RFG 2018 Conference

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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neptunist (nep'-tun-ist). An adherent to the theory of neptunism. Ant: plutonist.

sieve deposition . A term proposed by Hooke (1967, p.454) for the formation of coarse-grained lobate masses on an alluvial fan whose material is sufficiently coarse and permeable to permit complete infiltration of water before it reaches the toe of the fan.

frost-pattern soil . A term used by Troll (1944) for what is now known as patterned ground; it is a misleading term because patterned ground need not consist of soil, nor need it involve a periglacial origin.

junoite (ju'-no-ite). A metallic monoclinic mineral: Pb3Cu2Bi8(S,Se)16 .

run [streams] . n. (a) A small, swiftly flowing watercourse; a brook or a small creek. (b) A channel unit in which downstream channel-bed gradient, flow depth, and grain size are intermediate between those characterizing riffles and pools.

barbertonite (bar'-ber-ton-ite''). A rose-pink to violet hexagonal mineral: Mg6Cr2(CO3)(OH)16•4H2O . It is dimorphous with stichtite, and a member of the manasseite group.

rhomboid ripple . An aqueous current ripple characterized by diamond-shaped tongues of sand arranged in a reticular pattern resembling the scales of certain fish. Tongues range from 12 to 25 mm in width and 25 to 50 mm in length; each has one acute angle (formed by two steep sides) pointing downcurrent, and another acute angle (formed by the gentle side extending into the reentrant angle of the steep sides of two tongues of the following) pointing upcurrent; it is common on sand beaches where it forms during the final stages of backwash of each retreating wave. The sides are not more than 1 mm high. The term "rhomboid" applied to a ripple was introduced by Bucher (1919, p.153). Syn: rhomboid current ripple; overhanging ripple.

orthophoto quarter-quadrangle . An orthophoto quadrangle in a standard quadrangle format of 3.75 minutes of longitude by 3.75 minutes of latitude at 1:12,000 scale (USGS, 1991, p.1-1, 1-2). Abbrev: OQQ.

jordisite (jor'-dis-ite). A black amorphous mineral: MoS2 . Cf: molybdenite.

advection [ore dep] . Unidirectional mass transport of solutes by bodily movement of hydrothermal fluids through permeable rocks, commonly across boundaries between volumes with contrasting chemical properties. It is contrasted with diffusion. Advection is measured in terms of fluid velocity and concentrations of solutes.


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