Aeolian Landforms of Deserts
Geography › Rocks, Erosion and Landforms · Topic 5.9
Aeolian landforms are shaped by wind, especially in deserts, where there is little vegetation. Wind erodes by deflation and abrasion, creating deflation hollows, desert pavements, mushroom rocks and yardangs, and deposits sand as dunes such as barchans and seif dunes, and fine dust as loess. Water also acts in deserts, forming wadis, playas, pediments and inselbergs.
6 min read · UPSC Prelims · Geography · Rocks, Erosion and Landforms
At a Glance
- Wind erosion Deflation and abrasion
- Erosional forms Hollows, pavement, mushroom rock, yardang
- Depositional forms Dunes, loess
- Dune types Barchan, seif, transverse, star
- Water-made forms Wadi, playa, pediment, inselberg
- Exam link UPSC Prelims, Geography: Rocks, Erosion and Landforms
Where Does It Fit?
This is the last topic of the category on rocks, erosion and landforms. The previous topic described glacial landforms, and this one covers desert landforms. The next category begins with the atmosphere and the evolution of its composition. Previous topic: Glacial Landforms. Next topic: Evolution and Composition of the Atmosphere.
How Does Wind Shape Deserts?
In short: in deserts, wind lifts and carries sand and dust, and builds dunes and carves rocks.
Deserts are regions with very little rainfall, usually less than about 250 mm a year, sparse vegetation and a great range of temperature. Hot deserts lie mostly in the subtropical belts between about 15 and 30 degrees north and south, where descending dry air dominates, as in the Sahara, Arabian, Thar, Kalahari and Australian deserts, and are linked to the pressure belts described in Pressure Belts and Pressure Cells. Dry soil and bare ground leave particles exposed, so wind is a powerful agent. It acts through deflation, the lifting and removal of loose particles, which lowers the surface, and abrasion, the sandblasting of rock by wind-borne grains, as explained in Soil Erosion – Water and Wind Erosion. Though wind is the typical agent, desert landforms also result from rare but violent rains and flash floods, and so many desert landscapes are partly the work of water.
What Are the Erosional Aeolian Landforms?
| Landform | Description |
|---|---|
| Deflation hollow (blowout) | A shallow depression where wind has removed loose material; may reach the water table and form an oasis |
| Desert pavement (reg, serir) | A surface of closely packed pebbles left when the finer sand and dust has been blown away |
| Ventifact | A stone polished or faceted by wind-blown sand |
| Mushroom rock (pedestal rock, gara) | A rock with a narrow base and a wider top, eroded more at the base where the sand-laden wind is strongest |
| Yardang | A streamlined ridge of soft rock carved parallel to the direction of the prevailing wind |
| Zeugen | Table-like ridges of hard rock capping softer rock |
What Are the Depositional Aeolian Landforms?
Where the wind loses speed or meets an obstacle, it drops its load. Sand accumulates as dunes, and a large area of sand dunes is an erg or sand sea. Common dune types:
| Dune | Shape and setting |
|---|---|
| Barchan | Crescent-shaped, with the horns pointing downwind; forms where wind is steady in one direction and sand is limited; common in the Thar and the Sahara |
| Transverse dune | Long ridge at right angles to the wind; where sand supply is abundant |
| Seif (longitudinal) dune | Long, narrow ridge parallel to the wind; can be hundreds of km long, in the Sahara and Arabia |
| Parabolic dune | U-shaped, with the arms pointing upwind, held by vegetation |
| Star dune | Pyramid with several arms, where winds blow from many directions |
Wind also carries fine dust over long distances. Loess is a fine, yellowish, wind-blown silt deposited in thick layers, as in northern China, where the Loess Plateau was built by dust from the Gobi and Central Asian deserts, and in parts of the Punjab and Haryana plains. Loess forms fertile soils. The Thar desert of Rajasthan has barchans and many other dunes, as does the Great Indian Desert across Rajasthan, Gujarat, Punjab and Haryana, and the Cold Desert of Ladakh has dunes too, for example around Nubra Valley.
Which Landforms Are Made by Occasional Water in Deserts?
- Wadi (arroyo): a dry stream valley that carries water only after rain.
- Playa: a flat, dry lake bed with salt crust, where a temporary lake gathered; a salt playa is also called a salina. The Rann of Kachchh is a large salt marsh of this type.
- Alluvial fan and bajada: fans at the mountain foot may merge into a continuous sloping apron called a bajada.
