What are the hills of sand created by wind in deserts called?
a) Cliffs
b) Sand Dunes
c) Canyons
d) Plateaus
Answer: b) Sand Dunes
Explanation
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Sand Dunes: A sand dune is a mound, hill, or ridge of loose sand piled up and shaped by the wind (aeolian process).
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Formation: Dunes form when wind carries sand grains and encounters an obstacle (like a rock, bush, or elevation change), causing the wind to slow down and drop its sediment load.
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Key Types of Sand Dunes:
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Barchans: Crescent-shaped dunes with points (horns) pointing downwind, common in the Thar Desert.
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Seif / Longitudinal Dunes: Long ridges of sand aligned parallel to the prevailing wind direction.
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Transverse Dunes: Asymmetrical sand ridges running perpendicular to the wind direction.
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Overview of Other Options
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a) Cliffs: Vertical or steep rock faces created by weathering, erosion, or tectonic faulting (commonly coastal or river cliff landforms).
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c) Canyons: Deep, narrow valleys with steep cliff sides cut into the earth by running river water over millions of years (e.g., Grand Canyon, Gandikota Canyon in Andhra Pradesh).
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d) Plateaus: Broad, flat-topped elevated landforms rising sharply above the surrounding land on at least one side (e.g., Deccan Plateau).
