Question

The sand supply and the variability of wind direction result in different dune types. In the options below, choose the CORRECT pair of dune types marked I and II in the figure.

• A. I – Transverse dune; II – Barchan dune
• B. I – Star dune; II – Barchan dune
• C. I – Barchan dune; II – Linear dune
• D. I – Barchan dune; II – Star dune

Hint:

Star dunes form under multi-directional winds, while Barchan dunes form under unidirectional winds with a moderate sand supply.

Answer 1

The Correct Option is B

The figure provided shows the relationship between sand supply and wind direction variability. Dunes are formed based on wind direction and sand supply. Here's a detailed explanation of the dunes:
- Star Dune: Star dunes form in areas where the wind direction is highly variable (multi-directional winds). The sand supply is generally abundant, and the dunes have a complex shape with multiple arms radiating from a central point. This matches the characteristics of dune type I, which is formed under multi-directional wind conditions.
- Barchan Dune: Barchan dunes form in regions with a predominant unidirectional wind (wind blowing mostly in one direction). These dunes have a crescent shape with the horns pointing downwind. Barchan dunes are typically formed in areas where the sand supply is moderate and the wind direction is consistent. This matches the characteristics of dune type II in the figure, which is formed under unidirectional wind conditions.
Thus, the correct answer is (B) I – Star dune; II – Barchan dune.