One of my favorite sand dune facts concerns how they move. I had always assumed that a crescent (barchan) dune moves forward from fat middle first, trailing the pointy ends behind it like two tails. But it’s the opposite! The wind blows the pointy points forward more easily, because there’s less mass there. The higher sand follows down because of gravity, and over the course of time, the sand dune moves, the smaller crescent points leading the way.
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