What is a crescent-shaped sand dune in a desert called?
a) Oasis
b) Barchan
c) Mesa
d) Cliff
Answer: b) Barchan
Explanation
-
Barchan: A barchan (or barkhan) is a mobile, crescent-shaped sand dune with tips or horns that point downwind. They typically form in flat, arid desert areas where wind blows consistently from one primary direction and sand supply is moderate.
-
Characteristics: The gentle slope faces the wind (windward side), while the steeper slope (slip face) sits on the sheltered inner curve of the crescent.
Overview of Other Options
-
a) Oasis: A fertile, watered spot in a desert where underground water reaches the surface, supporting vegetation and human settlement.
-
c) Mesa: An isolated, flat-topped hill or mountain with steep, cliff-like sides, formed by the erosion of horizontal sedimentary strata.
-
d) Cliff: A steep, vertical, or near-vertical rock face formed by the continuous action of weathering and erosion.
