The wind is just strong enough to move the sand grains which were sorted by size by the wind. Heavier grains were left in place where as smaller grains were carried away. These grains kept moving till they were concentrated in one place usually up a hill. The grains climb the flat slope on the windward side and then fall off the steep side. The dunes may migrate slowly as this process continues, the grains at the upwind side climb the dune with the help of the wind and then fall down the downwind side.<span>
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The reason both of these are valid scientific hypotheses is because A) scientists with different educational backgrounds may put forth different hypotheses to explain the same data.
This approach in science is vital in making progress and has helped to explain many phenomena in the past. When scientists explain data using different approaches, they come to a more comprehensive conclusion.
Answer:
An <u>Earthquake</u><u> </u>is one of the most dramatic triggers of sudden mass movements.
