Why do sand dunes move?
Show answer & explanation
Answer: Wind carries grains over crest
Underground water pushes sand — Wrong. Water can affect sand, but dune migration is driven by wind blowing grains up the windward side and over the crest.
Animals disturb the surface — Wrong. While animals leave tracks, they don't cause dune migration. Wind is the dominant force moving tons of sand.
Wind carries grains over crest ✓ — Correct! Wind blows sand grains up the gentle windward slope. At the crest, grains cascade down the steep slip face. This saltation process moves the entire dune forward! Some dunes migrate 30+ feet per year, burying forests and roads. Dune shapes reveal prevailing wind directions.
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