symmetry [struc petrol] . The symmetry of a fabric is the combined symmetry of all the elements making up the fabric. There are five possible symmetries: (1) spherical, for fabrics having the symmetry of a sphere; (2) axial, for fabrics having the symmetry of a spheroid; (3) orthorhombic, for fabrics having the symmetry of a triaxial ellipsoid; (4) monoclinic, for fabrics having only one unique plane of symmetry; and (5) triclinic, for fabrics having no planes of symmetry (Turner and Weiss, 1963, p.43-44).
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.
channel flow . Movement of surface runoff in a long narrow troughlike depression bounded by banks or valley walls that slope toward the channel; specif. streamflow. Cf: overland flow. Syn: concentrated flow.
summit level [geomorph] . The elevation of a summit plane. See also: accordant summit level.
metavivianite (met-a-viv'-i-an-ite''). A green platy triclinic mineral: Fe2+3-xFe3+x(PO4)2(OH)x•8-xH2O . It is a dimorph of vivianite.
unit cell . The smallest volume or parallelepiped within the three-dimensional repetitive pattern of a crystal that contains a complete sample of the atomic or molecular groups that compose this pattern, and that displays the symmetry present in the crystal structure. Crystal structure can be described in terms of the translatory repetition of this unit in space in accordance with one of the space lattices. Cf: primitive unit cell; conventional unit cell; reduced unit cell.
low quartz . Low-temperature quartz; specif. alpha quartz.
swell [struc geol] . A general, imprecise term and less-preferred syn. for dome and arch.
convective fractionation . Magmatic crystallization in which convective flow, driven by heat within the magma chamber, feeds crystallization along the floor, walls, and roof of the chamber.
regenerated rock . A clastic rock. The term "regenerirte Gesteine" was used by Zirkel (1866, p.3).
rostral suture . That portion of the facial suture of a trilobite along the join of the anterior of the rostral plate and the cranidium.
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