Wind can shape landscapes in surprisingly organised ways. One of the clearest examples is the yardang: an elongated, streamlined ridge carved mainly by wind erosion into relatively weak or fine-grained material.
Yardangs occur on Earth and Mars. Their shape can preserve clues about the direction of persistent winds, the resistance of the underlying material and the history of erosion over long periods of time.
The topic has fresh relevance because NASA released a new Curiosity panorama on 6 October 2026 showing distant wind-carved Martian cliffs. The rover is travelling towards a region known as the Yardang Unit on Mount Sharp, where scientists hope to investigate how this unusual layer formed.
What is a yardang?
A yardang is a streamlined landform produced by erosion rather than deposition. Instead of being built up from loose sediment, as a dune is, a yardang is what remains after wind removes less-resistant material from a pre-existing surface.
NASA describes a yardang as an elongated ridge created by wind erosion. On Earth, U.S. Geological Survey research describes yardangs as streamlined, wind-eroded hills common in deserts.
The exact size and appearance vary. Some yardangs are low ridges; others can become large cliffs or long, parallel landforms. Their shapes often resemble an inverted boat hull or teardrop, with their long axes aligned with the direction of persistent erosive winds.
How do yardangs form?
Yardang formation is not one single process. Several wind-driven processes work together over time.
1. Weak or fine-grained material is exposed
The starting material may be soft rock, compacted sediment, volcanic ash-rich deposits or another surface that contains layers with different resistance to erosion.
2. Wind transports sand and dust
Wind itself exerts force on the surface, but wind-blown particles make erosion much more effective. Sand grains can strike exposed surfaces repeatedly.
3. Abrasion wears the surface down
Abrasion is the mechanical wearing of a surface by particles carried by wind. It is sometimes compared with sandblasting.
4. Deflation removes loose material
Deflation is the removal of loose, fine-grained particles by wind. As material is removed, shallow depressions and grooves can deepen.
5. Less-resistant material disappears faster
If some layers or patches are softer than others, they erode more quickly. More resistant material is left standing as ridges.
6. The ridges become streamlined
Continued airflow, abrasion and deflation can gradually shape the remaining ridges into elongated forms aligned with the dominant erosive wind.
Why does the shape of a yardang matter?
The streamlined form is not just visually distinctive. It can contain environmental information.
USGS wind-tunnel and field studies of yardangs at Rogers Lake, California, found that abrasion is especially important around the windward end, while deflation and airflow around the sides and downstream parts also contribute to the final form.
This means the long axis of a yardang can sometimes be used as a clue to the prevailing direction of erosion over time. Planetary scientists can compare many ridges across a landscape to infer regional wind patterns.
That interpretation must be cautious: the alignment records the dominant erosion responsible for shaping the landform, not necessarily the exact direction of the wind at the moment an image was taken.
What is Curiosity seeing on Mars?
NASA's Curiosity rover is climbing Mount Sharp, the approximately 5-kilometre-high mountain inside Gale Crater. Mount Sharp contains a sequence of rock layers that preserve different chapters of Mars' environmental history.
The rover is heading towards the Yardang Unit, a distinctive layer in the upper foothills. NASA notes that its colour, texture and tilted layers look different from lower parts of the mountain.
On 6 October 2026, NASA released a new panorama captured by Curiosity's Mastcam on 11 August 2026. The image shows distant wind-carved crags illuminated by morning sunlight. Mission scientists describe the view as their most detailed look yet at the yardangs from the rover's current position.
The origin of the layer itself is not yet settled. NASA has discussed the possibility that some of the material may have originated as volcanic ash, but this remains an idea to be tested rather than an established conclusion.
Why does Mars have so many wind-shaped features?
Mars has a thin atmosphere, but wind is still an active geological agent. NASA observations show that Martian winds can move sand, form ripples and dunes, transport dust and carve exposed surfaces.
Several conditions can favour yardang formation and preservation on Mars:
- large areas of exposed sediment and rock;
- abundant fine-grained or relatively weak deposits in some regions;
- very little vegetation to protect the surface;
- long periods over which erosion can operate; and
- broad, dry landscapes where wind can interact repeatedly with the same surfaces.
This does not mean that every Martian ridge is a yardang. Scientists examine shape, orientation, surrounding geology and other evidence before classifying a landform.
Yardang versus sand dune: what is the difference?
The distinction is fundamental.
A sand dune is mainly a depositional landform. Wind transports loose sand and deposits it where airflow and available sediment allow the grains to accumulate. Dunes can migrate as sand is continually moved.
