Crescent Dune Field

Crescent Dune Field is an original illustration set in Atlantic Sahara, Mauritania. It lies in the tropics, where the climate is hot desert — evaporation far outruns rainfall.

Crescent dunes repeat across a stony plain, each with two thin horns reaching downwind and a steep dark slip face on the concave side. The windward slopes are smooth and shallow. Bare ground shows between separate dunes, and every crescent points the same way.

Why is the dune shaped like a crescent?

A barchan forms where there is steady wind, one dominant direction and not quite enough sand to cover the ground. Grains climb the gentle windward slope, spill over the crest and avalanche down the steep face; the thinner edges travel faster, which is what draws the horns out. Bare ground between them is the diagnostic — an unlimited sand supply would merge them into ridges.

Terpano is a free daily geography puzzle. You study one original illustration, place a pin on a borderless terrain map, and see how close you were. There is no account and no sign-up; progress stays in your own browser. It plays in 11 languages.