scum . A film that floats on a liquid, such as a stagnant pool. The film may be composed of soap, of precipitated calcium carbonate, or of putrid matter.
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.
orthotriaene (or-tho-tri'-aene). A sponge triaene in which the cladi are oriented close to 90 degrees to the rhabdome. Cf: protriaene.
active channel . (a) A channel presently containing flow on a plain or valley bottom with multiple generations of channels. (b) The portion of a channel in which flow is present at the time of measurement, as opposed to the high-flow channel.
permeability [geol] (per''-me-a-bil'-i-ty). The property or capacity of a porous rock, sediment, or soil for transmitting a fluid; it is a measure of the relative ease of fluid flow under unequal pressure and is a function only of the medium. The customary unit of measurement is the millidarcy. Cf: absolute permeability; effective permeability; relative permeability; hydraulic conductivity. Syn: perviousness. Adj: permeable. Ant: impermeability.
torus (to'-rus). (a) An invagination or protuberance of exine more or less paralleling the laesura of a spore. Cf: kyrtome. (b) The thickening of the closing membrane in a bordered pit.
rational face (ra'-tion-al). A crystal face naturally suggested by and peculiar to the internal molecular structure of the mineral species to which the crystal belongs. Such faces usually have low Miller indices.
didymospore (did'-y-mo-spore). An asexual fungal spore with both transverse and longitudinal septa which produce a pattern reminiscent of a brick wall. Cf: Saccardoan spore groups.
enfilade (en'-fi-lade''). (a) A fire that can rake a line of troops. (b) A position exposed to direct fire. See also: defilade .
insequent (in'-se-quent). adj. Said of a stream, valley, drainage system, or type of dissection that is seemingly uncontrolled by the associated rock structure or surface features, being determined by minor inequalities not falling into any larger-scale pattern. Etymol: in + consequent. Syn: inconsequent. n. insequent stream.
elevator tectonics (el'-e-va''-tor). A rarely used term introduced by Dietz and Holden (1966, p.353) for the rise and fall of blocks of sialic crust from surficial to abyssal levels or vice versa.
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