1. Eolian Processes and Arid Landscapes
Current News & Weather
Wind Processes and Landforms
Loess Deposits
Desertification
Streams in Drylands
Weathering of Arid Landscapes
For Next Class: Read Chapter 16

2. Eolian Processes
Eolian means wind.
Eolian processes include erosion, transportation, and deposition accomplished by wind.
Because air is much less dense than water, wind is unable to move materials as effectively as water.
Over time, wind can do enormous work.

3. Eolian Transport of Dust and Sand
Suspension: grain size < 0.2 mm
Saltation: (80%) grain size > 0.2 mm
Surface creep: (20%) grain size too large for saltation
Figure 15.2

4. Dust Storms Engulf Phoenix, AZ
Figure 15.3

5. Sand Movement and Wind Velocity
Figure 15.4

6. Eolian Erosion
List and discuss the two principal wind erosion processes

7. Two principal wind-erosion processes: deflation and abrasion
Eolian Erosion
Two principal wind-erosion processes: deflation and abrasion
Deflation: removing and lifting individual loose particles
Abrasion: grinding rock surface by the “sandblasting” action of particles captured in the air

8. Yardangs
Rocks exposed to eolian abrasion appear pitted, fluted, or polished.
Yardangs refer to large scale streamlining rock structures (formed by deflation and abrasion) that are aligned parallel to the most effective wind direction.
Yardangs can range from meters to kilometers in length and up to many meters in height.

9. A Field of Yardangs
Figure 15.6

10. Desert Pavement
Desert pavements are called gobi in China, and gibber plain in Australia.
Figure 15.7

11. Eolian Depositional Landforms
Only 10% of desert areas are covered with sand.
Desert pavements predominate across most subtropical landscapes.
Sand grains generally are deposited as transient ridges or hills called dunes.
In North Africa, an extensive area of dunes is called sand sea.

12. Erg, or Sand Sea
Figure 15.8

13. Barchan Dunes
Figure 15.9

14. Star Dune in Namibia
Figure 15.10

15. Dune Profile

16. Three Classes of Dune Forms
Crescentic (crescent, curved shape)
Linear
Star

22. Preventing Sand Transport
Figure 15.12

23. Loess
What is loess and where are the primary loess deposits around the world?

24. Loess Deposits
The retreat of the Pleistocene glaciers approximately 15,000 years ago exposed large glacial outwash deposits of fine-grained clays and silts.
These materials were blown great distances by the wind and re-deposited in unstratified deposits, which are called loess.
Loess deposits are fertile soils because of deep soil depth and the well drained characteristics of Earth’s “breadbasket” farming regions.
Loess deposits have excellent structural strength.

25. Loess Regions of the World
Figure 15.13

26. The Loess Plateau, China
Figure 15.14

27. Desertification
What is desertification and what locations are most susceptible?

28. Arid and Semiarid Climate Regions
Figure 15.15

29. Desertification
Figure 15.16

30. Combating Desertification in China
Figure 15.17

31. Drying Lake Urmia in Iran
Figure 15.18

32. Badwater Alluvial Fan, Death Valley, CA
Figure 15.20

33. Sandstone Weathering and Alcoves
Figure 15.24