World Geography: Landforms of Wind Erosion in Desert

Rock pedestals / Mushroom rocks

• Formed by the sand blasting effect of winds against any projecting rock masses
• It wears down the softer layer leading to formation of irregular edges on alternate bands of softer & harder rocks.
• Grooves & hollows cut in the rock surfaces, carve them into grotesque looking pillar known as rock pedestals.
• Such rock pillars will be further eroded near their bases where friction is greatest.
• This process of undercutting produces rocks of mushroom shape called mushroom rocks.

Mushroom rocks

Zeugen

• Tabular masses which have a layer of soft rocks lying beneath a surface layer of more resistant rocks
• Difference in erosional effect of the wind on soft & resistant rock surfaces, carve them into weird looking ridge & furrow landscape
• Mechanical weathering initiates their formation by opening up joints of the surface rocks
• Wind abrasion further eats into underlying softer layer so that deep furrows are developed

• The hard rocks then stand above the the furrows as ridges or Zeugen
• Zeugen may stand 10 to 100 feet above the sunken furrows
• Continuous abrasion by winds gradually lowers the Zeugen & widens the furrow

Yardangs

• Yardangs looks quite similar to Zeugen but instead of lying in horizontal starta upon one another, the hard & soft rocks of Yardangs are vertical bands
• Rocks are aligned in the direction of prevailing winds.
• Winds abrasion excavates the bands of softer rocks into long, narrow corridors, separating the steep sided overhanding ridges of hard rocks called Yardangs.

Mesas & Buttes

• Mesa is a flat, table like land mass with a very resistant horizontal top layer & very steep sides, may be formed in canyon region.
• The hard stratum on the surface resist denudation by both wind & water thus protects the underlying layer of rocks from being eroded.
• Continuous denudation through ages may reduce Mesas in area so that they become isolated flat topped hills called Buttes.
• Many of which are separated by deep gorges & canyons.

Isenberg (Island Mountain)

• They are basically isolated residual hills rising abruptly from the ground level
• Characterized by very steep slopes & rather rounded tops
• They are often composed of granite or gneiss
• Are probably relics of an original plateau, which has been almost entirely eroded away

Ventifacts & Dreikanter

• Ventifacts are generally pebbles faceted & edged by sand blasting
• Rock fragments weathered from mountains

• Are shaped & polished thoroughly by wind abrasion
• Smoothened on windward side

• If wind direction changes another facet is developed.
• Among the ventifacts, those with the three wind faceted surfaces are known as Dreikanter.

Deflation Hollows

• Wind lowers the ground by blowing away the unconsolidated material & hence forms small depressions.
• Similarly, minor faulting can also initiate depressions which along with the eddying action of oncoming winds will wear off the weaker rocks until water table is reached.

• Water then seeps out forming oasis or swamps in deflation hollows or depressions.
• Large areas in western USA, was stripped of their natural vegetation & was completely deflated by strong winds, that moved materials as dust storms & creating what is now known as Great dust bowl.