drift correction . Adjustment to remove the effects of geophysical drift, usually by repeated observations at a base station.
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.
orthochlorite (or-tho-chlo'-rite). (a) A group name for distinctly crystalline forms of chlorite (such as clinochlore and penninite). (b) A group name for chlorites conforming to the general formula: (M2+,M3+)6(OH)8[(Si,Al)4O10]. (Hey, 1962, p.546). Cf: leptochlorite.
debris ice . (a) Sea ice containing soil, mud, stones, shells, and other material. (b) brash ice.
Fermat's principle (Fer'-mat's). The statement that a seismic wave will follow the path between two points that takes less time than variations of this path. Such a path is called a minimum-time path. Occasionally involves a maximum-time path, as with reversed branches, or an inflection point.
level [surv] . n. (a) A leveling instrument. (b) A device or attachment for finding a horizontal line or plane or for adjusting an instrument to the horizontal; specif. a spirit level. (c) A measurement of the difference of altitude of two points on the Earth's surface by means of a level. v. To find the heights of different points by means of a level.
luhite (lu'-hite). A calcite-rich dike rock with olivine and titanian augite in a groundmass of clinopyroxene, melilite, hauyne, nepheline, and calcite; a hauyne-melilite damkjernite or hauyne-nepheline alnoite. The rock was named by Scheumann in 1913 for Luh, Czech Republic. Obsolete.
beaked apex . The upper angle of tergum of a cirripede crustacean, produced into a long narrow point (TIP, 1969, pt. R, p.91).
Santernian (San-ter'-ni-an). An Italian substage: lower substage of regional Calabrian stage, lowermost Pleistocene (below Emilian substage).
micrinite (mic'-ri-nite). A maceral of coal within the inertinite group having a reflectance higher than that of associated vitrinite, without recognizable plant-cell structure, and occurring as discrete particles of size less than 2 micrometers, commonly about 1 micrometer. Cf: macrinite; residuum [coal].
space-frequency domain . The two-dimensional transform of a seismic section from location versus time to wave-number versus frequency.
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