An essay: “Wind processes are dominant in forming landforms in hot arid deserts.” With the use of landforms that you have studied, evaluate to what ext ent this statement is true. [20] 18 marks were achieved out of 20 for this essay.
“Wind processes are dominant in forming landforms in hot arid deserts.” With the use
of landforms that you have studied, evaluate to what extent this statement is true. [20]
(18)
Hot arid deserts have some of the most jaw dropping landforms in the world today. A hot arid
area is characterised by less than 250 mm of precipitation a year and falls in between -40
and -56 on Meigs’ classification of aridity. They also typically occur between 20° and 30°
North and South of the equator. This essay will analyse if aeolian processes can take most
of the credit for these stunning landforms.
Firstly, it will be discussed whether wind erosion is the main reason for desert landforms.
The wind erosion role in desert landforms was down played until recently. Wind erosion
works mainly through carrying sand through surface creep, saltation and suspension which
causes erosion through abrasion, effective upto about 1-1.5 m high. Yardangs, zeugen,
gours, ventifacts, and desert pavement are all believed to have come from aeolian
processes. Ventifacts are sandblasted rocks situated in a multimodal wind regime. The rock
is flattened and smoothed down by sand hitting it, creating facets and ridges. Yardangs’
troughs are almost completely reliant on wind erosion to be created. Finally aeolian
processes have created the most famous desert landform of all, dunes! These would not
exist if it were not for wind congregating sand. It is evident that aeolian processes are
responsible for a vast number of desert landforms.
However, present day fluvial processes are also to be considered. Present day fluvial
processes have been said to form chottes and alluvial fans, sometimes also gullies and
inselbergs. Alluvial fans are formed when a river exits the confines of a wadi spreading into
sheetwash losing competence and capacity and depositing its load of sand and silt. Yet,
even though they may form a number of landforms, the infrequency at which fluvial
processes occur combined with the small scale suggests it is not such a dominant process in
a current interpluvial period.
There is, however, the Pleistocene Ice Age, which can perhaps aid fluvial processes in being
considered the most dominant. This pluvial period is responsible for arroyos, canyons,
mesas, buttes, pediments, inselbergs and gullies. During the Pleistocene, fluvial processes
created mesas, through streams heavily dissecting the land, leaving a single part of the
plateau separated from the rest. The heavy dissection also created arroyos and canyons.
Due to the high levels of precipitation, hydrolysis was also common, breaking up granite
underground, by reacting with the feldspar to create china clay. This then left large blocks
sitting on top of each other as the soil was removed by streams of rain and also sometimes
wind. This created inselbergs. Here we see that fluvial processes during the Pleistocene
played a key role. So, while no single weathering or erosional process acts alone, it can be
understood that fluvial processes in the Pleistocene have allowed the aeolian processes to
be more dominant now as it created mesas, to be turned into buttes, zeugens to be turned
into hoodoos and rock pedestals among many other landforms.
In conclusion, the dominance of the fluvial processes in the Pleistocene has paved the way,
through the landforms it created, for aeolian processes to be the most dominant now. This is
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