1. Landforms By Wind: Geological Work Of Wind Dr. Prabha Joshi
Department: B.E. Civil Engineering
Subject: Engineering Geology
Semester: III
Teaching Aids Service by
KRRC Information Section
Teaching Aids Service by KRRC Information Section

2. Geological work of wind
Air in motion is called Wind.
Wind is an effective agent of erosion, transportation and deposition in desert regions.
Wind also moves loose sediment in a variety of other Environments.

3. Wind Erosion Deflation Deflation: Latin- deflare= to blow away.
Removal of particles of dust and sand by winds, this is the main process of erosion in deserts
Low spots carved out by wind erosion
High elevations are left due to vegetative stabilization

4. Blowouts and Oasis
Deflation may cause removal of sand from a particular location to such an extent that a big depression is created.
Sometimes these depressions intersect the water table and get partially filled up with water and called oasis.

5. Yardangs
These are elongated low-lying ridges forming overhang above local depressions.
The trend is parallel to prevailing winds. They commonly occur in groups.
Form in areas of alternating hard and soft rocks.

6. Pedestal or Mushroom rock
Base of a rock is weathered and eroded more quickly due to sand blasting
Sand grains can only be picked up a couple of feet

7. Natural arch Typically formed by a combination of wind and water
Narrow ridges are formed and the softer substrata is weathered first, forming a bridge/arch overhead

8. Arches National Park, Utah

10. Ventifact
These are small rock fragments created by wind erosion, showing one, two or more wind polished surfaces.
Wind carries fine particles that work like a sand blaster (i.e. silt, clay, and ice particles)
The windward face of the rock is flattened and smoothed
Usually pebble to cobble sized

11. Dreikanter A type of ventifact that has three ridges
Multiple faces have been formed by either a changing prevailing wind or movement of the actual rock being weathered

12. Desert pavement or Hammada
It is the Bare rock surface in a desert formed when wind carries finer, more lightweight particles such as sand away
Large particles are left behind and protect from further erosion

13. How does Wind transport sediment?
Saltation
• Sediments too large or heavy to be carried in suspension by water or wind are dropped and picked up again and again during transportation process.
It is therefore a process of sediment transport in series of jumps.
Suspension
Silt- and clay sized particles constitute most of this load, held aloft for many miles

14. Deposition by Wind
Loess: Loess is unconsolidated, unstratified and porous accumulation of yellowish, fine grained silt and clay sized particles.
Formed by glaciers.
Carried and deposited by wind.

15. Loess is a deposition of silt, with a little amount of sand and clay
Loess is a deposition of silt, with a little amount of sand and clay. It appears yellowish or brownish in color. Many a times, wind action is responsible for formation of loess. Glacial activities also contribute to formation of a loess.

16. Sand Dunes Variously shaped deposits of sand grade particles.
Deposited by wind
Leeward side (slip face) has a steeper slope
Windward side is more gradual
Leeward
Windward

17. Barchan Dune Crescent shaped dunes Concave side is the leeward side
Formed from a unidirectional wind
cusp
crest

18. Dunes

19. Transverse dunes
A dune that elongates perpendicular to the prevailing wind
Caused by a combination of wind directions

20. Longitudinal (Seif) dunes
Longitudinal dunes (also called Seif dunes, after the Arabic word for "sword"), elongate parallel to the prevailing wind. Seif dunes are sharp-crested and are common in the Sahara.
A seif dune is a steep sided ridge that extend in a sinuous or s-shaped outline.
Both the sides of a sigmoidal dune are steeply inclined at angles of

21. Parabolic dunes Crescent shaped dunes
Concave side is the windward side
Found in coastal deserts
Arms of the crescent lag behind because they are held in place by vegetation

22. Ergs
Huge dune fields

23. Ripple marks
Miniature dunes within a dune (not more than 2 inches tall)
Formed by wind
May form from cross winds and appear to be traveling in a different direction than the large dune

24. Sunlight casts shadows on sand dunes in White Sands National Monument, New Mexico. These dunes are made of pure gypsum, a soft mineral left behind when water evaporates from a nearby lake.

25. Three motorcyclists drive around rock formations in Zion National Park, Utah. The rock formations are actually ancient sand dunes. Weathering from wind and water will eventually turn Zion's rock formations to sediment and dust again.

26. An aerial photo captures sand dunes under shallow water near the Bahamas, in the Caribbean Sea. These dunes are created by water currents. Wind currents form sand dunes on land.

27. Sand dunes form on ancient salt beds in Baja California, Mexico
Sand dunes form on ancient salt beds in Baja California, Mexico. Wind erosion moves the sand dunes across the landscape. The curving dunes "point" the way the wind is blowing.