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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barometric leveling . A type of indirect leveling in which differences of elevation are determined from differences of atmospheric pressure observed with altimeters or barometers. Cf: thermometric leveling.

coherent diffracting domain . The volume of crystal that is without defects and yet sufficiently large to serve as a diffraction grating, producing a coherent X-ray beam (Klug and Alexander, 1974, chap.9). Sometimes called "coherent scattering domain." Abbrev: CDD.

ciliate (cil'-i-ate). n. Any protozoan belonging to the class Ciliata and characterized by the presence of cilia throughout its life cycle. Range, Upper Jurassic to Holocene. adj. Possessing cilia.

mosandrite (mo-san'-drite). A colorless, greenish, reddish-brown, or yellowish-brown monoclinic mineral: (Na,Ca)3(Ca,Ce)3(Ti,Nb,Al,Zr)(Si2O7)2(O,F)4. Cf: johnstrupite. Syn: rinkite; rinkolite; lovchorrite; khibinite [mineral].

halokinesis (hal-o-ki'-ne-sis). (a) The deformation of halite by flowage. Mechanisms cited for this process include gravity flow, tectonic thrusting, and diapirism (Kyle and Posey, 1991). Syn: salt tectonics. (b) Form of salt tectonics in which salt flow is powered entirely by gravity that is, by release of gravity potential energy alone, in the absence of significant lateral tectonic forces (Jackson and Talbot, 1991).

rhythmic crystallization (rhyth'-mic). A phenomenon, observed in igneous rocks, in which different minerals crystallize in concentric layers, giving rise to orbicular structure. See also: cyclic crystallization.

beef . A quarrying term, used originally in Purbeck, southern England, for thin, flat-lying veins or layers of fibrous calcite, anhydrite, gypsum, halite, or silica, occurring along bedding planes of shale, giving a resemblance to beef. It appears to be due to rapid crystallization in lenticular cavities.

knitted texture (knit'-ted). A texture that is typical of the mineral serpentine in a rock when it replaces a clinopyroxene. Cf: lattice texture [meta].

Earth tide . The response of the solid Earth to the forces that produce the tides of the sea; semidaily Earth tides have a fluctuation of between seven and fifteen centimeters (Strahler, 1963, p.110-111). Syn: bodily tide.

laqueiform (la-que'-i-form). Said of the loop pattern in a dallinid brachiopod (as in the family Laqueidae) in which posterior connecting bands from the ascending branches to the descending branches "are retained during enlargement and proportional thinning during change from frenuliniform to terebrataliiform loop" (TIP, 1965, pt. H, p.147).

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