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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three-dimensional survey . A survey involving collecting data over an area with the objective of determining spatial relations in three dimensions, as opposed to determining components along separated survey lines. The data from such a survey constitute a volume which can be displayed in different ways. Abbrev: 3-D. See also: time slice; horizon slice; fault slice; arbitrary line; attribute [seis].

hauckite (hauck'-ite). A light yellow to orange hexagonal mineral: (Mg,Mn2+)24Zn18Fe3+3(SO4)4(CO3)2(OH)81 .

equilibrated chondrite . A chondrite whose major mineral constituents (chondrules, matrix, and metal) have equilibrated during thermal metamorphism. These meteorites are of petrographic (petrologic) grade 4, 5, 6, or 7.

seston (ses'-ton). Suspended, nonsinking particulate material in ocean or lake water. It consists of living and dead algae, particulate organic matter, and mineral particles.

lophophytous (loph-o-phyt'-ous). Said of a sponge that is fastened to the substrate by a tuft of spicules.

vermilion (ver-mil'-ion). (a) cinnabar. (b) An orange-red garnet; vermeil. Syn: vermillion.

Marsden square . One of a system of numbered areas each 10 degrees latitude by 10 degrees longitude, based on the Mercator projection, and used chiefly for identifying geographic positions and showing distribution of worldwide oceanographic and meteorologic data on a chart. Each square is subdivided into 100 one-degree subsquares which are numbered from 00 to 99 starting with 00 nearest the intersection of the equator and the Greenwich meridian. The system was introduced in 1831 by William Marsden (1754-1836), Irish orientalist.

phosphatization (phos''-pha-ti-za'-tion). Conversion to a phosphate or phosphates; e.g. the diagenetic replacement of limestone, mudstone, or shale by phosphate-bearing solutions, producing phosphates of calcium, aluminum, or iron. Cf: phosphorization.

isochore [stratig] . A line drawn on a map through points of equal drilled thickness for a specified subsurface unit. Thickness figures are uncorrected for dip in vertical wells, and corrected for hole angle, but not for dip, in deviated wells. Cf: isopach.

Lemuria (Le-mu'-ri-a). An imaginary continent, also known as Amosnuria, beloved by science-fiction writers, that is alleged to have occupied most of the central Pacific Ocean until historic time, when it sank, leaving only the Pacific islands as tiny remnants. The dispersal of Polynesian peoples and cultures is supposed to have been facilitated by the existence of Lemuria, but this dispersal is easily explained otherwise. Geologically, the existence of such a continent, either modern or ancient, is impossible.

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