Desert Varnish


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Related to Desert Varnish: Rock varnish

desert varnish

[¦dez·ərt ′vär·nish]
(Geology)
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Desert Varnish

 

a thin (0.5–5 mm) dark brown or black stain or crust on rock surfaces, including cliffs, boulders, and pebbles, in the desert. It consists of oxidized manganese and iron compounds precipitated from a solution that rises to the surface by capillarity as a result of the abrupt changes in rock temperature in the course of the 24-hour day.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Like desert varnish, life on Titan may have unfamiliar pacing that could prevent Earthlings from determining whether azotosomes or other membranous bubbles found in that moon's methane oceans actually harbor life.
Caption: Desert varnish, which tints rocks a burnt orange or black (left, Angel Arch, Canyonlands National Park, Utah), may be produced by unknown living organisms.
Some of these were covered in desert varnish. This material is potentially dateable.
This rockshelter has deeply patinated, pecked circle and track engravings which are coated in desert varnish. Desert varnish has been dated on other Panaramitee engraving sites to between 10 000 and 30 000 years ago (Dragovich 1986; Nobbs & Dorn 1988, 1993--although see also Krinsley et al.
The petroglyph group used brushes to make a desert varnish on their rocks.
Photo: Stained with "desert varnish,' Navajosandstone forms nearly perfect 290-foot-high arch of Rainbow Bridge
In some eases, the laser scans picked up the faint traces of ancient petroglyphs that couldn't be seen with the naked eye because they were obscured by a fresh coat of desert varnish, says Wasklewiez.--S.P.
One testament to the age and stability of some desert pavements is the desert varnish that coats only the upward-facing exposed surfaces of the pebbles.
Scientists have developed a quick, easy, portable, and nondestructive way to determine the age of desert varnish, the mysterious dark coating that slowly develops on rocks in many arid regions of the world (see p.
Desert varnish is rich in iron oxides and manganese oxide--both possible products of biological processes--and contains varying amounts of clay, says Nicholas E.