A yardang is mainly an erosional landform. Wind removes material from an existing surface, leaving streamlined remnants behind.
A landscape can contain both yardangs and dunes. NASA's Mars Reconnaissance Orbiter has imaged areas where wind has carved yardangs while also depositing sand and forming ripples in nearby channels.
What can yardangs tell planetary scientists?
Yardangs can provide several kinds of evidence.
Past wind direction
Groups of similarly aligned yardangs can reveal the dominant direction of the winds that did most of the erosion.
Material resistance
Where softer layers disappear while harder layers remain, scientists can infer differences in the mechanical strength or composition of the surface materials.
Depositional history
The material being eroded had to be deposited or formed before the yardang was carved. Studying the layers can therefore help scientists reconstruct what existed before erosion began.
Climate and environmental change
On Earth, USGS research at Mesquite Lake Playa in the Mojave Desert shows that yardang formation and erosion can respond to changing wind, sediment and climatic conditions. Similar reasoning helps researchers use Martian landforms as evidence of environmental change, although Earth and Mars have very different climates.
Do yardangs last forever?
No. Yardangs are products of erosion, and erosion continues after they form.
USGS measurements in the Mojave Desert have documented continuing erosion of yardang surfaces through abrasion, deflation, loss of surface crusts and small collapses from their sides. Over sufficiently long periods, a yardang can shrink, break down or disappear.
This is useful scientifically because it reminds us that a yardang is not a fixed object. It represents one stage in the continuing evolution of a landscape.
Common misconceptions about yardangs
“Mars' atmosphere is too thin for wind to reshape the surface.”
False. Martian winds move dust and sand and can contribute to erosion, even though the atmosphere is much thinner than Earth's.
“A yardang is just another kind of dune.”
No. Dunes are primarily deposited from loose sediment; yardangs are carved from pre-existing material.
“The direction of a yardang tells us exactly which way the wind is blowing today.”
Not necessarily. Its orientation reflects the dominant erosion that shaped it over time.
“All streamlined ridges on Mars are yardangs.”
No. Shape alone is not enough; geological context matters.
“Once a yardang forms, it is permanent.”
No. Continued erosion can eventually modify or destroy it.
A simple way to read a yardang landscape
When looking at a rover or orbital image, start with four questions:
- Are the ridges elongated and similarly aligned?
- Do grooves or troughs separate more resistant ridges?
- Is there evidence that loose material has been removed rather than deposited?
- Does the surrounding geology support prolonged wind erosion?
No single clue proves the interpretation, but several clues together can make the case much stronger.
Key takeaways
- A yardang is a streamlined erosional ridge carved mainly by persistent wind.
- Abrasion and deflation help remove weaker material while more resistant material remains.
- Yardang orientation can preserve evidence of long-term prevailing erosive winds.
- Yardangs differ from dunes because dunes are mainly depositional, while yardangs are erosional remnants.
- Curiosity is approaching the Yardang Unit on Mount Sharp, where scientists hope to investigate how the unusual Martian layer formed.
- Earth yardangs provide useful analogues for understanding wind erosion on Mars.
Frequently asked questions
Are yardangs found only on Mars?
No. They occur on Earth in dry environments and have also been identified on Mars. Earth examples help scientists understand the processes that can create similar forms elsewhere.
Can yardangs reveal ancient winds?
They can provide evidence of the dominant erosive wind direction over long periods, especially when many ridges share a consistent alignment.
Are yardangs made of sand?
Not necessarily. They can be carved into weak rock, compacted sediment or other erodible materials. A dune, by contrast, is built mainly from loose deposited sand.
Why is Curiosity interested in the Yardang Unit?
The layer differs from lower parts of Mount Sharp in colour, texture and tilt, and its origin is uncertain. Reaching it gives the rover a chance to examine material that may preserve another chapter of Mars' environmental history.
Does wind erosion happen quickly?
The rate depends on material, wind, sediment supply and environment. Some Earth yardangs can measurably erode over years or decades, while large planetary landforms may reflect much longer histories.
Authoritative references
- NASA / Jet Propulsion Laboratory, NASA's Curiosity Rover Catches Stunning Martian Dawn, 6 October 2026.
- NASA Science, Curiosity Views the Yardang Unit, 18 November 2024.
- U.S. Geological Survey, Ward & Greeley, Evolution of the Yardangs at Rogers Lake, California.
- U.S. Geological Survey, Whitney et al., Aeolian responses to climate variability during the past century on Mesquite Lake Playa, Mojave Desert.
- U.S. Geological Survey, Eolian Processes.
