Hoping in the wind.Hopping in the wind The details of how the wind carries sand from place to place have important consequences for the study of processes such as wind-driven soil erosion, sediment transport on Mars, the formation of sand dunes sand dune Hill, mound, or ridge of windblown sand or other loose material such as clay particles. Dunes are commonly associated with desert regions and seacoasts, and there are large areas of dunes in nonglacial parts of Antarctica. and the wearing away or polishing of rocks. Various wind-tunnel studies and other investigations over the last few decades have shown that particles the size of typical sand grains travel in the wind principally by hopping, or saltation saltation /sal·ta·tion/ (sal-ta´shun) 1. the action of leaping. 2. the jerky dancing or leaping that sometimes occurs in chorea. 3. saltatory conduction. 4. . The wind whisks these particles into the air, carrying them for a short distance. At the end of a hop, the grains hit the sand bed, rebounding or splashing out other grains to be carried along further by the wind. In the Aug. 12 SCIENCE, Robert S. Anderson of the University of California, Santa Cruz The University of California, Santa Cruz, also known as UC Santa Cruz or UCSC, is a public, collegiate university, one of the ten campuses of the University of California. , and Peter K. Haff of the California Institute of Technology California Institute of Technology, at Pasadena, Calif.; originally for men, became coeducational in 1970; founded 1891 as Throop Polytechnic Institute; called Throop College of Technology, 1913–20. in Pasadena describe computer simulations that closely mimic the behavior of blowing sand. Their analysis shows the effect of saltating grains on wind velocity The horizontal direction and speed of air motion. and demonstrates the importance of splashing in keeping sand grains in the air. |
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