PRESENTED BY:-SHIVAM SONI

GEOLOGICAL ACTION OF WIND

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’.

DEFLACTIONDEFLACTIONDEFLACTION

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

What are the factors

Which influence how rapidly

Abrasion occurs????

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 rockZeugen

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

YARDANGS :- Ridges that are sculpted & streamlined by

wind abrasion and deflaction .

Pedestal rockWide 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 AIRDUST CLOUD

SURFACE CREEP PARTICLE OF LARGE SIZE THROUGH ROLLING & CREEPING

WAYS IN WHICH EOLIAN SADIMENT IS TRANSPOTED

DEPOSITION

DEPOSITION

DEPOSITION

SAND SEASVAST 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 temperatureB)precipitation exceeds evaporationC)shifting sand dunesD)none of the above are defining

characteristics of deserts.2.Which of the following is a common feature

of desert regions?A)flash floodsB)slow chemical weatheringC)internal drainageD)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 calledA)depletion. B)deflation. C)deposition. D)transport.6.Which of the following is not a type of sand dune?A)Transverse B)BarchanC)Parabolic D)all of these are types of sand dunes7.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 regionsA)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 these9.A sand dune that is convex in the downwind direction isA)a transverse dune. B)a parabolic dune.C)a barchan dune. D)a longitudinal dune.10.Sand dunes have been observed onA)Mars.B)Uranus. C)the Moon. D)Venus11.Deposits of windblown silt and clay are calledA)dunes. B)loess. C)clay. D)silt.12.Most dunes move onlyA)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 becauseA)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 these15. which feature has a wide rock cap standing on a

slender rock ?A) ventifacts B)pedistal rock c) sand dunes

D)Hamada16. The erosion of sediments by mutual collision is

known as A)attrition B)abrasion C)deflation D)none of these17. 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)pinnacle20. the gradual slope of a dune that faces the

prevailing winds.A) Back slopeB)slip face C) lee slope D) NOT