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In this lesson we are going to discuss about the resultant features of wind deposition in arid areas

Answer Text:
Resultant Features of Wind Deposition
1. Sand Dunes
Dune - Low ridge of sand accumulated by wind deposition.
Types
i) Barchans

- Crescent shaped mound of sand in a desert.
- Sand accumulates around an obstacle lying on the path of wind.
- Deposition continues making the mound to grow bigger.
- Wind blows sand over leeward side creating smooth gentle windward slope.
- Wind eddies act on the leeward slope making it to be steep and concave in shape.
- Side wind move the sand grains on the sides forward creating the two edges which are curved e.g. in Sahara and Arabian Deserts.
Characteristics
a) Crescent/moon shaped
b) Smooth gentle windward slope
c) Steep concave leeward slope
d) Horns or 2 curved edges
e) Occurs individually or in groups

ii) Seif Dunes

- Ridge shaped mounds of sand lying parallel to the path of prevailing wind.
- Wind blows between barchan dunes.
- Wind eddies move sand towards the sides.
- Sand accumulates on the sides resulting into ridge shaped mounds e.g. in Namib Desert.
iii) Transverse/Wake Dunes

- Wave like mounds of sand in a desert which lie at right angles to the prevailing wind.
- Less strong winds blow over sand from one direction.
- The wind concentrates larger grains of sand into series of transverse ridges.
- Wind may continue pushing the sand causing it to accumulate on the leeward side to form wake dune e.g. in W. Sahara.
2. Drass
- Biggest sand features in a desert with surface resembling a plateau and with a height of up to 200m.
- Barchans and Seif dunes may form on such features e.g. in E. Sahara desert.
3. Loess
- Fertile soils with great thickness of about 100m formed from deposition of dust from deserts.
- Dust from deserts is carried beyond to wet areas.
- It’s washed down by rain causing its deposition.
- It accumulates into layers.
- Deposition continues and the layers are compacted forming sedimentary rocks.
- The sedimentary rocks wither to form fertile soils which favour cultivation e.g. Temperate lands of Europe along Rhine valley from Sahara
dusts and along Huang He valley in N. China from dust of Gobi desert.