• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Wind is an important agent of transport and deposition. It's effectiveness as an eroder remains questionable. Discuss.

Extracts from this document...

Introduction

Wind is an important agent of transport and deposition. It's effectiveness as an eroder remains questionable. Discuss. A desert can be defined as any region that receives less than 25cm of rain per year where evapo-transpiration equals or exceeds precipitation or in other terms where there is a permanent moisture deficit. Arid areas cover one third of the earth's land surface and there is an enormous amount of variety within in them. Most of these deserts lie in the tropical and subtropical belts between 20o and 30o north and south of the Equator. Wind, as in other physical systems, can erode, transport and deposit but as stated its role as an eroder remains open to discussion. Transport in deserts is carried out in three processes, being suspension, through the air less than 25 metres above ground level; saltation, where grains bounce a few cm above the ground; and surface creep. In suspension very fine material is picked up by the wind, raised to considerable heights and carried great distances. The finer materials are taken away leaving behind a lag deposit. Transport is effective and important here in that in 1km of air, 900 tonnes of sand can be entrained. ...read more.

Middle

Deposition of transported sand grains is also an important process in deserts and wind plays the major role here. Deposition comes in three main forms, ripples, dunes and draa where dunes will be concentrated on. Dunes develop when sand grains, moved by saltation and surface creep, are deposited. The first here is the Barchan Dune, a crescent shaped dune up to 30m high, aligned importantly 90o to the wind. They start life as a mound of sand and windward grains are moved by saltation over the apex to accumulate on the lee side. Horns develop on either side as these grains move faster than the heavier middle: Secondly Seif dunes, much larger than Barchan dunes are created by a combination of deposition and transportation. There are two theories as to how they are created. On one hand they are though to be simply an extension of Barchan dunes where one horn elongates and migrates (Bagnold). On the other hand wind is though to act in a 'vortex flow' that whips up the sand: But in any case the winds are steady and persistent with slight diurnal changes in direction. Lastly obstacle dunes arise where transportation is interrupted by some impediment. ...read more.

Conclusion

The desert can often be covered by protective duricrusts (particles cemented together). Records also show that strong long-term winds do not occur and abrasion only occurs 1.5m above the land surface. Some support, though is given for winds effectiveness as an eroder with satellite photos showing hard bedrock features from Iran, Peru and the Sahara have the same alignment as the prevailing wind. It seems that in extremely dry deserts such as the Namib that wind is a major process and the formation of isolated mountains (Inselbergs) is attributed to wind planation. This is termed as the phase of 'extravagant aeolation'. Whereas in the 'wetter' deserts of North America, wind is less effective, as mentioned above, where wind eroded features are only minor, and wind erosion is shown to have a limited height range. In conclusion it is safe to say that wind is an important agent of deposition and transportation and still contributes to erosion. Its role as an eroder is not as effective as the other two processes, as other factors contribute creating equifinality of form, but it is nonetheless still a significant factor. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Rocks & Weathering section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Rocks & Weathering essays

  1. Soil is a product of its natural environment and the ways in which humans ...

    Gley soils represent the most extensive soil cover in Scotland. These soils are found on gentler slopes or in areas of high rainfall where the water does not drain away very readily. All the glacial tills of central Scotland are dominated by Gley soils.

  2. glacial eroded landforms

    Glaciated areas offer both constraints and opportunities for settlements. Upland glacial areas have difficulties for settlement because of the rugged terrain and the lack of flat space to build on. As well as the lack of flat land, infrastructure for transport and communication is also more costly to build, as pyramidal peaks and valleys have to be constructed round them in order to connect two settlements.

  1. Distinguish between abrasion and plucking

    This means there is larger erosion from basal debris in the temperate glaciers than in the polar glaciers.

  2. Free essay

    Outline the major landforms associated with Periglacial landscapes and discuss their formation.

    The process sees water expanding inside of the rock which in turn alters the rocks form but it doesn't break its shape. A landform that is created by these freezing processes is that of block fields. These are areas or fields commonly found on hills, are made up of uneven and abrasive blocks.

  1. I am trying to find out how footpath erosion on Pen Y Fan which ...

    This shows that the stones have been uncovered as the hikers have lifted up the mud and grass with their hiking boots and taken it further up or down the Pen Y Fan footpath. *The problem may persist in the future because Pen Y Fan is so easily accessed from

  2. Determining the paleoenviroment and tectonic history of a small area (Cocklawburn Beach)

    Bed 24: This bed is 1.25 metres thick. It has medium sand sized particles, but it is a sandy limestone. This bed shows a return to relatively deep-sea characteristics, but with a high sediment deposition, which suggest a large land mass may have formed nearby. Crinoids are also in this bed, which suggests a deep sea, as the

  1. In this Essay I will inform you of the social, economic and environmental advantages/ ...

    If Calcium didn't exist all this glass would be too expensive even for the seriously rich, and wouldn't be as widely and easily made. Millions of people would be missing an aid to their short/long sightedness and the thermosflask which takes an important role in peoples holidays wouldn't exist, or at least be cheap enough to be worth while.

  2. 'I think that sedimentary stones will be more affected by weathering than igneous stones.' ...

    - Chemical Weathering: is the breakdown of rocks due to chemical reactions, usually involving rainwater. E.g. Calcium carbonate + Carbonic acid (formed when rainwater mixes with carbon dioxide in the air) goes to soluble calcium bicarbonate. Thus minerals in the rock are dissolved and weathered.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work