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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time-domain electromagnetic method (time'-do-main). Transmission of a single or repetitive pulse of electromagnetic energy, frequently of square wave form, and reception of electromagnetic energy, as a function of time, in the time interval after the transmitted wave form has been turned off. It is used with induced electrical polarization and electromagnetic methods. Abbrev: TDEM. Syn: transient electromagnetic method.

gibber plain . A desert plain strewn with wind-abraded pebbles, or gibbers; a gravelly desert in Australia.

field well . A well drilled for oil or gas within the area of a pool that has already been essentially proved for production (Lahee, 1962, p.132-133).

dolocast (do'-lo-cast). A cast or impression of a dolomite crystal, preserved in an insoluble residue. Rarely used. Adj: dolocastic. Cf: dolomold.

konderite (kon'-de-rite). A metallic gray hexagonal mineral closely related to inaglyite: PbCu3(Rh,Pt,Ir)8S16 .

megaclone (meg'-a-clone). A large, smooth monaxonic desma (of a sponge), having branches that bear cuplike articular facets, mostly terminal.

pseudoboléite (pseu-do-bo'-lé-ite). A blue tetragonal mineral: Pb31Cu24Cl62(OH)48 . Also spelled: pseudoboleite.

tectono-eustasy (tec'-ton-o-eu'-sta-sy). Worldwide change of sea level produced by a change in the capacity of the ocean basins owing to plate tectonic motions, e.g. sea-floor spreading, subduction. Term introduced by Fairbridge (1961, p.111). Cf: glacio-eustasy; sedimento-eustasy. Syn: diastrophic eustatism; tectono-eustatism.

blue hole . (a) A subsurface void developed in carbonate banks and islands, also offshore. It is open to the Earth's surface; contains tidally influenced waters of fresh, marine, or mixed chemistry; extends below sea level for the majority of its depth; and may provide access to cave passages (Mylroie et al., 1995). Cf: inland blue hole; ocean hole. (b) An obsolete term for a resurgence.

deglaciation (de''-gla-ci-a'-tion). The uncovering of a land area from beneath a glacier or ice sheet by the withdrawal of ice due to shrinkage by melting or calving of icebergs. As used in Great Britain, the term is restricted to a process that occurred in the past, in contrast to deglacierization. Also, the result of deglaciation.