What weather phenomenon is indicated by a wall of dust?

A wall of dust is specifically associated with a dust storm. This phenomenon occurs when strong winds lift loose, dry soil and dust particles into the air, creating a dense barrier of dust that can significantly reduce visibility and have detrimental effects on both health and the environment. Dust storms are common in arid and semi-arid regions, where vegetation is sparse and loose soil can easily be disturbed by high winds.

In contrast, a hailstorm involves the formation of ice pellets in storm clouds and does not produce a wall of dust. A sandstorm is similar to a dust storm but typically involves sand, rather than finer dust particles, and occurs in desert environments. A tornado is a rapidly rotating column of air that can cause extensive damage but does not manifest as a wall of dust like a dust storm does.

Thus, the presence of a wall of dust distinctly points to a dust storm as the correct answer.