RAS question
The crescent-shaped sand dunes found in the Thar Desert of Rajasthan are known as:
Correct answer: (A) Barchans.
The crescent-shaped sand dunes found in Rajasthan's Thar Desert are known as barchans, and their horns point downwind.
Explanation
Barchans are identified by their crescent shape and horns that point downwind. In Rajasthan, these dunes occur in the Thar Desert, especially around Jaisalmer and Barmer. They form where moderate winds blow steadily from one direction across a nearly even sandy surface. Therefore, both the crescent shape and the direction of the horns identify Option A as the answer.
Why the other options are wrong
- (B) Star dunes have multiple arms radiating from a central peak, so their form is different from the single crescent shape of barchans.
- (C) Longitudinal dunes are elongated and aligned parallel to the wind, not crescent-shaped with horns pointing downwind.
- (D) Parabolic dunes are U-shaped with arms pointing upwind, the opposite orientation from barchans.
Concept
Wind-shaped desert landforms are identified through dune shape and wind direction. RAS geography repeatedly connects Thar Desert features with their physical processes.