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plaiting

A texture seen in some schists that results from the intersection of
relict bedding planes with well developed cleavage planes. AGI

plan

a. A map showing features--such as mine workings, geological structures,
and outside improvements--on a horizontal plane.
See also:colliery plan
b. A scheme or project for mine development. See also:planning
Nelson
c. The system on which a colliery is worked, such as longwall,
room-and-pillar, etc. Zern

planar

Lying or arranged as a plane or in planes, usually implying more or less
parallelism, as in bedding or cleavage. It is a two-dimensional
arrangement, in contrast to the one-dimensional linear arrangement.
AGI

planar cross-bedding

a. Cross-bedding in which the lower bounding surfaces are planar surfaces
of erosion. It results from beveling and subsequent deposition.
AGI
b. Cross-bedding characterized by planar foreset beds. AGI

planar element

A fabric element having two dimensions that are much greater than the
third; e.g., bedding, cleavage, and schistosity. CF:linear element
AGI

planar flow structure

See:platy flow structure

planar gliding

Uniform slippage along plane surfaces. AGI

planar structure

See:platy flow structure

planation

The widening of valleys through lateral corrasion by streams after they
reach grade and begin to meander and form floodplains. Also, by the
extension, the reduction of divides and the merging of valley plains to
form a peneplain; peneplanation.

plane

a. Any roadway, generally inclined but not necessarily so, along which ore
or workers are conveyed by mechanical means from one bed to another or to
a lower elevation in the same bed. See also:bedding plane; fault plane;
slope. Nelson
b. A road on the natural floor of a seam. Mason
c. A two-dimensional form that is without curvature; ideally, a perfectly
flat or smooth surface. In geology the term is applied to such features as
a bedding plane or a planation surface. Adj: planar. See also:surface
AGI
d. In crystallography, a plane of symmetry dividing a crystal structure
into two mirror images. See also:symbols of crystal faces
e. A level surface bounded by straight lines, such as the faces of
crystals. Gordon

plane course

Scot. In the direction facing the joint planes. Syn:on plane

plane engineer

See:slope engineer

plane fault

A fault with a surface that is planar rather than curved.

plane figure

A plane surface bounded either by straight lines or curved lines or by a
combination of straight and curved lines. Jones, 2

plane group

The 17 possible combinations of symmetry elements which may coexist in 2
dimensions. CF:space group

plane man

See:incline man

plane of saturation

See:water table

plane of stretching

A low-angle gravity (normal) fault resulting from stretching of the
solidified top of an igneous intrusion.

plane of symmetry

Any plane which divides a crystal, crystal structure, or crystal symmetry
such that each side is a mirror reflection of the other. Represented as m
or 2 and graphically as a solid or heavy line. Syn:mirror plane

plane or rectangular coordinate

Either of two perpendicular distances of a point from a pair of
rectangular coordinate axes. Seelye, 2

plane-polarized light

Light with its electric vector confined to a plane.