Layers in the lower West Flank of Arsia Mons (Absolute Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)

Caption NASA:"This image - dated July, 18th, 2007) covers a Pit in the lower West Flank of Arsia Mons, one of the four Giant Volcanoes of the Tharsis Volcanic District.
Many Layers are exposed in the Pit, probably marking individual Lava Flows, and they can provide useful information about the nature of some of the many Martian Volcanic Eruptions.

This image was acquired in the middle of a large Regional Dust Storm, but the Atmosphere over this image is only moderately dusty because the altitude is 6,5 Km higher than the Planetary Mean, so the air is quite thin and cannot hold as much Dust. Although the Atmosphere was not too dusty, the Surface is buried by a Dust Layer which is probably several meters thick.
These high-altitude locations on Mars have thick Dust Deposits because the thin air cannot blow away the Dust, or at least not as fast as it accumulates. On Earth the oceans serve as "Dust Traps", but on Mars, it is a job for the highest Volcanoes".