- Pediment: a gently sloping rock surface at the base of a retreating mountain front.
- Inselberg: an isolated rocky hill rising abruptly from a plain; Uluru (Ayers Rock) in Australia is the famous example, and in India, isolated hills of the Peninsula and the Aravalli foreland are similar.
- Mesa and butte: flat-topped plateau remnants, and smaller ones, formed by erosion of layered rocks.
Why Does the Thar Desert Matter for India?
The Thar occupies about 200,000 sq km of Rajasthan and extends into Gujarat, Haryana and Punjab, with rainfall mostly under 250 mm in the west. It is the most densely populated desert in the world. The Aravalli range lies to its east, and the Indira Gandhi Canal brings Himalayan water to western Rajasthan, which has made farming possible in parts of the desert. Shelterbelts and stabilisation of dunes are used to fight encroaching sand, as discussed in Case Studies – Indira Gandhi Canal and Bharmaur Tribal Region. The monsoon winds do not bring much rain to the Thar, as in Mechanism of the Indian Monsoon. As an analytical point, desert landforms show how a landscape records both the dominant process and the rare event: the dunes show the wind of centuries, but the wadis show flash floods of a few hours.
Why Is This Topic Important?
- Dunes Types and shapes asked
- Thar Indian desert features
- Loess Fertile deposits
What Came Next?
The next category begins with the atmosphere. The first topic is Evolution and Composition of the Atmosphere.
Key People and Terms
- Deflation Removal of loose particles by wind
- Barchan Crescent-shaped dune
- Erg Sand sea
- Loess Wind-blown silt deposit
- Playa Dry desert lake bed
- Inselberg Isolated rocky hill
Exam Corner
Points to Remember
- Wind erodes by deflation and abrasion.
- Barchan horns point downwind.
- Seif dunes lie parallel to the wind.
- Loess is wind-blown silt.
- Thar is about 200,000 sq km.
Do Not Confuse With
- Barchan and seif dunes Crescent versus long ridge
- Deflation and abrasion Lifting versus sandblasting
- Wadi and playa Dry stream versus dry lake
Memory Hook
Wind lifts, wind blasts, wind builds: barchan crescent, seif ridge, loess dust.
Mains Angle
Questions ask for desert landforms and the Thar. These points add depth.
- Wind Erosion and deposition
- Water Flash floods shape deserts
- Thar Dunes and canal
A Question You May Face
An original practice question, not a past paper question.
“Explain the formation of the main erosional and depositional landforms in hot deserts.”
How to Answer
- Agents Wind and flash floods.
- Erosional Hollows and mushroom rocks.
- Depositional Dunes and loess.
- Example Thar desert.
GS Relevance
Frequently Asked Questions
What are aeolian landforms?
Aeolian landforms are those shaped by wind. Wind erosion makes deflation hollows, desert pavements, mushroom rocks and yardangs, and wind deposition builds sand dunes of various types and spreads fine dust as loess, mainly in deserts and dry regions.
What is a barchan?
A barchan is a crescent-shaped sand dune with its horns pointing downwind. It forms where the wind blows steadily from one direction over a hard surface with a limited supply of sand, and it can slowly move forward. Barchans are common in the Thar and the Sahara.
What is loess?
Loess is a fine, yellowish, wind-blown silt deposit that forms thick, fertile layers. The best-known loess deposit is the Loess Plateau of northern China, built up by dust from the deserts of Central Asia, and there are also loess areas in the plains of north India.
What are deflation and abrasion?
Deflation is the removal of loose, fine particles from a surface by wind, which lowers the ground and may form hollows. Abrasion is the wearing down of rock by sand grains carried by the wind, which polishes and shapes rocks like sandpaper.
Where is the Thar desert located?
The Thar desert, or the Great Indian Desert, lies mainly in western Rajasthan and extends into Gujarat, Haryana and Punjab, with part in Pakistan. It covers about 200,000 sq km in India, receives under 250 mm of rain in the west, and has many barchan dunes.
PYQ Practice — Statement Analysis
1 Barchan dunes are crescent-shaped with horns pointing downwind.
They form under steady one-directional wind.
2 Loess is a deposit of coarse sand.
It is fine wind-blown silt.
3 A playa is a dry desert lake bed.
It often has a salt crust.
4 Deflation is the sandblasting of rocks by wind-borne sand.
That is abrasion; deflation is the lifting of loose particles.
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