| 单词 | desert varnish |
| 释义 | > as lemmasdesert varnish desert varnish n. a dark-coloured film composed of iron and manganese oxides, usually with some silica, deposited on exposed rocks in the desert and becoming polished by wind abrasion. ΚΠ 1904 C. R. Van Hise Treat. Metamorphism (U.S. Geol. Surv.) 547 In arid regions the hardened film has frequently been smoothed by the wind-blown sand, so as to present a polished surface. Such polished hardened films are known as ‘desert varnish’. 1944 A. Holmes Princ. Physical Geol. xiii. 270 The loose salts are blown away, but oxides of iron, accompanied by traces of manganese and other similar oxides, form a red, brown, or black film which is firmly retained. The surfaces of long-exposed rocks and pebbles thus acquire a characteristic coat of ‘desert varnish’. 1970 R. J. Small Study of Landforms ix. 294 Capillary rise is associated with the chemical breakdown of the interior of large boulders and the deposition of a hard crust of ‘desert varnish’..on their surface. < as lemmas |
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