wind landforms.pptx

it is a complete presentation of the action of wind landform characteristics.

1. wind landform characteristics ACTION OF

2. Group E Group Members: Ellin Sumaia Zaman (2012256158) Arifa-Tul-Rayhana (2012156182) Nafis Foysal (2010656145) Md. Ohid Zaman (2010656187) Md. Rakib Mia (2010856107) Most. Rotna Khatun (2012056116) Md.Zahid Hossain (2010856126) Urmi Roy (2012256135)

3. LAYOUT Introduction Factors of erosion due to wind Process of erosion Transportation work of wind Erosional landforms due to wind Depositional landforms Conclusion

4. LAYOUT Wind Wind is moving air and is caused by differences in air pressure within our atmosphere. Air under high pressure moves toward areas of low pressure. The greater the difference in pressure , the faster the air. Wind transports small particles, such as silt and clay, over great distances, even halfway across a continent or an entire ocean basin. Particles may be suspended for days. Factors of erosion due to wind Wind velocity Tools of erosion Variation of temperature Composition of rock Low precipitation Nature of vegetation

5. LAYOUT Transportation work of wind According to Bagnold(1974) and Warren(1979), Saltation: usually occurs in the moving air layer that’s closest to the earth surface. when wind velocity exceeds the threshold velocity, the dust is lifted up by the aerodynamic force at an angle of 6-12 degrees to the wind flow and falls back to the ground on its own propagation stream. Surface creep: surface creep occurs when soil particles larger than .5 mm in diameter are dragged over the surface of the land because they are too heavy for the wind to lift. as the particles roll and along the surface , they bump into each other. Suspension: when materials are very less than 0.15mm in diameter they can be easily picked up by the wind example Sahara desert.

6. LAYOUT Process Of Erosion Deflation Deflation occurs in rocky areas when air enters into crack in rock. This air is trapped in cracks by the rising tide, as waves crash against the rock the air inside the crack is rapidly compressed and decompressed causing cracks to spread and pieces of rock to break off. Compression is one of the main processes that result in the creation of caves. Abrasion Abrasion is when rocks and other materials carried by the sea are picked up by strong waves and thrown against the coastline causing more material to be broken off and carried away by the sea. Attrition Attrition is when material such as rocks and stones carried by waves hit and knock against each other wearing them down. As these materials are worn down sand and rounded beach pebbles are formed.

7. LAYOUT Erosional landform Deflation hollows Ventifact Mushroom Inselberg Demoiselle Zeugen Yardang Desert pavement Wind bridge and window

8. LAYOUT Erosional landform Characteristics Deflation Hollows/Blowouts: removal of loose particles from the ground by the action of wind. And, deflation causes a shallow depression by persistent movements of wind, they are called as deflation hollows.

9. LAYOUT Mushroom or Pedestal rock also known as a rock pedestal or gour . is a common mushroom-shaped landform. in dry areas with little vegetation to obstruct aeolian particle movement. frequent high winds. and a steady but not excessive supply of sand. Yardangs define as spectacular stream lined, sharp and sinuous ridges. extend parallel to the wind . example: Boukou area near the Tibesti Mountains of Chad.

10. LAYOUT Zeugen also called perched or mushroom rocks related to yardangs where sand laden wind is funneled by topography, even hard rock maybe fluted, grooved, pitted, and polished by sand blasting. Windy Point, near Plam Springs, in the Mojave Desert, California. Ventifacts cobbles and pebbles on stony desert surfaces often bear faces called ventifacts the number of edges or keels they carry is sometimes connoted by the German terms - Einkanta - Zweikanter -Dreikanter

11. LAYOUT Demoiselle rock pillars which stand as resistant rocks above soft rocks as a result of differential erosion of hard and soft rocks. Inselberg a body of rock resistant to erosion, such as granite, occurring without a body of softer rocks, is exposed by differential erosion and lowering of the surrounding landscape. Example: Olga rocks in central Australia.

12. LAYOUT Desert pavement formed by surface of angular, interlocking fragments of pebbles, gravel in arid areas. it also called reg (western Sahara) serir(eastern Sahara) gibber(Australis) Wind bridge and windows sometimes the holes are gradually widened to reach the other end of the rocks to create the effect of a window window bridge are formed when the holes are further widened to form an arch-like feature.

13. LAYOUT Depositional erosion Along sea line Atlantic coast of the United States from Massachusetts to Florida Along river valleys in arid regions Sand dunes , USA , river valley in Egypt, large plains in America Desert area Almost everywhere in desert Position of depositional landform

14. LAYOUT Wilson, Cook and warren made a classification of wind storage landforms based on their shape and volume. They are; Ripple Ripple is an depositional of wind waves with a height of 0.001 to 20 cm and a wave length of 4 cm. Drass Usually 1 to 3 kilometers wavelength and 30 to 200 meters heigh large size sand piles are called drass . Sand dune A sand dune is usually 40 meters or 200 meters long and has a height of 1 to 30 meters. Sand dunes of different shapes and sizes are found in different desert regions. Types of sand dune Longitudinal sand dune Blowout dune Parabolic dune Star Seif Shit and strain Transvers dune Barchan Dome dune Reversing dune

15. LAYOUT Types of sand dune Blowout dune Barchan dune Blowout dune Barchanoid ridges dome dune Transvers ridges

16. LAYOUT Loess Plains: Winds deposit light and soft soil over a large area like a blanket, these are known as plains of Loess. ‘Loess’ is a word of German language which means yellow colour , porous soil with very soft particles. Generally, these particles are of the same size. This soil does not have layers and it is friable. When we press it crumbles easily. During rainfall it becomes very sticky, on the other hand in summer it becomes very dry. Loess is found in China, Europe, North America, South America and Africa. The name “Yellow river” in China is also given on the basis of their soil because when it mixes with river water, water appears to be yellow in color.

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