Winds are also capable of degrading the land, but their erosional and transportation ability is inferior to that of the water. Winds, like other forms of denudation, also cause erosion and friction. Winds transport rock and soil particles from one location to another. Wind creates a few erosional and depositional features such as pediplains, playas, deflation hollows, barchan, seif, etc. which are discussed in detail in this article.

Actions of Wind

• The wind is a primary geomorphic agent in hot deserts.
• Winds blow faster in hot deserts, causing erosion and depositional activities in the desert.
• Aeolian landforms are landforms that are formed by the wind's erosional and depositional actions.
• This phenomenon isn't unique to Earth; it's been noticed and investigated on other planets as well, including Mars.
• An erg (also called a sand sea, dune sea, or sand sheet if there are no dunes) is a large, flat region of desert covered with wind-blown sand with little or no vegetation.
• It is described as a desert area with aeolian or wind-blown sand covering more than 125 square kilometers and sand covering more than 20% of the surface.

Stages of Erosional Process by Wind

Deflation

• This stage includes picking up and blowing away loose items like dirt and rock fragments from the ground by high-speed winds.
• Blowing capacity is mostly determined by the size of the material being lifted from the ground.
• Finer dust and sands can be transported miles from their source and deposited far outside the desert borders.
• Deflation causes the land surface to sink, forming enormous depressions known as deflation hollows.
• Hollows are sometimes generated as a result of this process, which is typically minor in size but can range in diameter from 1 to 15 kilometers.

Abrasion

• High-speed winds carry soil and rock particles, as well as small rocks and other debris.
• These are also known as wind tools.
• The wind sandblasts rock surfaces by hurling sand particles on them.
• This debris acts like sandpaper, causing erosion and friction on adjacent rocks, a process called abrasion.
• Rock surfaces are scratched, polished, and worn away as a result of this.
• The amount of material that the wind can carry is greatest near the base of the rocks, hence abrasion is most effective there.
• This helps to explain why telegraphic poles in the desert are covered with metal for a foot or two above the ground.

Attrition

• Sand particles carried by the wind begin a friction process within themselves, reducing their size. This is referred to as attrition.
• High-speed winds speed up the erosional process.
• Hard rocks, on the other hand, take a long time to erode, whereas soft rocks do so quickly.
• Small particles can travel very long distances, whereas large pebbles and stones (with a radius of 5 to 8 centimeters) can only travel a short distance.

Erosional Landforms Due to Wind

Pediments

• A pediment is a gently sloping erosion surface or low-relief plain at the base of a receding mountain front in an arid or semiarid region.
• A pediment is often covered by a thin, discontinuous veneer of soil and alluvium produced from upland areas, which is underlain by bedrock.

Pediplains

• Pediplains are formed when high relief features in deserts are lowered to low featureless plains due to wind activity.
• The convergence of pediments forms a pediplain, which is a large flat landscape.
• Pediplanation is the term for the process by which pediplains form.

Deflation Hollows

• The removal of loose particles from the ground by the action of the wind is known as deflation.
• Winds can cause minor depressions in the ground by blowing away unconsolidated materials.
• Minor faulting can also generate depressions, and oncoming winds can erode the weaker rocks until they reach the water table.
• In the deflation hollows or depressions, water seeps out, generating oases or wetlands.
• Large sections of the western United States, which had been stripped of their natural vegetation for farming, were utterly deflated when strong winds carried materials as dust storms, laying waste crops and causing the Great Dust Bowl.

Playas

• A playa (also known as a pan, flat, or dry lake) is a depression with a flat floor found in interior desert basins.
• They are found near the beaches in dry and semi-arid locations.
• Playas are occasionally covered by water that slowly filters into the groundwater system or evaporates into the atmosphere, causing salt, sand, and mud to accumulate along the bottom and around the margins of the depression.

Mushroom Rocks

• A mushroom rock, also known as a rock pedestal, pedestal rock, or mushroom table, is a naturally formed rock that resembles a mushroom in shape.
• These rocks can be deformed in a variety of ways, including erosion and weathering, glacial action, or a sudden disturbance.
• These geomorphic landforms are most common in dry areas with little vegetation to obstruct aeolian particle movement, frequent high winds, and a steady but not excessive supply of sand.
• Winds convey a greater volume of sand and rock particles near the ground in deserts, causing more bottom erosion in overlying rocks than top erosion.

Depositional Landforms of Wind

Sand Dunes

• Sand dune formation is best in dry, hot deserts.
• Sand dune forms include Barchans, Seifs, and others, depending on the shape of the dune.
• They might be active or live dunes that are constantly moving, or they can be inert permanent dunes that are anchored in vegetation.

Barchan

• A crescent-shaped dune is known as a barchan or barkhan dune.
• Barchans face the wind, appear convex, and are primarily formed by the wind from one direction.
• They are arc-shaped, significantly asymmetrical in cross-section, with a gradual slope facing the wind sand ridge, and made out of well-sorted sand.
• They are found in sandy deserts all over the world.
• Two "horns" face downwind on this type of dune, with the steeper slope known as the slip face facing away from the wind.

Seif

• A seif is a long, narrow sand dune or a chain of dunes that is generally directed parallel to the prevailing wind or in a direction formed by two or more winds blowing at sharp angles to one another.
• The dune crest is made up of a sequence of peaks and gaps, and the steep, or slip.
• The majority of seif dunes are found in the open desert, resting on a coarse sand sheet.
• In Libya and Southern Iran, seifs are very common.
• Crosswinds cause them to grow in height and width, whereas winds parallel to their axis cause them to grow in length.

