Sandy Deserts of the World: Complete Guide to Erg Deserts & Sand Seas

A sandy desert is an arid landscape where wind-blown sand forms extensive sand sheets, dune fields, or large sand seas called ergs. Sandy deserts are only one type of desert landscape. Many deserts are dominated instead by gravel, exposed rock, salt flats, dry basins, or mixed surfaces. The Sahara is the best-known example of this distinction: only about 25% of its surface is covered by sand dunes and sand sheets.

24 articles in Sandy Deserts (Ergs)

Large sandy deserts develop where three conditions persist together: an adequate sand supply, winds capable of transporting it, and terrain where sediment can accumulate. Vegetation, moisture, crusts, and topography then determine whether individual dunes remain mobile, partly stabilized, or largely fixed.

What Is a Sandy Desert?

A sandy desert is a desert or desert sector in which aeolian sand forms a major part of the visible surface. The term can describe anything from a regional dune system to an enormous erg covering tens or hundreds of thousands of square kilometres.

The presence of dunes does not make every desert a sandy desert. Wind removes fine material from some surfaces and leaves gravel or exposed rock behind. Elsewhere, topographic basins and old sediment sources allow sand to accumulate into thick dune fields.

What Is an Erg?

An erg is a broad desert region dominated by wind-blown sand, usually containing extensive dune fields, sand sheets, or both. The term is commonly translated as sand sea.

An erg is larger and more continuous than an isolated dune field. Its sand may be organized into linear ridges, crescentic dunes, star dunes, compound dunes, or several forms occurring together.

How Common Are Sandy Deserts?

There is no reliable global percentage showing how much of every desert is sandy because desert boundaries and surface classifications differ between mapping systems. The proportions also vary sharply from one desert to another.

The Sahara gives a useful scale. Despite its association with dunes, only about one quarter of the Sahara consists of sand dunes and sand sheets. The remaining terrain includes rocky plateaus, gravel plains, mountains, dry basins, exposed sediment, and oases.

Other deserts contain far larger proportions of sand. The Rub’ al Khali is dominated by a nearly continuous sand-sea system, while deserts such as the Simpson contain enormous fields of parallel linear dunes. Mixed deserts such as the Thar combine dunes with plains, cultivated areas, grassland, and other surfaces.

Is the Sahara Entirely Sand?

No. The popular image of the Sahara as one continuous dune field is inaccurate. Roughly 25% of the Sahara’s surface is sandy, while much of the remainder consists of hamada (rock plateau), reg or serir (gravel surfaces), mountains, depressions, dry valleys, and salt-affected terrain.

Large Saharan ergs still cover enormous areas. Examples include the Grand Erg Oriental, Grand Erg Occidental, Great Sand Sea, and other dune provinces across North Africa. Sandy zones are often concentrated in basins and lowlands where sediment is available for wind transport.

How Sandy Deserts and Sand Seas Form

A large sand sea requires a long-term sediment source and repeated wind transport. Sand can come from weathered sandstone, ancient rivers, deltas, lake beds, alluvial fans, glacial deposits, coastal sediment, or older basin fill.

Wind then sorts and moves exposed sediment. Fine dust can travel far into the atmosphere. Sand grains are heavier and usually remain closer to the ground, moving mainly by saltation and surface creep.

Sand Supply

Many major ergs occur downwind of large sediment stores. The Gran Desierto de Altar receives sand derived partly from Colorado River delta sediments and local sources. The reddish sands of the Nefud are linked to sandstone source material. Large Asian basin deserts receive sediment from surrounding mountains, rivers, and old lake or floodplain deposits.

Closed and partly closed basins are particularly effective at collecting sediment. Rivers deliver material from surrounding mountains, then lose water through infiltration and evaporation. Once exposed, suitable grains can be reworked by wind.

How Wind Moves Sand

According to the U.S. Geological Survey, wind-blown sand typically moves up the gentler windward side of a dune by saltation and creep. Sand accumulates near the crest. When the slope becomes too steep, grains avalanche down the lee-side slipface.

Repeated transport and avalanching cause the dune to migrate. The rate can range from barely measurable movement in large stabilized systems to many metres per year in smaller active dunes.

Wind Direction and Dune Shape

The direction and variability of wind strongly influence dune geometry. A persistent wind from one direction commonly favors crescentic or transverse forms. Two dominant wind directions can build long linear ridges. More complex multidirectional wind regimes can produce star dunes.

Topography, sand availability, vegetation, moisture, and pre-existing dunes modify these patterns, so one sand sea can contain several dune types.

Why Some Dunes Become Stable

Not all dunes migrate freely. Vegetation, soil crusts, moisture, salt or mineral cementation, and limited sand supply can stabilize a dune partly or almost completely.

The Badain Jaran Desert contains exceptionally high stabilized mega-dunes. The Gurbantünggüt Desert provides another example: winter snow and spring moisture help support vegetation and biological crusts that anchor much of its sandy surface.

Main Dune Types in Sandy Deserts

The U.S. Geological Survey identifies five basic dune shapes: crescentic, linear, star, dome, and parabolic. Compound and complex dunes can combine these basic forms at much larger scales.

Star Dunes

Star dunes form where winds arrive from several directions. Instead of migrating mainly in one direction, sand accumulates vertically around a central dune mass.

