Question

Which of the following types of dunes form(s) primarily by uni-directional wind?

• A. Linear dunes
• B. Parabolic dunes
• C. Barchan dunes
• D. Barchan dunes

Answer 1

The Correct Option is B, C

To understand which types of sand dunes are formed primarily by uni-directional winds, we need to examine the characteristics of different dunes:

1. Linear Dunes:

   These dunes are typically straight or slightly sinuous sand ridges that can extend for great lengths. They form under bidirectional wind regimes, where the wind comes from two distinct directions. Hence, linear dunes are not mainly formed by uni-directional winds.

2. Parabolic Dunes:

   Parabolic dunes have a U-shape with the open end facing away from the wind direction. These dunes typically form in areas where vegetation is present, stabilizing some parts of the dune. They are associated with uni-directional winds, where the consistent wind direction pushes the sand into the parabolic shape. Therefore, parabolic dunes form primarily by uni-directional winds.

3. Barchan Dunes:

   Barchan dunes are crescent-shaped with the tips or "horns" pointing downwind. These dunes form in flat, arid regions with a limited supply of sand, and they are shaped by steady, strong uni-directional winds. The convex side of the dune faces the wind, which continuously moves sand over the dune crest. Thus, barchan dunes are also formed mainly by uni-directional winds.

Based on the above analysis, the dunes that form primarily by uni-directional winds are Parabolic dunes and Barchan dunes. These types are correctly identified in the options provided.