1. Notes for Section 8.2—Wind

2. Wind Wind causes erosion by transporting sediments uphill as well as downhill. Wind can modify and change landscapes in arid and coastal regions.

3. Suspension and Saltation Wind can move sand on the ground in a rolling motion. Suspension is a method of transport by which strong winds cause particles to stay airborne for long distances. Saltation is another method of transport that causes a bouncing motion of particles. Saltation accounts for most of the sand transport by wind.

4. Deflation The lowering of the land surface that results from the wind’s removal of surface particles is called deflation. It is a major problem in many agricultural areas of the world.

5. Abrasion Abrasion occurs when particles such as sand rub against the surface of rocks. In wind abrasion, wind picks up materials such as sand particles and blows them against rocks and other objects. Windblown sand causes rocks to become pitted and grooved. Rocks shaped by wind-blown sediments are called ventifacts.

6. Deposition Wind deposition occurs in areas where there are changes in wind velocity. As wind velocity decreases, some of the wind-blown sediment can no longer stay airborne, and it drops out of the airstream to form a deposit on the ground.

7. Dunes Dunes form when sand particles accumulate where an object, such as a rock, landform, or piece of vegetation, blocks the particles’ forward movement. Sand continues to be deposited as winds blow in one general direction. Over time, the pile of sand develops into a dune.

8. Dunes All dunes have a characteristic profile. The gentler slope of a dune is located on the side from which the wind blows (windward side). The steeper slope is on the side protected from the wind (leeward side). The height of a dune is determined by the velocity of the wind above the ground surface.

9. There are 4 major types of dunes: 1. Barchan dunes: Solitary, crescent- shaped dunes that form in flat areas where there is little sand or vegetation. They are the most common type of dune.

10. There are 4 major types of dunes: 2. Transverse dunes: Formed where there is plenty of sand, little vegetation, and strong, steady prevailing winds (deserts). They form a series of long ridges that are perpendicular to the direction of the wind.

11. There are 4 major types of dunes: 3. Parabolic dunes: form between clumps of plants in humid areas, and have a characteristic U-shape. They are common on coastlines and beaches.

12. There are 4 major types of dunes: 4. Longitudinal dunes: common in areas where there is limited sand available. Strong prevailing winds shape them parallel to the wind direction

13. Migration Dune migration is caused when prevailing winds continue to move sand from the windward side of a dune to its leeward side, causing the dune to move slowly over time. As long as winds continue to blow, dunes continue to migrate.