How weathering and erosion shape landscapes
Introduction
Weathering and erosion are two independent but nonexclusive processes that slowly work together to carve, rub and buff the earth’s surface into an ever changing art work. Weathering defines the process through which rocks, soil as well as minerals breakdown after coming into contact with the atmosphere, water and natural organisms. Weathering, which may either be mechanical, chemical or even biological, takes place in situ and hence should not be mystified with erosion (Page, 2016). On the other hand, erosion defines the process by which soil, rocks, as well as minerals are moved by various agents including flowing water, wind, rain ice and snow and placed in different locations. The two processes work interchangeably to reveal awesome sights of nature, which range from falling boulders on high mountains to beautiful sandstone arches in the desert and refined cliffs propped against the sea (Lech, 2013). This paper explores how weathering as well as erosion shape landscapes in the desert.
How weathering as well as erosion shape landscapes in deserts
Weathering and erosion have played an important role in shaping the vast number of landforms that we see today. Physical weathering is the most apparent type of weathering that play an important role in shaping landscapes in the desert. According to Page, (2016), high temperatures during the day in the desert cause rocks to expand while low temperatures at night cause them to contract. This exerts a lot of pressure on the rocks thereby causing them to fracture. Physical weathering in the desert may also take place when salt is deposited in the cracks that form between rocks. Constant salt deposits lead to formation of salt crystals that may eventually force the rocks to break apart (Lech, 2013). Chemical as well as biotic weathering may on rare occasions be responsible for the breakdown of rocks in the desert. This is because there is less water and biotic organisms such as animals and plants in the desert although dew and barrowing animals can make little impact (Page, 2016).
Owing to the fact that deserts have very little vegetation, they tend to be susceptible to wind erosion. The wind blows against the already fractured rocks while blasting sand grains against rock overhangs. This may wear the rocks down thereby making various land reforms through the abrasion process. As explained by Lech (2013), the wind can carry all the sand while leaving behind heavy rocks in the desert. This can eventually create a rocky landscape known as a gibber desert that is characteristic closely packed angular or rounded portions of fragmented rocks. Over time, the exposed portions of fragmented rocks may transform into attractive alluvial fans. The Gibber Plains that cover a vast area of Central Australia are suitable examples of gibber deserts that form as a result of physical weathering and the subsequent wind erosion. The wind can equally blow away all the sand deposits to create a smooth flat plain that surrounds a secluded hilly region (Page, 2016). The hilly region may comprise of small mountains popularly known as inselbergs that abruptly rise from a virtually level of slightly sloping plain. According to Lech, (2013), inselbergs usually form from a moderately hard rock such as the granite or from sedimentary rocks such as sandstone. Suitable examples of inselbergs can be found in western part of Brazil, central Australia and central Africa.
Wind erosion in the desert may cause sand sediments to be carried from one location to the other. The sediments may be deposited at a particular location for a long period of time to form sedimentary rocks that usually occur in layers. Weathering activities may on the other hand cause the sedimentary rocks to fracture. While the top layer of the fractured sedimentary rocks may be hard and resistant to erosion, abrasion by wind mainly occurs on the sides of hilly rocks thereby causing them to smoothen (Lech, 2013). This leads to the formation of table-like features known buttes or mesas, which have steep smooth sides and flats tops. Common examples of buttes as well as mesas are found in the Australian Basin and Western Australia. While mesas are usually larger than buttes, their distinctive attribute is that mesas have an appearance of elevated pieces of land that have flat tops while buttes look are like small hills with vertical sides and moderately flat tops ((Page, 2016)).
In addition to abrasion, deflation can also play an important role in removing loose sediments that may have formed as a result of physical weathering in the desert. According to Page, (2016), the removal of loose sediments as a result of wind erosion can lower the level of the land surface in the desert to form depressions known blowouts. Blowouts are similar to craters and are mainly found in Texas. The removal of loose sediments through wind as well as sheet erosion can leave large stones concentrated at the base of the surface in the desert. The stones can in return restrict the underlying smaller sediments thereby preventing further erosion. This can lead to the formation of desert pavements that are popularly known as cobblestone pavements. The Gibber desert pavement in Central Australia is a suitable example (Lech, 2013).
Conclusion
Weathering as well erosion are critical natural processes that contribute to the formation of vast landscapes found in the desert. Physical weathering is basically responsible for the fracturing of rocks in the desert, which releases loose sediments that are usually blown away by the wind while leaving large rocks to be chiseled, smoothened and curved by the wind. Wind erosion usually occurs through abrasion and deflation processes, which allows for the formation of various landscapes. Such landscapes include inselbergs, giber deserts, blowouts, buttes and mesas.
References
Lech, M. (2013). Weathering, Erosion, Landforms and Regolith. Australia: Geoscience Australia.
Page, K. (2016). Is it Erosion or Weathering? Science and Children, 53(7):189-267.