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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entropy map . A facies map that is based on the degree of "mixing" of three end members (rock components) of a given stratigraphic unit, but that does not distinguish the natures of these end members (see Forgotson, 1960; Krumbein and Sloss, 1963). Cf: entropy-ratio map.

resolution [speleo] . The solution of speleothems that come into contact with undersaturated water, often during flooding; sometimes called "redissolving".

radiation [surv] . A method of surveying in which points are located by a knowledge of their distances and directions from a central point.

antiphase boundary . The boundary between antiphase domains. Abbrev: APB.

serpent stone . A stone, usually a highly absorbent aluminous gem, once believed to be formed by snakes and to be efficacious in drawing out poison; specif. adder stone.

longicone (lon'-gi-cone). A long, slender, conical, gradually tapering shell characteristic of certain orthoconic cephalopods. Also, a fossil animal having such a shell. Cf: brevicone.

condensation zone . A concentration of several biozones in a single bed (Heim, 1934).

birefringent (bi-re-frin'-gent). Said of a crystal that displays birefringence; such a crystal has more than one index of refraction. Syn: birefractive; birefracting.

littoral drift . Material (such as shingle, gravel, sand, and shell fragments) that is moved along the shore by a littoral current. Syn: longshore drift; shore drift.

celestial longitude . Angular distance east of the vernal equinox, along the ecliptic, between the circle of latitude of the vernal equinox and the circle of latitude of a point on the celestial sphere; measured eastward from the circle of latitude of the vernal equinox, through 360°. Cf: longitude. Syn: ecliptic longitude.


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