Erosional landforms of wind :Deflation hollows and caves Upsc

The wind is one of the two dominant agents in hot deserts. The desert floors get heated up too much and too quickly because of are dry and barren.

The heated floors heat up the air directly above them and result in upward movements in the hot lighter air with turbulence, and any obstructions in its path set up eddies, whirlwinds, updrafts, and downdrafts.

Winds also move along the desert floors with great speed and the obstructions in their path create turbulence. Of course, there are storm winds that are very destructive.

Winds cause deflation, abrasion, and impact. Deflation includes lifting and removal of dust and smaller particles from the surface of rocks.

In the transportation process sand and silt act as effective tools to abrade the land surface. The impact is simply the sheer force of momentum which occurs when sand is blown into or against a rock surface. It is similar to sandblasting operation.

The wind action creates a number of interesting erosional and depositional features in the deserts.

In fact, many features of deserts owe their formation to mass wasting and running water as sheet floods. Though rain is scarce in deserts, it comes down torrentially in a short period of time.

The desert rocks devoid of vegetation, exposed to mechanical and chemical weathering processes due to drastic diurnal temperature changes, decay faster and the torrential rains help in removing the weathered materials easily.

That means the weathered debris in deserts is moved by not only wind but also by rain/sheet wash.

The wind moves fine materials and general mass erosion is accomplished mainly through sheet floods or sheet wash. Stream channels in desert areas are broad, smooth, and indefinite and flow for a brief time after rains.

Erosional landforms of wind

Pediments and Pediplains Landscape evolution in deserts are primarily concerned with the formation and extension of pediments. Gently inclined rocky floors close to the mountains at their foot with or without a thin cover of debris are called pediments.

Such rocky floors form through the erosion of the mountain front through a combination of lateral erosion by streams and sheet flooding.

Erosion starts along the steep margins of the landmass or the steep sides of the tectonically controlled steep incision feature over the landmass.

Once, pediments are formed with a steep wash slope followed by a cliff or free face above it, the steep wash slope and free face retreat backward.

This method of erosion is termed a parallel retreat of slopes through backwashing. So, through parallel retreat of slopes, the pediments extend backward at the expense of the mountain front, and gradually, the mountain gets reduced leaving an inselberg which is a remnant of the mountain.

That’s how the high relief in desert areas is reduced to low featureless plains called pediplains.


Plains are by far the most prominent landforms in the deserts. In basins with mountains and hills around and along, the drainage is towards the centre of the basin, and due to gradual deposition of sediment from basin margins, a nearly level plain forms at the centre of the basin.

In times of sufficient water, this plain is covered up by a shallow water body. Such types of shallow lakes are called playas where water is retained only for a short duration due to evaporation and quite often the playas contain good deposition of salts.

The playa plain covered up by salts is called alkali flats.

Deflation Hollows and Caves Weathered mantle from over the rocks or bare soil, gets blown out by the persistent movement of wind currents in one direction.

This process may create shallow depressions called deflation hollows. Deflation also creates numerous small pits or cavities over rock surfaces.

The rock faces suffer impact and abrasion of wind-borne sand and the first shallow depressions called blowouts are created, and some of the blowouts become deeper and wider fit to be called caves.

Mushroom, Table, and Pedestal Rock Many rock-outcrops in the deserts easily susceptible to wind deflation and abrasion are worn out quickly leaving some remnants of resistant rocks polished beautifully in the shape of mushroom with a slender stalk and a broad and rounded pear-shaped cap above.

Sometimes, the top surface is broad like a tabletop and quite often, the remnants stand out like pedestals.

* * All the Notes in this blog, are referred from Tamil Nadu State Board Books and Samacheer Kalvi Books. Kindly check with the original Tamil Nadu state board books and Ncert Books.