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

EROSION TRANSPORTATION DEPOSITION

WIND ACTION CAN BE DIVIDED INTO THREE

PARTS:-

WHY IN HUMID

REGION EXCEPT

ALONG SEASHORE

WIND EROSION IS

LIMITED?

WHY????

Due to the prevalent cover of

grass & trees .

Also by the binding action of

moisture in the soil.

EROSSION

TYPES OF EROSION

DEFLACTION ABRASION ATTRITION

EROSION

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

DEFLACTIONDEFLACTION

Desert pavement

Deflation hollow

DEFLACTION CAUSES

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.

DESERT PAVEMENT

DEFLACTION HOLLOW

A depression crested by wind erosion .

Most deflaction hollows are small ,some may exceed 1.6 km in diameter.

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”.

ABRASION

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

•

TRANSPORTATION

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

DEPOSITION

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.

When velocity of wind checked then deposition started .

Forms aeolian deposits .

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.

TYPES OF SAND DUNES

TYPES OF SAND DUNES

TYPES OF SAND DUNES

TYPES OF SAND DUNES

TYPES OF SAND DUNES

TYPES OF SAND DUNES

TYPES OF SAND DUNES

TYPES OF SAND DUNES

LOESS

Windblown silt and clay Deposits far from their source

„ Soils on Loess Deposits are some of the most fertile in the world

THE PROCESS OF EOLIAN SORTING

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.

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.

ASSIGNMENTS

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