RFG 2018 Conference

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.

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infiltration vein . An interstitial mineral deposit formed by the action of percolating waters. Cf: segregated vein.

culvert (cul'-vert). Any covered structure, not classified as a bridge, that constitutes a transverse drain, waterway, or other opening under a road, railroad, canal, or similar structure.

horse [struc geol] . A displaced block of rock that is bounded on all sides by faults.

tideland (tide'-land). (a) The coastal area that is alternately covered and uncovered by the ordinary daily tides; land that is covered by tidewater during a flood tide. (b) Land that underlies the ocean beyond the low-water mark, but within the territorial waters of a nation. The term is often used in the plural.

coombsite . A vitreous brown rhombohedral mineral: K(Mn2+,Fe2+,Mg)13(Si,Al)18O42(OH)14. It is an isotype of zussmannite.

compaction [soil] . (a) Any process, such as burial or desiccation, by which a soil mass loses pore space and becomes denser. (b) The densification of a soil by mechanical means, accomplished by rolling, tamping, or vibrating, usually at controlled water content. Cf: consolidation [eng].

aerosol (aer'-o-sol). A sol in which the dispersion medium is a gas (usually air) and the dispersed or colloidal phase consists of solid particles or liquid droplets; e.g. mist, haze, most smoke, and some fog.

division [sed] . A portion of a bed [geomorph] that is distinguished from other parts of the bed by the presence of a specific type of sedimentary structure (Blatt et al., 1980).

Rosiwal analysis (Ro'-si-wal). In petrography, a quantitative method of estimating the volume percentages of the minerals in a rock. Thin sections of a rock are examined with a microscope fitted with a micrometer which is used to measure the linear intercepts of each mineral along a particular set of lines. This method "is based on the assumption that the area of a mineral on an exposed surface is proportional to its volume in the rock mass" (Nelson and Nelson, 1967, p.320).

Rg wave . A slow, short-period Rayleigh wave that travels only along a nonoceanic path. The "g" refers to the granitic layer. Cf: Lg wave.

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