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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englacial drift . Rock material contained within a glacier or ice sheet.

boothite (booth'-ite). A blue monoclinic mineral: CuSO4•7H2O . Its blue color is lighter than that of chalcanthite. It dehydrates to chalcanthite in air.

joint set . A group of more or less parallel joints. See also: joint system.

slip [geomorph] . A narrow mountain pass; a defile.

refoliation (re''-fo-li-a'-tion). A foliation that is subsequent to and oriented differently from an earlier foliation.

data dictionary . A database that serves as a catalogue containing information about map features or attributes. The catalogue may define data file and element names, sources, accuracy, date of entry or update, or other characteristics of the data and its sources.

permeability [soil] . (a) The ease with which gases, liquids, or plant roots penetrate or pass through a bulk mass of soil or a layer of soil. Because different soil horizons vary in permeability, the particular horizon under question should be designated. (b) The property of a porous medium itself that expresses the ease with which gases, liquids, or other substances can flow through it, and is the same as intrinsic permeability.

micropiracy (mi-cro-pi'-ra-cy). The overtopping and breaking-down of the narrow ridge between adjacent rill channels, and diversion of flow from the higher, shorter, and shallower channel to the lower, longer, and deeper one closer to the initial rill (Horton, 1945, p.335). See also: cross-grading.

stable [radioactivity] (sta'-ble). Said of a substance that is not spontaneously radioactive. Cf: unstable [radioactivity].

dating (dat'-ing). Age determination of naturally occurring substances or relicts by any of a variety of methods mostly based on the amount of change, happening at a constant and measurable rate, in a component. The changes may be chemical, or induced or spontaneous nuclear.

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