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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smrkovecite . A white or yellow monoclinic mineral of the atelestite group: Bi2O(OH)PO4.

cenozonite . An alternative term for assemblage zone (Henningsmoen, 1961, p.68).

blackjack [coal] (black'-jack). (a) A thin stratum of coal interbedded with layers of slate; a slaty coal with a high ash content. (b) A British term for a variety of cannel coal. Also spelled: black jack.

earthquake moment . A measure of the size of an earthquake relating to the force couples across the area of fault slip. See: seismic moment.

boundary survey . A survey made to establish or re-establish a boundary line on the ground or to obtain data for constructing a map showing a boundary line; esp. such a survey of boundary lines between political territories. Cf: land survey; cadastral survey.

metastibnite (met-a-stib'-nite). A red noncrystalline mineral: Sb2S3 . It is an amorphous form of stibnite.

friction head . That head of fluid which is lost because of friction. See also: friction slope. Syn: head loss; friction loss.

dorsal (dor'-sal). (a) Pertaining to, or situated near or on, the back (not the hind end) or upper surface of an animal or of one of its parts; e.g. toward the brachial valve from the pedicle valve of a brachiopod, or pertaining to the hinge region of the shell of a bivalve mollusk, the side of the uniserial stipe opposite the thecal apertures of a graptoloid, or the spiral side of a trochoid foraminifer. (b) Referring to the direction or side of an echinoderm away from the mouth, normally downward and outward, e.g. toward the point of attachment of the column with blastoid theca or to the part of the crinoid or cystoid calyx located toward the column; aboral. (c) In vertebrates, toward the part of the animal that bears the spinal cord (rather than toward the belly). Ant: ventral.

deltaite (del'-ta-ite). A mixture of crandallite and hydroxylapatite.

conveyor-belt model . A three-dimensional depiction of a mature extratropical cyclone and its corresponding fronts in terms of three interacting airstreams, often referred to as conveyor belts. This model developed out of a better understanding of upper-air circulation in the years since the Norwegian cyclone model.

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