Seif dunes are wind-blown deposits that extend parallel to what?

Seif dunes are wind-blown deposits that extend parallel to what?

• A. River flow direction
• B. Mountain slope
• C. The prevailing wind
• D. The ocean current

Answer: (C)

Seif dunes are long, narrow sand ridges that form where a strong, steady wind moves sand predominantly in one direction. The grains are transported by saltation and creep along that wind path, building crests that run parallel to the wind. Because the sand accumulates along the wind direction rather than across it, these dunes extend parallel to the prevailing wind. The other options don’t set dune orientation in desert interiors—their formation is controlled by wind, not by river flow, mountain slope, or ocean currents. So the key idea is that wind direction dictates the alignment of seif dunes.

Seif dunes are long, narrow sand ridges that form where a strong, steady wind moves sand predominantly in one direction. The grains are transported by saltation and creep along that wind path, building crests that run parallel to the wind. Because the sand accumulates along the wind direction rather than across it, these dunes extend parallel to the prevailing wind. The other options don’t set dune orientation in desert interiors—their formation is controlled by wind, not by river flow, mountain slope, or ocean currents. So the key idea is that wind direction dictates the alignment of seif dunes.