UNESCO records a stabilized mega-dune in the Badain Jaran Desert with about 460 m of relative relief. The desert contains a dense concentration of mega-dunes together with numerous interdunal lakes.

Linear Dunes

Linear dunes can extend for extraordinary distances. USGS material notes that individual linear ridges may exceed 160 km in length. They commonly occur as sets of parallel ridges separated by sandy, gravelly, or rocky interdune corridors.

The Simpson Desert is one of the clearest large-scale examples. Its parallel red ridges extend across much of central Australia and create a highly regular desert landscape visible in satellite imagery.

Sand Color, Grain Size, and Interdunes

Desert sand varies widely in color and mineral composition. Red and orange sands can develop iron-rich coatings, while pale sand commonly contains a larger proportion of quartz or other light-colored minerals. Gypsum can create very pale or white dune fields in some deserts.

Grain size affects dune behavior. Fine and medium sand is readily moved by wind and can form well-defined ripples and slipfaces. Coarser material requires stronger winds and commonly remains closer to the surface.

Interdune Surfaces

The terrain between dunes can differ sharply from the dunes themselves. Interdunes may consist of hard gravel, bare sediment, salt crust, clay, vegetation, or temporary water.

The Badain Jaran Desert is especially unusual because many large dunes surround interdunal lakes. In the Rub’ al Khali, dunes are frequently separated by sabkhas, or salt-encrusted flats.

Major Sand Seas and Sandy Deserts of the World

The table below compares several major sandy desert systems. They are not presented as a strict size ranking because published boundaries often differ and some entries describe entire deserts while others describe individual ergs or dune provinces.

Sandy Deserts by Region

North America

Africa

Arabia and Oman

South Asia, Türkiye, and Iran

China and Inner Asian Basins

Australia

Sandy Desert Comparison

Life in Sandy Deserts

Sandy deserts can support plants and animals even where vegetation appears sparse. Dune crests, slipfaces, interdunes, depressions, and dune margins create different microhabitats with varying wind exposure, temperature, and moisture.

Ephemeral plants can germinate rapidly after rainfall or snowmelt. Deep-rooted shrubs may stabilize dune margins and create shade. In the Gurbantünggüt, winter snow contributes to a short spring period when vegetation becomes more active.

Animals also use sandy terrain selectively. Rodents burrow into dunes, reptiles exploit warm and sheltered surfaces, insects occupy loose sand and vegetation patches, while larger mammals often move along firmer interdunes or desert margins.

Wildlife distribution is therefore rarely uniform across an erg. A vegetated interdune or temporary wet depression can support far more life than an exposed dune crest only a short distance away.

Sandy Desert Landscapes Beyond Dunes

Large sand seas contain more than dune crests. Their broader landscape can include sabkhas, playa-like depressions, gravel interdunes, dry lake beds, exposed rock, ephemeral channels, oasis margins, and vegetated dune toes.

The relationship between sand and surrounding terrain helps explain why desert landscapes look so different from one region to another. In the Sahara, dunes may accumulate beside rocky plateaus. In Iran, dune fields can meet salt basins. In Arabia, dunes may alternate with hard saline flats. In China, giant dunes can surround lakes.

This mixed landform context is also visible from satellites. Large-scale dune orientation, sand color, interdune spacing, drainage remnants, and surface boundaries often show sediment sources and dominant transport directions more clearly than ground-level observations alone.

Why Dunes Move or Remain Fixed

Dune mobility depends on the balance between wind energy, available loose sand, vegetation, moisture, and surface crusts.

Where dry loose sand is abundant and wind remains strong, dune crests and entire smaller dunes can migrate. Where vegetation establishes, moisture increases, or crusts bind the surface, movement slows.

Large dunes can be partly stable while smaller superimposed dunes remain active. A sand sea should therefore not be classified as simply “moving” or “fixed” without considering individual sectors and dune scales.

Natural and Managed Stabilization

Dune stabilization can occur naturally through vegetation growth, seasonal moisture, reduced sediment supply, or surface crust development. Human land management can also influence mobility.

Karapınar provides an example of vegetation and land management being used to limit wind erosion. Northern China contains many projects using shelterbelts, vegetation, sand barriers, and other techniques near roads, settlements, and agricultural land.

Stabilized dunes can become active again if vegetation cover declines or if changes in wind, sediment supply, or surface moisture expose loose sand.

Sources

• U.S. Geological Survey – Types of Dunes (crescentic, linear, star, dome, parabolic, compound and complex dune forms)
• U.S. Geological Survey – Eolian Processes (saltation, creep, slipfaces and dune migration)
• NASA Earth Observatory – Empty Quarter (Rub’ al Khali area and sand-sea geography)
• NASA Earth Observatory – Ar Rub’ al Khali Sand Sea (erg definition, linear dunes, star dunes and sabkhas)
• NASA Earth Observatory – Great Sand Sea (linear dune landscapes in the Sahara)
• UNESCO World Heritage Centre – El Pinacate and Gran Desierto de Altar (North America’s largest active dune system and only active erg)
• UNESCO World Heritage Centre – Badain Jaran Desert (mega-dunes, interdunal lakes, World Heritage area and dune height)
• Experience Oman – A’Sharqiyah Sands (official approximate area and landscape description)
• Geoscience Australia – Areas of Australian Deserts (Simpson and Great Sandy Desert areas)