Erosion and Deposition by Wind

1. Erosion and Deposition by Wind

2. Erosion and Deposition by Wind State standards: 6.2: Topography is reshaped by the weathering of rock and soil and by the transportation and deposition of sediment.

3. Erosion and Deposition by Wind Students will be able to understand that wind shapes the landscape with the process of erosion and deposition by illustrating and describing these processes in a poster or foldable.

4. Erosion and Deposition by Wind Today we will explore how wind shapes the landscape. We will also discover what features are formed by wind erosion and wind deposition.

5. Erosion and Deposition by Wind During this presentation there will be some questions to check what we have learned today. There will also be some questions to answer as an exit paper.

6. Erosion by Wind How does wind cause erosion?

7. Erosion by Wind • Deflation is the process by which wind removes surface material. • When wind blows over the land, it picks up the smallest particles of sediment. Wind causes erosion by deflation.

8. Deflation moves sediment particles of different sizes in the three ways shown below. Deflation Suspension: Fine particles are carried through air. Saltation: Medium-sized particles skip or bounce. Wind Creep: Larger-sized particles slide or roll.

9. Deflation • This leaves behind larger, angular pieces of sediment. • This remaining sediment is referred to as desert pavement. In the desert, deflation by saltation can remove all the smaller pieces of sediment.

10. Desert Pavement

11. Abrasion • At one time, geologists thought that the sediment carried by wind cut the stone shapes seen in the desert. Abrasion by wind can polish rock, but it causes little erosion. • However, now evidence shows that most desert landforms are the result of weathering and water erosion.

12. Check Understanding • One way wind causes erosion is deflation. What are the two ways wind causes erosion? • The other way is abrasion.

13. Check Understanding suspension saltation What are the three types of deflation? creep

14. Check Understanding • An example of deflation by saltation is desert pavement. What is an example of deflation by saltation?

15. Deposition by Wind What features are created by wind deposition?

16. Wind deposition may form sand dunes and loess deposits. Deposition by Wind

17. Sand dunes are deposits of wind-blown sand. Sand Dunes Over thousands of years, wind sweeps sand into huge, ever-changing dunes

18. Sand dunes come in many shapes and sizes. Some are long, with parallel ridges. Others are U-shaped. Sand Dunes They can be small or very large. Sand dunes move over time.

19. Crescent-shaped dunes form where the wind usually blows in the same direction. Sand Dunes

20. Star-shaped dunes form where the wind direction changes frequently. Sand Dunes

21. In California, sand dunes occur along the coast where rivers have supplied sand to bays, like Humboldt Bay. Sand Dunes

22. Areas of sand dunes also can be found in Death Valley and the Mojave desert. Sand Dunes

23. Loess is fine, wind-deposited sediment that is finer than sand, such as particles of clay and silt. Loess Deposits

24. Loess sediment is carried by the wind in suspension and is sometimes deposited in layers far from the source. Loess Deposits

25. Large loess deposits can be found in central China and in the midwestern United States. Loess Deposits

26. Loess helps to form fertile soil. Many areas with thick loess deposits are valuable farmlands. Loess Deposits Loess is easily eroded by water runoff.

27. Check Understanding • Deposits of wind-blown sand are sand dunes. What are deposits of wind-blown sand?

28. Check Understanding • Sand dunes can form crescent-shaped dunesand star-shaped dunes. What are two shapes that sand dunes can form?

29. Check Understanding • Star-shaped Sand dunes are formed by different wind directions. How are star-shaped sand dunes formed?

30. Check Understanding • Two characteristics of loess deposits are they are fertile and they are easily eroded. What are two characteristics of loess deposits?

31. Wind Erosion is by deflation and abrasion. Review • Deflation can occur as suspension, saltation, or creep. • Abrasion causes little erosion. • Wind deposition can be found in sand dunes or loess deposits. • Sand dunes come in many shapes or sizes. • Loess deposits can be very fertile and erode easily.

32. On your exit paper, write the answer to the following questions: Exit Questions

33. Erosion by Wind How does wind cause erosion?

34. Deposition by Wind What features are created by wind deposition?

35. suspension saltation creep Independent Activity Create a poster (or foldable) on an 8.5” x 11” sheet of paper that illustrates and describes the processes of wind erosion and deposition and the features that are created.