Loess

• Fine dust blown beyond the desert's boundaries is deposited as loess on surrounding fields.
• It's a yellow, friable substance that's usually quite fertile.
• Loess is a fine loam that is high in lime, very cohesive, and porous.
• Water rapidly sinks into the surface, ensuring that it is always dry.
• Streams have cut deep valleys through the thick mantle of soft loess and badland topography may develop.
• It is so soft that roads constructed through a loess region soon sink and their walls rise steeply.
• The most extensive deposit of loess is found in northwest China in the loess plateau of the Hwang-Ho basin.

Parabolic Dunes

• Parabolic dunes are U-shaped sand mounds with convex noses and prolonged arms.
• These dunes are also known as U-shaped, blowout, or hairpin dunes and can be seen in coastal deserts.
• Their crests, unlike crescentic dunes, point windward.
• Since the extended arms of parabolic dunes have been fixed by vegetation, they follow rather than lead, although the majority of the sand in the dune migrates forward.
• The trailing arm of the world's longest known parabolic dune is 12 kilometres long.

Transverse Dunes

• Long sand dunes with a wavy ridge running along their length are known as transverse dunes.
• These sand dunes are arranged in parallel or side-by-side rows.
• Winds carrying a lot of sand create them.
• The ridges found here are perpendicular to the wind's direction.

Longitudinal Dunes

• Longitudinal dunes extend parallel to the direction of the prevailing wind, forming parallel ridges of dunes.
• Longitudinal dunes can emerge when sand supply increases to the point where barchans (which require little sand) can change into longitudinal dunes by elongating one of its limbs.

Conclusion

As an erosional agent, the wind is more effective in arid regions than humid regions because, in arid regions, there is little moisture and vegetation to bind the loose material. The wind’s action creates a number of interesting erosional and depositional features in the deserts. Wind erosion is carried out in desert areas in mainly three ways: Deflation, Abrasion, and Attrition.

FAQs

MCQs

1. Which of the following is NOT a result of wind erosion?

A) Ventifacts
B) Sand dunes
C) River valleys
D) Deflation hollows

2. Wind erosion is most prominent in which of the following regions?

A) Tropical forests
B) Coastal regions with dense vegetation
C) Deserts and arid regions
D) Wetlands

3. Which of the following features is primarily formed by the deposition of wind-blown sand?

A) Loess
B) River delta
C) Floodplain
D) Sand dunes

4. The term "deflation" in geomorphology refers to:

A) The movement of water across a surface
B) The removal of material by wind
C) The creation of riverbeds
D) The accumulation of sand in deserts

5. Which of the following is most likely to cause the formation of ventifacts?

A) Wind erosion
B) Water erosion
C) Glacial movement
D) Earthquakes

GS Mains Questions and Model Answers

Q1: Discuss the geomorphic processes of wind and their impact on desert landscapes.

Answer: Wind plays a significant role in shaping desert landscapes through erosion, transportation, and deposition. Wind erosion in deserts results in the removal of fine particles, leading to the creation of deflation hollows and the polishing of rocks into ventifacts. The transportation of sand across large distances leads to the formation of sand dunes. These dunes vary in shape and size depending on wind direction and intensity. Wind also deposits fine particles, forming loess, a fertile soil in certain areas. The interaction between wind and the desert environment creates dynamic and constantly changing landscapes, making them vulnerable to further erosion if not protected by vegetation.

Q2: Explain the differences between wind and water as geomorphic agents. How do they each contribute to landscape formation?

Answer: Wind and water are both powerful geomorphic agents but differ in their processes and effects. Water is denser and has greater erosive power, capable of moving large rocks and forming valleys, rivers, and cliffs. It typically shapes landscapes in wetter regions. In contrast, wind is more effective in dry, arid regions where it primarily moves finer particles like sand and dust. Wind erosion leads to the formation of dunes, deflation hollows, and ventifacts, whereas water creates river valleys, deltas, and floodplains. While water erosion is more widespread and aggressive, wind erosion, though less intense, is significant in shaping deserts and coastal regions with minimal vegetation.

Q3: Discuss the role of wind in the formation of desert features and their implications for human settlements.

Answer: Wind plays a crucial role in shaping desert features like sand dunes, deflation hollows, and ventifacts. These features affect human settlements by influencing agriculture, water availability, and infrastructure development. For instance, sand dunes can block roads or bury infrastructure, making them a challenge for settlement in desert areas. Deflation hollows can lead to water scarcity by reducing surface water retention. However, areas with stabilized dunes may be suitable for agriculture, as the accumulation of loess creates fertile soil. Understanding wind-driven geomorphic processes is essential for managing human activities in desert environments and ensuring sustainable development.

Previous Year Questions on Wind as a Geomorphic Agent

1. UPSC CSE Prelims 2020:

Question: Wind erosion is primarily responsible for the formation of:

A) River valleys
B) Sand dunes
C) Glacial valleys
D) Coastal cliffs

Answer: (B)

Explanation: Wind erosion is primarily responsible for the formation of sand dunes, especially in deserts and coastal regions. Wind erodes, transports, and deposits sand, which accumulates to form dunes.

2. UPSC CSE Mains 2017 (GS Paper 1):

Question: Explain the geomorphic effects of wind in arid and semi-arid regions.

Answer: Wind in arid and semi-arid regions is a powerful geomorphic agent that leads to the erosion, transportation, and deposition of material. Erosion results in the creation of ventifacts and deflation hollows, while transportation moves sand and dust across vast distances. The deposition of sand leads to the formation of dunes. These wind-formed features significantly alter the landscape over time, shaping desert ecosystems and influencing human activities. Wind erosion also contributes to the formation of fertile loess deposits in some areas, benefiting agriculture.