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
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.
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 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.