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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GeoWord of the Dayaxial-plane cleavage . Cleavage that is, in the hinge of a fold, parallel to the hinge surface of the fold and whose intersection lineation with bedding is parallel to the fold hinge. Axial-plane cleavage may be everywhere parallel to the fold hinge surface, but normally cleavage fans or changes its orientation systematically with position about the fold. Cf: bedding-plane cleavage; fan cleavage; transecting cleavage.

GeoWord of the Dayvolcanic accident . A departure from the normal cycle of erosion, caused by the outbreak of volcanic activity. See also: accident; climatic accident.

GeoWord of the Daygaseous transfer (gas'-e-ous). Separation from a magma of a gaseous phase that moves relative to the magma and releases dissolved substances, usually in the upper levels of the magma, when it enters an area of reduced pressure. See also: pneumatolytic differentiation.

GeoWord of the Dayplanèze (pla-neze'). An erosional relief form consisting of a lava flow protecting the underlying volcanic cone. It may be a wedge-shaped unit on the slope of an erosionally dissected volcano, or a lava-capped plateau. Etymol: French, "lava plateau". Also spelled: planeze.

GeoWord of the DayAlford rotation . Rotating the information from orthogonal horizontal geophones into the natural coordinate system. Used in S-wave studies, especially birefringence studies.

GeoWord of the Dayforeland [geog] . The land lying in front of or adjoining other land and physiographically related to it.

GeoWord of the Daydiaene (di'-aene). A sponge spicule with two rays of equal length and one of a different length, usually longer; a triaene with one ray reduced or absent.

GeoWord of the DayKeuper (Keu'-per). A term used (esp. in Germany) to what is now approx. the Upper Triassic (above Muschelkalk, below Jurassic). Essentially a lithostratigraphic term.

GeoWord of the Daycryosol . Soil formed in either mineral or organic materials having permafrost either within 1 m below the surface or, if the soil is strongly cryoturbated, within 2 m below the surface, and having a mean annual ground temperature below 0° C. Cryosols are divided into turbic cryosols developed on mineral soils and strongly cryoturbated; static cryosols developed on mineral soils but with little or no cryoturbation; and organic cryosols developed on organic (peat) materials (Canada Soil Survey Committee, 1978).

GeoWord of the Daymottles . Spots or blotches of different color or shades of color interspersed with the dominant color. See also: mottled zone; soil color.