Some important MCQs related to Geological works by Wind With explanations -4

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34. What is the primary cause of desert varnish, a dark coating found on exposed rock surfaces in arid regions?

A) Deposition of wind-blown sand
B) Chemical weathering caused by oxidation and microbial activity
C) Wind abrasion over long periods
D) Formation of a crust due to salt deposition

Answer: B) Chemical weathering caused by oxidation and microbial activity
Explanation:
Desert varnish is a dark coating composed of manganese and iron oxides, formed by the oxidation of these elements with the help of microbes over long periods of time in arid conditions.


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35. The process by which wind carries the finest particles over great distances is called:

A) Deflation
B) Traction
C) Suspension
D) Saltation

Answer: C) Suspension
Explanation:
Suspension involves the movement of fine particles like silt and clay that are carried aloft by wind for long distances, often resulting in dust storms.

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36. Which of the following is a characteristic feature of a desert pavement?

A) Composed of compacted fine-grained particles
B) Formed by the accumulation of loess deposits
C) Consists of closely packed pebbles and stones
D) Found in areas of abundant vegetation

Answer: C) Consists of closely packed pebbles and stones
Explanation:
Desert pavement forms when finer particles are removed by wind, leaving behind a surface covered with pebbles and stones that act as a protective layer against further erosion.

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37. What is the angle of repose for dry sand, which determines the steepness of the leeward side of a sand dune?

A) 15–20 degrees
B) 25–30 degrees
C) 30–34 degrees
D) 40–45 degrees

Answer: C) 30–34 degrees
Explanation:
The angle of repose for dry sand, typically around 30–34 degrees, represents the maximum angle at which sand particles can remain stable without sliding.


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38. Wind-sculpted rocks that have a streamlined shape and smooth surface are known as:

A) Yardangs
B) Ventifacts
C) Zeugen
D) Pediments

Answer: B) Ventifacts
Explanation:
Ventifacts are rocks that have been shaped and polished by wind-driven sand, often resulting in smooth surfaces and sharp edges.

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39. What causes the formation of parallel ridges and grooves on Yardangs?

A) Chemical weathering
B) Variations in rock resistance and wind abrasion
C) Sedimentation by wind
D) Movement of sand dunes

Answer: B) Variations in rock resistance and wind abrasion
Explanation:
Yardangs form in areas where layers of rock with different resistances are subjected to wind abrasion, resulting in parallel ridges and grooves aligned with the prevailing wind direction.

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40. Why do crescent-shaped barchans form in desert regions with limited sand supply?

A) Due to multidirectional winds
B) Due to strong, consistent winds and hard ground
C) Because of vegetation holding the sand in place
D) Due to the presence of fine-grained sediments

Answer: B) Due to strong, consistent winds and hard ground
Explanation:
Barchans form in areas with strong, unidirectional winds, a limited sand supply, and a firm ground surface, resulting in crescent-shaped dunes that migrate in the wind direction.

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41. Which of the following is NOT an example of a wind depositional feature?

A) Loess
B) Barchan
C) Seif dune
D) Yardang

Answer: D) Yardang
Explanation:
Yardangs are erosional features formed by wind abrasion, while loess, barchans, and seif dunes are depositional features.


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42. What type of landform is formed when wind removes loose, fine particles and leaves behind a flat, rocky surface?

A) Playa
B) Reg (Desert pavement)
C) Erg
D) Inselberg

Answer: B) Reg (Desert pavement)
Explanation:
Desert pavement, or reg, forms when wind removes fine particles by deflation, leaving a flat, rocky surface composed of larger pebbles and stones.

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43. What is the primary mechanism for sand movement in a process called saltation?

A) Rolling and dragging of sand grains along the surface
B) Lifting of sand grains into suspension
C) Bouncing of sand grains due to wind force
D) Collision of sand grains with other particles

Answer: C) Bouncing of sand grains due to wind force
Explanation:
Saltation involves the bouncing movement of sand grains lifted by wind and then falling back to the surface, transferring energy to other particles and initiating further movement.

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44. Which of the following conditions promotes the formation of loess deposits?

A) Proximity to deserts with abundant sand supply
B) Areas downwind of glacial outwash plains
C) High rainfall and dense vegetation
D) Steep mountain slopes

Answer: B) Areas downwind of glacial outwash plains
Explanation:
Loess deposits are composed of fine silt and clay transported by wind, often originating from glacial outwash plains where glacially ground sediments are exposed and easily picked up by the wind.


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45. What is the primary characteristic of a parabolic dune?

A) Crescent-shaped with horns pointing downwind
B) Crescent-shaped with horns pointing upwind
C) Elongated and parallel to the wind direction
D) Irregularly shaped with no definite orientation

Answer: B) Crescent-shaped with horns pointing upwind
Explanation:
Parabolic dunes form in areas with some vegetation. The horns of the dune point upwind as vegetation anchors the sand, while the central part of the dune moves downwind.

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