Dunes

Wind-shaped ridges of loose sand, actively migrating rather than fixed in place — diagnostic features are the asymmetric profile (a longer, gentler windward slope facing the prevailing wind, and a shorter, steeper leeward slip-face on the far side) and the crescent or wave-form ridge patterns wind produces, plus the absence of anything anchoring the sand permanently in place.

Hot Desert

Wind-shaped sand ridges stretch to the horizon; footing loose and shifting, no reliable landmark holds still.

Arid

dunes desert arid 01

Bare, sun-bleached sand, nothing green in frame — reach for this when the scene should feel hostile or empty.

Location: Murzuq, southwest Libya

Tropical

dunes desert tropical 01

Same landform, humid haze and a green line visible beyond the dunes — reach for this when dunes are a waypoint, not a threat. Typically, the features are seasonal, coinciding with the wet seasons.

Location: Lençóis Maranhenses, Brazil

Arctic / Subarctic

dunes desert arctic subarctic 01

Same ridgeline shape, snow scoured into the same wind-formed pattern sand would take — reach for this to make the point that the landform is what’s constant, cover and climate are what change.

Location: The Great Kobuk Sand Dunes, Kobuk Valley National Park, Alaska