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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phototriangulation (pho''-to-tri-ang''-u-la'-tion). The addition of horizontal and/or vertical control points by photogrammetric methods, whereby "the measurements of angles and/or distances on overlapping photographs are related into a spatial solution using the perspective principles of the photographs" (ASP, 1966, p.1148); esp. aerotriangulation.

fuel-coolant interaction . Referring to an industrial analog to a phreatomagmatic explosion, involving a fuel such as molten iron and a coolant such as water. The interaction of the fuel and coolant has resulted in vapor explosions in industrial environments. Abbrev: FCI.

macphersonite (mac-pher'-son-ite). A pale amber, colorless or white orthorhombic mineral: Pb4(SO4)(CO3)2(OH)2 . It is a polymorph of susannite and leadhillite.

weir . (a) A small dam in a stream, designed to raise the water level or to divert its flow through a desired channel; e.g., a "leaping weir". (b) A notch in a levee, dam, embankment, or other barrier across or bordering a stream, through which the flow of water is regulated; e.g., a "wasteweir". Well-designed weirs usually have known dimensions and cross-section areas as a function of height above the base. Graduations of height allow rapid determination of hydraulic parameters, such as wetted perimeter, needed to calculate discharge.

structural province . A region whose geologic structure differs significantly from that of adjacent regions. It is generally coextensive with a physiographic province.

litharge (lith'-arge). A red or yellow tetragonal mineral: PbO . Cf: massicot. Syn: lead ocher. It is the Pb analogue of romarchite.

super-solidus intrusion breccia PGE deposit . A mineral-deposit type characterized by platinum-group element sulfide mineralization cutting mafic-ultramafic cumulates associated with an intrusive breccia formed by associated ultramafic dikes. Abbrev: SIB-type PGE deposit.

pull-apart basin . A topographic depression created by an extensional bend or extensional overstep along a strike-slip fault (Aydin and Nur, 1982). Syn: sag pond; rhombochasm.

minerocoenology (min''-er-o-coe-nol'-o-gy). The study of mineral associations in the broadest sense, such as the correlation of igneous rocks or magmatic provinces with their ore deposits (Thrush, 1968, p.712). Obsolete.

self-reversal (self-re-ver'-sal). Acquisition by a rock of a natural remanent magnetization opposite to the ambient magnetic field direction at the time the rock was formed.


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