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.
- 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 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.
- 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.