spondylium duplex . A spondylium formed by convergence of dental plates and supported by variably developed median septum arising from the floor of the pedicle valve.
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.
isofract (i'-so-fract). A graphic representation of the locus of all compositions in a system having a given value for the index of refraction.
tongue [ice] . A projection of the ice edge up to several kilometers in length, caused by wind and current.
gyrocone (gy'-ro-cone). A loosely coiled cephalopod shell in which the successive whorls are not in contact with each other, or in which only a single whorl is approximately completed. Also called: gyroceracone.
plug [drill] . n. A watertight or gastight seal, such as an interval of cement or a bridge plug, installed in a borehole or well to prevent movement of fluids. v. To set a plug in a borehole; to fill in or seal off fractures, cavities, or other pores in the walls of a borehole.
peak-ring crater . A complex impact crater with a central mountainous ring, instead of a central peak, surrounding its center. Peak-ring craters are generally larger than central-peak craters on a given planet or satellite. The radial profile of the ring is roughly symmetric, as opposed to that of a multi-ring crater.
azonal soil . In the 1938 soil-classification system, one of the three soil orders. Azonal soils lack distinct genetic horizons and resemble the parent material (USDA, 1938). Not used in current U.S. system of soil taxonomy. Cf: intrazonal soil; zonal soil; Entisols. Syn: immature soil.
underconsolidation (un''-der-con-sol''-i-da'-tion). Consolidation (of sedimentary material) less than that normal for the existing overburden; e.g. consolidation resulting from deposition that is too rapid to give time for complete settling. Ant: overconsolidation.
geologic age . (a) The age of a fossil organism or of a particular geologic event or feature referred to the geologic time scale and expressed in terms either of years or centuries ( absolute age ) or of comparison with the immediate surroundings ( relative age ); an age datable by geologic methods. (b) The term is also used to emphasize the long-past periods of time in geologic history, as distinct from present-day or historic times. Cf: age [geochron].
node [bot] . The place on a plant stem from which a leaf and bud normally emerge.
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