wunder beta🏜️ How sand dunes move across a desert
Follow saltation, slip faces, wind regimes, sediment budgets, and repeated measurements to see how dunes migrate across deserts.
What you’ll learn
- Sand begins with a grainExplain how grain size, saltation, ripples, and sediment supply begin dune formation.Dunes start when loose sand is available and wind can move grains in short hops across an open surface.
- Wind builds a duneIdentify windward slopes, crests, slip faces, avalanches, and major dune shapes.Wind carries grains uphill, then gravity moves them down the sheltered slip face, building a recognizable form.
- Why dunes travelUse sediment budgets, wind regimes, dune height, and satellite evidence to explain migration.A dune advances when repeated transport shifts its mass, and its speed reflects size, supply, wind, and interactions.
- Dunes meet the wider worldConnect dune motion with vegetation, infrastructure, dust, Mars, and climate records.Dunes affect people and environments, while their movement preserves evidence about both Earth and other planets.
- Putting the motion togetherTrace one grain through a dune and interpret repeated measurements of landform change.The moving shape of a dune emerges from countless transfers between wind, sand, and gravity.
Questions this course answers
What is saltation?
Saltation is the repeated bouncing movement that carries most dune sand close to the ground.
Why does a desert need an open surface for dunes to form?
Vegetation, moisture, crusts, and rough ground trap or shield grains from the wind.
What is the slip face?
The sheltered side reaches the angle of repose and sheds grains in avalanches.
Which feature usually identifies the downwind side of a simple dune?
The lee side is commonly the steep slope formed by repeated avalanching.
Why can a small dune move faster than a tall one?
A smaller dune contains less sediment per crest length, so the same transport can shift it more quickly.
What do repeated satellite images reveal?
Comparing dates lets researchers measure changing crestlines and dune spacing.
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