3.2 W IND E ROSION AND D EPOSITION Kavya, Olga, Ivy, and Grace

Questions For You!!! What are the three different processes of erosion by wind? Why is loess found very far away from its source?

F UN F ACTS Wind erosion causes more than half of the soil loss in the U.S.A. per year. In the Great Plains, five million acres are damaged by wind erosion annually. Landmarks such as Bryce Canyon, the Grand Canyon, and others are formed partially by wind erosion.

T HE PROCESS OF W IND EROSION Saltation is the movement of sand or other sediments by short jumps and bounces that is caused by wind or water. Deflation is a form of wind erosion in fine, dry soil particles are blown away. Abrasion is the grinding and wearing away of rock surfaces through the mechanical action of other rock or sand particles.

S ALTATION When moving sand grains hit each other it causes other grains of sand to bounce up or fall forward.

D EFLATION Wind removes the top layer of sediment and leaves behind the larger, heavier pieces of rock. In areas where there are few plants the wind may scoop out depressions in the landscape. These depressions are called deflation hollows.

A BRASION Abrasion occurs most often in areas where there are strong winds, loose sands, and soft rocks. When the wind picks up millions of sharp sand grains it creates a sandblasting effect. This effect helps to erode and smooth rocks.

W IND D EPOSITED M ATERIALS Vocabulary Loess- very fine sediments deposited by wind Dune- a mound of wind-deposited sand that keeps its shape even though it moves

L OESS Because wind carries fine-grained material much higher and further than it carries sand, loess deposits are sometimes found far away from their source.

D UNES 1) When the wind hits an obstacle, such as a plant or rock, it slows and drops heavier materials. 2) The material collects creating a new obstacle which causes even more material to be deposited, forming a mound. The original obstacle is eventually buried. 3) These mounds are called dunes and are commonly found in sandy deserts and along the shores of lakes and oceans.

T HE M OVEMENT O F D UNES Dunes move in the direction of strong winds. The gently sloped side faces the wind, which constantly transports material up this side. As sand moves over the crest, or peak, of the dune, it slides down the slip face, creating a steep slope.

A NSWERS FOR YOU Q: What are the three different processes of erosion by wind? A: Saltation, Deflation, and Abrasion. Q: Why is loess found very far away from its source? A: Because wind carries fine-grained material (loess) much higher and further than it carries sand.