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Upper Left: A vertical face at Canyon de Chelly, Arizona, is streaked with heavy metal skins, iron films, lithobiont coatings, oxalate crusts, rock varnish, and silica glaze.
Upper Right: Lava flows in the arid regions of Mauna Loa show a distinct color change within decades as a direct result of accumulation of silica glaze.
The main Petra tourist attraction of the Al-Khazneh Tomb façade is coated with a black manganese-rich varnish, allowing the carved portions of the elaborate burial chamber to stand out.
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The thickness of varnish has been used to ‘date’ geomorphological features, such as glacial moraines, debris flows, and overturned boulders.
The almost white colour of Ayers Rock is coated by mostly iron-clay orange accretions, facilitating photogenic displays.
Dramatic sandstone escarpment faces of the Colorado Plateau in such places as Monument Valley are frequently coated by a reddish-brown silica glaze formed inside the unopened joint fracture and then exposed by block wasting. Rock coatings change the appearance of bare rock landforms.
This chapter focuses on an irony, that the supposed fundamental bare-rock nature of desert landforms stretches the truth.