Barchan

Hey kiddo, have you ever been to the beach and seen those cool sand dunes with curvy shapes that look like they are sitting on top of a hill? Those are called barchan dunes!

Barchan dunes are made of sand that is pushed around by the wind. Kind of like how you push your toys around on the floor with your hands, except the wind does it outside.

Now, imagine the wind only blows from one direction, like from East to West. The sand particles start to move in the same direction as the wind, slowly building up into a small hill shape. As the hill gets bigger, it starts to create a little valley on the other side of it, where there’s actually less sand because it’s all being carried away by the wind.

Eventually, the sand hill gets bigger and bigger until it looks like a half-moon or crescent shape that the wind can’t push over anymore. The wind still blows, but now it’s blocked by the barchan dune.

These dunes are found in deserts like in Egypt, Mongolia, and even the United States! They can be as small as just a few feet or as large as a small mountain.

So that’s what a barchan dune is, a sandy hill that's formed by the wind, and over time it creates a cool crescent shape.