RS110
Residents of Amnu maintained not only travelers to the White Mesas, but the mesas themselves; one of the most continual and exhausting tasks was in keeping the cliff faces nearly ash-free through the use of tools, solvents, and well-developed climbing muscles. Of course, with only a few dozen able-bodied workers, keeping hundreds of square miles free of a ubiquitous airborne particulate would have been an impossible task, and as such only a few especially-breathtaking formations remained a focus.
It is a testament to the dedication of Amnu that those formations even today seem somewhat cleaner of ash than the surrounding desert.