Dust wall
From Glossary of Meteorology
dust wall
The leading edge of a duststorm, which looks like a knobby vertical or convex wall when viewed from the clear air ahead of the storm.
Sharply defined dust walls are caused by gust fronts at the leading edge of thunderstorm straight-line outflow winds along the surface. Sometimes surface friction will slow the air immediately touching the surface resulting in a dust wall that curves back at the bottom.
See also haboob.
See also haboob.