Erosional Landforms

Mushroom or Pedestal rocks:

Wind erosion takes place at the average height of 1 meter from the Earth’s surface.
While above height of average 2 meters, erosional process is again very low.
As a result middle portion of vertical rocks is eroded by high speed winds and after erosion rocks look like mushrooms.
In Sahara desert such land forms are known as ‘Gaur’ and in Germany these are known as ‘Pitzfelsen’.

Ventifacts:

Ventifacts are geomorphic features made of rocks that are abraded, pitted, etched, grooved, or polished by wind-driven sand or ice crystals.
They are most typically found in arid environments with little vegetation to interfere with these erosive processes.
If ancient ventifacts can be preserved without being moved or disturbed, they are excellent paleo-wind indicators as the grooves and striations cut into the rock are parallel with the wind direction.

Zeugen:

‘Zeugen’ is a word from German language which means ‘Like Table’.
When soft rocks covered by hard rocks are eroded by winds, hard rocks left behind looks like table and known as ‘Zeugen’.
Their length may vary from 1 meter to 30 meters. Along with winds, rainfall and weathering also help in formation of ‘Zeugen’.

Yardangs:

Winds blowing continuously in one direction result in the erosion of zeugen in one direction/side only.
Zeugens are eroded much from windward side and less from leeward side.
This process forms a very queer structure of these rocks.
The ratio of these structures (length and breadth) varies from 3:1 and 4:1 and average height is around 8 meters. In India such landforms are found in Jaisalmer (Rajasthan).

Stone Lattice:

At times rocks are formed by the combination of both soft and hard types of stones.
Soft rocks and soft parts of such formations get eroded by winds and only hard parts are left behind which make formations look like ‘net’. These are known as Stone Lattice.

Driekanter:

The direction of winds is never fixed and in the absence of vegetation in a desert, various rocks get eroded continuously in the direction of wind.
With such continuous and all directional erosion, rocks attain a triangular shape and these are known as Driekanter.

Window & Bridge:

Continuous erosion by high velocity winds forms holes in the rocks. Such holes are called Wind Windows.
Further, the combined action of deflation and abrasion makes the wind windows larger and wider which assumes an arch like shape with solid roof over them. Such land forms are called Wind Bridges.

Demoislle:

Some hard rocks are wrapped all round by soft rocks.
With the continuous wind erosion soft rocks get vanished leaving behind the hard rock, which looks like a pillar. This pillar formation is known as Dermoislle.

Lag Deposits:

Fast blowing wind carries lighter particles like sand, small pebbles and stones with it.
While heavier stones and other big particles lag behind.
These particles look like a layer of heavy stones and rubble. Such layers are very common in desert regions.
In Sahara desert such lag deposits are known as ‘Hamada’ in local language.

Deflation Basins:

Deflation is the removal of loose particles from the ground by the action of wind.
When deflation causes a shallow depression by persistent movements of wind, they are called as deflation hollows.
Found on the Southern High Plains of northwestern Texas and eastern New Mexico
A good example of these hollows is Qattara Depression in the south west of Alexandria, Egypt. This hollow is about 120 m below the sea level.

Oasis:

During deflation the upper layers of stones are eroded by high speed winds and rocks having water appear on the surface.
Because of this underground water oozes out (comes out) which is known as Oasis.
Any type of vegetation and human life is possible around oasis. These landforms are found in desert regions of Algeria, Libya and Thar in India.

Needles:

Complete to erosion of soft rocks by high speed winds allows steep gradient rocks stand uneroded and still. They look like needles and therefore known as rocky Needles.

Inselberg:

Wind erosion makes desert appear/look like plain but at some places some small mountains of solid rocks are found. These mountains are known as Inselbergs.
Aabu (Graynite Inselberg) and Sendra near Pali are the finest examples.

Pediplains:

When the high relief structures in deserts are reduced to low featureless plains by the activities of wind, they are called as Pediplains.
Selected Australian regions are considered as possible as examples of pediplains.