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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pseudosymmetry (pseu-do-sym'-me-try). Apparent symmetry of a crystal, resembling that of another system; it is often due to twinning.

intervalometer (in''-ter-val-om'-e-ter). A timing device on an aerial camera that automatically operates the shutter at predetermined intervals.

plunging breaker (plung'-ing). A type of breaker whose crest curls over and collapses suddenly, with complete disintegration of the wave. Cf: surging breaker; spilling breaker.

cataclast (cat'-a-clast). A megacryst that is a remnant of incomplete cataclasis.

adductor ridge . A linear elevation that develops (in association with an adductor pit ) on the interior of a scutum of certain cirripede crustaceans (such as Balanomorpha).

hole [coast] . A term used in New England and England for a small bay, cove, or narrow waterway; e.g. Woods Hole, Mass. and Mousehole, Cornwall, U.K.

periglacial (per-i-gla'-cial). (a) Said of the processes, conditions, areas, climates, and topographic features at the immediate margins of former and existing glaciers and ice sheets, and influenced by the cold temperature of the ice. (b) By extension, said of an environment in which frost action is an important factor, or of phenomena induced by a periglacial climate beyond the periphery of the ice. Syn: cryergic; cryonival; paraglacial; subnival. Term introduced by Lozinski (1909).

compensator . An apparatus in a polarizing microscope that measures the phase difference between two components of polarized light, e.g. a Berek compensator or a biquartz plate.

Unwin's critical velocity (Un'-win's). critical velocity (e).

motukoreaite (mo-tu'-ko-rea'-ite). A white to pale yellow-green rhombohedral mineral related to hydrotalcite: [Mg6Al3(OH)18][Na0.6(SO4,CO3)2]•12H2O .

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