Glossary

Discontinuity – In structural geology, a discontinuity is the collective term used to describe all fractures or structural features of weakness in a rock mass. The terms include bedding and schistosity planes, faults, shears, joints and lithological contacts. Discontinuities divide the rock mass giving it a discontinuous structure.

Daylights – Something that can be seen on the rock face (where discontinuities see daylight).

Geological Domain – A volume of homogeneous rock with a single grade population and orientation.

Dip – The angle that a structural surface (for example, a bedding plane, fault shear or joint) makes with the horizontal. It is used to describe the line of steepest declination in the plane of the structural surface. Its values may vary from 0 to 90 degrees.

Dip Direction – Compass bearing expressing the direction of the dip. It is measured in the horizontal plane, from north in a clockwise direction and varies between 0 to 360 degrees.

Discontinuity – The collective term used to describe all fractures or structural features of weakness in a rock mass. This includes bedding planes, schistosity planes, faults, shears, joints and lithological contacts. Discontinuities divide the rock mass giving it a discontinuous structure.

Factor of Safety – The ratio of the resisting force to the sliding force along the sliding surface of a wedge or block.

Joint – A type of discontinuity in which there has been a parting of the rock and virtually no displacement along or across the plane of parting. Often occurs with parallel joints to form part of a joint set.

Persistence – Persistence, or chord length, of a discontinuity is the areal extent or penetration length following along the discontinuity from one end to the other. Termination in solid rock or against other discontinuities reduces the persistence.

Plane/Bedding Plane – A planar or nearly planar bedding surface that visibly separates each successive layer of stratified rock of the same or different lithology. A term commonly applied to a plane of discontinuity along which a rock tends to split or break readily.

Plunge – The vertical angle a linear geological feature makes with the horizontal plane.

Orientation – The direction of a structural feature in space such as a discontinuity and usually in reference to the points of a compass. It can be defined by two measurements, such as dip and dip direction or strike and plunge.

Rock Mass – An in-situ mass of rock containing both intact rock and discontinuities that separate the rock material. Rock masses generally contain different rock types and discontinuities arranged in a variety of ways to give the rock mass a particular structure.

Scanline – A straight line that is drawn across the rockface. Any discontinuity that crosses the scanline is selected and analysed as part of that scanline set.

Survey Point – Used to calculate the Easting, Northing and Height of a point.

Survey Line – Used to calculate the length of the line you map on the 3D image. The line may be used as a reference line, or to measure the distance from one point to another.

Strike – The line formed by the intersection of a horizontal plane and an inclined surface. Perpendicular to the dip direction.

Terzaghi Correction – A correction applied to Spherical, Contour and Rosette Plots to account for sampling bias introduced by orientation data collection along traverses.

Trace – A linear trace mapped along a structural feature that enables the calculation of geological properties for that feature.

Trend – The trend is measured in the direction of plunge and is the geographical azimuth angle measured in a clockwise rotation from North which equals zero degrees.