topographic feature . A prominent or conspicuous topographic form or noticeable part thereof (Mitchell, 1948, p.80). Cf: physiographic feature.
GeoWord of the Day
The GeoWord of the Day is a free service of the American Geosciences Institute. All of the terms and definitions are from the Glossary of Geology, 5th Edition Revised.
gemstone (gem'-stone). Any mineral or rock that, when cut and polished, has sufficient beauty, rarity, and durability for use as a personal adornment or other ornament. Organic materials such as pearl are considered gem materials rather than gemstones.
rheoplast (rhe'-o-plast). A sedimentary structure resembling common sole mark, produced as a result of liquefaction, diapirism, and rheoplasis during compaction (Van de Poll and Patel, 1981).
chain coral . Any coral (esp. one belonging to the family Halysitidae) characterized, in plan view, by cylindrical, oval, or subpolygonal corallites joined together on two or three sides to form a branching, chainlike network.
gelifluction (gel-i-fluc'-tion). The progressive lateral flow of earth material under periglacial conditions; solifluction in a region underlain by frozen ground. It is commonly used as a modifying or combining term with bench, lobe, sheet, slope, and stream to indicate periglacial origin by soil flow. Also spelled: gelifluxion. Syn: congelifluction.
zone symbol . The symbol of the zone axis of a crystal in terms of the crystal lattice, e.g. the symbols for the zone axis of a series of ( hk 0) faces would be [001]. Cf: indices of lattice row.
baumstarkite . A metallic black triclinic mineral: Ag3Sb2(Bi,Sb)S6.
campanite (cam'-pa-nite). An extrusive rock originally described as a tephrite containing large leucite crystals, and later defined as a pseudoleucite-bearing extrusive equivalent of nepheline syenite (Johannsen, 1939, p.245); Tröger considered it the extrusive equivalent of essexite-foidite (Streckeisen, 1967, p.208). Obsolete.
argentopentlandite (ar''-gen-to-pent'-land-ite). A metallic bronze-brown cubic mineral: Ag(Fe,Ni)8S8 . A silver-bearing member of the pentlandite group.
sepic plasmic fabric . In soil micromorphology, the appearance of the fine-grained part of a soil in petrographic thin section viewed under cross nicols as wisps or streaks of highly oriented and birefringent clay in a less organized dark matrix. A characteristic microfabric of soils.
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