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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crevice (crev'-ice). (a) A narrow opening or recess, as in a wave-eroded cliff or glacier. (b) A colloquial syn. of crevasse.

exocyathoid expansion (ex-o-cy'-a-thoid). Growth of an additional intervallum in an archaeocyathid cup, which appears to have had an adherent function (TIP, 1972, pt. E, p.7).

peg-leg multiple . A multiple reflection involving successive reflection at different interfaces so that its travel path is not symmetrical. Sometimes refers to short-path multiples within thin beds, which result in transferring energy from the front of a wavetrain and adding it back later, and sometimes to long-path multiples, which lead to separate events.

fels . A rarely used term applied to massive metamorphic rock lacking schistosity or foliation, e.g., calcsilicate fels (Winkler, 1967). Cf: granofels.

rock train . A term suggested by Kendall and Wroot (1924, p.448) for the rock material in "process of transport at the sides and in the middle of a glacier" and "subject to the dynamic forces of the glacier".

transposition . In structural petrology, disruption of preexisting fabric so that all fabric elements are rotated to a new orientation. Results in a transposition or transposed foliation.

pleural furrow . (a) A groove along the surface of a pleura of a trilobite. (b) A groove crossing the pleura of a merostome.

vanuralite (van-ur-al'-ite). A citron-yellow monoclinic mineral: Al(UO2)2(V2O8)(OH)•11H2O .

imbibition [rock] (im-bi-bi'-tion). Formation of feldspathic minerals by the penetration of alkaline solutions of magmatic origin into aluminum-rich metamorphic rocks. Obsolete.

Eophytic (E-o-phyt'-ic). A paleobotanic division of geologic time, signifying that time during which algae were abundant. Cf: Aphytic; Archeophytic; Cenophytic; Mesophytic; Paleophytic.