Crescent-shaped dunes around Lagoa dos Barros on Brazil's Atlantic coast, seen from the ISS.

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Preparing the 3D view

Preparing lighting and the first complete frame…

Model scale

60 × 40 m selected landform. relief ×2. wind points +x.

Barchan: deposited sand, a gentler windward slope and a steeper lee slip face. Migration translates the chosen shape downwind without assigning a rate.

How to read these results

Play follows enlarged hopping grains downwind. The static shape is not a sediment-transport simulation. Many deserts have rock or gravel surfaces; a dune requires an available sand supply.

Wind landforms

Explain how wind erodes rock and transports sand, then identify the wind direction from the shape of a barchan dune.

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Why it happens

Wind transports particles by suspension, saltation and surface creep. Where sand supply and wind conditions allow accumulation, deposition builds dunes whose shapes reflect transport and local obstacles.

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Wind shapes barchan dunes beside Lagoa dos Barros, Brazil. The crescent tips point downwind.

Try a comparison

Compare Barchan dune with Yardang ridges; Play follows enlarged grains.

Reading the result

The examples show selected forms and transport directions; dune migration speed requires additional wind and sediment evidence.

A common misunderstanding

Every desert is covered by dunes.

Many deserts expose bedrock, gravel or other surfaces with little loose sand. Dunes require a suitable sediment supply and wind conditions that allow accumulation. Wind can erode one area while depositing material elsewhere, so aridity alone does not determine the landform.

Cases

Exam language

Yardang

An elongated ridge shaped by wind erosion in relatively soft material, typically aligned with the prevailing erosive wind. Abrasion and deflation carve the surrounding grooves. A yardang is an erosional landform, unlike a dune built by deposition.

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Yardangs at Dunhuang, China. Persistent wind erosion shapes elongated ridges in relatively soft rock or sediment.

Barchan

A crescent-shaped dune formed where sand supply is limited and wind mainly blows from one direction. Its horns extend downwind.

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Wind shapes barchan dunes beside Lagoa dos Barros, Brazil. The crescent tips point downwind.

Deflation

The removal of loose surface particles by wind. Fine material may be carried away in suspension, leaving a coarser lag behind. Deflation removes sediment; abrasion is the wearing of surfaces by particles that the wind carries.

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Sossusvlei dunes, Namib Desert. Wind transports loose sand by surface creep and saltation; the dunes record accumulated transport rather than individual grain paths.

Saltation

Transport in short hops or bounces, especially of sand grains moved by wind or flowing water.

Suspension

Transport of fine sediment within moving water or air, kept aloft by turbulence rather than continuously resting on the bed or ground.

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NASA Landsat observation of the Thames estuary. The tidal river widens towards the North Sea; pale water reveals suspended material and shallow coastal water.

Nabkha

A mound of windblown sediment accumulated around a shrub or other vegetation. The plant slows nearby airflow and traps moving grains. Its shape and growth reflect the interaction between vegetation, wind and sediment supply rather than wind direction alone.

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Mesquite in Mojave National Preserve, California. Vegetation traps wind-blown sand and can build a small dune called a nabkha.

Erg

A broad region covered by wind-deposited sand and dunes, often called a sand sea. An erg needs a supply of sand and conditions that allow it to accumulate. Many deserts instead have mainly rocky or gravel surfaces.

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