual slope of a dune that faces the prevailing winds.
CREST-The highest point of a dune.
SLIP FACE- The steep slope that lies on the leeward side of a sand dune.

SAND DUNES & IT’S TYPES
 A hill made of sand formed by aeolian processes .
 Form due to intrection with the wind .
 The area covered by extensive sand dunes is
known as DUNE FIELD.
 The valley or the low area between the dunes is
called a SLACK.

LOESS
 Windblown silt and clay Deposits far from their source
 „ Soils on Loess Deposits are some of the most fertile in the
world

SUMMARY & CONCLUSION
 Wind processes are typically referred to as eolian processes,
which produce eolian land forms.
 one third of the land on our planet is characterized as arid or
semi arid.
 Wind action can be divided into three parts EROSION,
TRANSPORTATION and DEPOSITION.
 Wind mostly moves loose material
 Features are –Yardang , Ventifacts ,Pedestal rock , Loess etc...
 Sand dunes depend on strength and steadiness of wind
and abundance of sand
 Windblown silt is called loess

REFERENCES
 Principle of physical Geology by ARTHUR
HOLMES.
 “GEOLOGICA” Earth’s geologycal past.
 Discovering physical Geography by Alan
 Introduction to phisical Geology by A.K. Datta.
 Theory and problems of introductory Geology by
Richard W Ojakangas.

F.A.Q.
 1.Where is wind erosion is most effective ?
 Ans. It is most effective where there is a lake of vegetation and
moisture.
 2.What is transported by wind - clay,silt,sand,or gravel ?
 Ans. the fine grained particles clay and slit are most easily transported
by wind. Some sand is also moved as evidenced by sand dunes.
Coarser sediments remains behind.
 3.What is a lag gravel ?
 Ans. The coarse sediment left behind where wind has removed the fine
grain sizes.
 4. What effect will a lag gravel have on wind erosion ?
 Ans. It will prevent further removal of fine sediments from beneath the
gravel layer.
 5. Are sandstorms common ?
 Ans. NO . Sand is rarely lifted more than 1 or 2 m off the ground . Most
sandstorms are rarely duststrome composed of clay and silt sized
particles.

F.A.Q.
 6. What causes wind ?
 Ans. As the sun heats the air in a given area ,it expends and rise . As this this occurs
,denser and cooler air moves into the area . As it moves in , wind is the result.
 7. What factor most affect the ability of wind to carry sediment of different grain sizes?
 Ans. The velocity of the wind . The higher velocity, the larger. The particle that can be
carried. However the maxium size that can normaly be carried is sand unless tonudo or
huricane is present.
 8. What is ventifact?
 Ans .A ventifact is a stone eroded by the sand-blasting effect of the
wind.smooth,inclined,and polished face or facets are characteristic.
 9 . what is a deflation basin?
 ANS.A deflation basin is a shallow basin eroded by wind in areas of dry ,fine-grained
sediment.some deflation basin in desert areas can be tens of kilometers long and tens of
meter deep.
 10. what is loess,and whats is it composed of ?
 ANS.Loess is a term applied to widespread,thick deposits of wind-blown silt.It generally is
made up of quartz and feldspar.Calite is commonly added after deposition.

 11.How far can wind –blown dust be transported?
 ANS.Very far.Fine volcanic ash,for example,can be thrown several kilometer high by a
volcanic eruption and can circle the earth for year .when the volcano krakatoa in the east
indies exploded in 1883,volcanic ash rose to 130,000ft and circled the earth for years
,even making the days slightly durker then usual.
 12.where does loess form?
 ANS.In two main places,either down wind from ablating glaciers or down wind from
deserts examples of glacial loess are found in the mississippi and missouri. River valleys
of the upper midwest .Desert related loess exists in north western china,probably derived
from the gobi desert of central asia.
 13.How large can sand dunes becomes?
 ANS.With a sources of abundant sand and stronge, stable wind,dunes can reach heights
of 250m,as in the saudi arabian deser.
 14.Are sand dunes stationary?
 ANS.some are ,if they have been stabilized by vegetation .However,most dunes are
actively moving down wind,or migrating. Rates vary from lees than a metre a year to tens
of meters , and some may migrate much faster.
 15. Is the sand in sans dunes well sorted or poorely sorted?
 Ans. Well sorted. The fine slit and clay are generaly carried out of the dunes area by the
wind,and coarser grains are left behind. The sand itself is better sorted than river or beach
sands and is generaly fine to medium grained sand.

ASSIGNMENTS
Located the arid & semi arid-region on map of India.
Located the arid & semi arid-region on map of World.

ASSIGNMENTS
 Find the place where sand seas occurs in the world .
 Find out the data about sand dunes on Mars and prepare
a brief report.
 Write the name of the major desert present in all over the
world.

QUIZES
1.Which of the choices below is not a defining
characteristic of a desert?
A)high temperature
B)precipitation exceeds evaporation
C)shifting sand dunes
D)none of the above are defining characteristics of
deserts.
2.Which of the following is a common feature of
desert regions?
A)flash floods
B)slow chemical weathering
C)internal drainage
D)all of these.

3.A very flat surface underlain by a dry lake bed of hard,
mud-cracked clay is called
A)plateau. B)mesa. C)bajada. D)playa.
4. Rocks with flat, wind-abraded surfaces are called
A)ventifacts.B)pediments C)blow-outs.D)barchans.
5. The erosion of sand, silt, and clay from the land surface is
called
A)depletion. B)deflation. C)deposition. D)transport.
6.Which of the following is not a type of sand dune?
A)Transverse B)Barchan
C)Parabolic D)all of these are types of sand dunes
7.A surface layer of closely packed pebbles found in desert
areas is
A)ventifact. B)bajada C)desert
varnish D)desert pavement.

8.Plants living in desert regions
A)are able to survive when it rains.
B)are adapted to low moisture levels.
C)often have small leaves with waxy coatings.
D)all of these
9.A sand dune that is convex in the downwind direction is
A)a transverse dune. B)a parabolic dune.
C)a barchan dune. D)a longitudinal dune.
10.Sand dunes have been observed on
A)Mars. B)Uranus. C)the Moon. D)Venus
11.Deposits of windblown silt and clay are called
A)dunes. B)loess. C)clay. D)silt.
12.Most dunes move only
A)10 to 15 meters per year. B)30 to 100 meters per year.
C)1 to 2 kilometers per year. D)none of these

13.In the United States, Death Valley is a desert because
A)it is the location of a secret flying saucer base.
B)it is very hot.
C)it is below sea level.
D)it is in the rain shadow of the Sierra Nevada mountains.
14.what is a feature produced by abrasion-
A) Hamada b) lag deposits c) Yardang d) none of these
15. which feature has a wide rock cap standing on a slender
rock ?
A) ventifacts B)pedistal rock c) sand dunes D)Hamada
16. The erosion of sediments by mutual collision is known as
A)attrition B)abrasion C)deflation D)none of these
17. The methord of transportation through rolling and creeping is
known as-
A) Traction B) saltation C)suspension D)none of these

18. what part of the land in the Earth is covered with arid and
semi arid region ?
A)1/4 B)1/3 C) 3/4 D)1/2
19. The highest point of sand dunes is called
A)crust B)crest C)butte D)pinnacle
20. the gradual slope of a dune that faces the prevailing winds.
A) Back slope B)slip face C) lee slope D) NOT

Aeolian process and landform by shivam soni B.Sc student of Department of Applied Geology Dr. Harisingh Gour University, Sagar Universityfinal ppt 2007

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