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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tiptopite (tip'-top-ite). A colorless hexagonal mineral: K2(Li,Na,Ca)6Be6(PO4)6(OH)2•H2O . It is structurally related to the cancrinite group.

striation (stri-a'-tion). (a) stria. (b) One of multiple scratches or minute lines, generally parallel, inscribed on a rock surface by a geologic agent, e.g., glaciers ( glacial striation ), streams (cf: drag mark ), or faulting (cf: slickenside ). Syn: scratch. (c) The condition of being striated; the disposition of striations. Adj: striated; striate.

linkage [geomorph] (link'-age). The joining at a sharp angle of two branches of a mountain range, as shown in plan view. Cf: deflection [geomorph].

acute bisectrix (a-cute'). In optically biaxial minerals, the direction bisecting the acute angle between optic axes. Cf: obtuse bisectrix.

confining bed (con-fin'-ing). A body of relatively impermeable or distinctly less permeable material stratigraphically adjacent to one or more aquifers. Cf: aquitard; aquifuge; aquiclude. Syn: confining unit .

tracheophyte (tra'-che-o-phyte''). A vascular plant; includes all plants that have a vascular system, i.e. xylem and phloem (Swartz, 1971, p.477).

step drawdown test . A type of aquifer test in which the water level in a pumped well is measured while the well is pumped at a constant rate for a given period of time; the pumping rate is successively increased for each of several time intervals, the water level is measured during each interval, and drawdown is calculated for each pumping rate. The derived relationship between drawdown and pumping rate can be used to estimate aquifer properties, the practical yield of the pumping well, and the appropriate depth setting of the pump in a production well.

medenbachite . A yellow to brownish-yellow triclinic mineral: Bi2Fe3+(Cu,Fe2+)O(AsO4)2(OH)3.

hurricane (hur'-ri-cane). A tropical cyclone, esp. in the North Atlantic and eastern North Pacific basins, in which the sustained near-surface wind speed equals or exceeds 64 knots (73 mph). See also: typhoon.

wodanite (wo'-da-nite). A variety of biotite containing titanium.

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