Term used in Structural Geology


A flat surface; it has the property that a line joining any two points lies wholly on its surface. Two intersecting lines define a plane. 


The general term for the orientation of a plane or line in space, usually related to geographical coordinates and the horizontal. Both trend and inclination are components of attitude. 


The direction of a horizontal line specified by its bearing or azimuth. Bearing: the horizontal angle measured east or west from true north or south. 


The horizontal angle measured clockwise from true north. 


The trend of a horizontal line on an inclined plane. It is marked by the line of intersection with a horizontal plane. 

Structural bearing

The horizontal angle measured from the strike direction to the line of interest. 


The vertical angle, usually measured downward, from the horizontal to a sloping plane or line. 

True dip

The inclination of the steepest line on a plane; it is measured perpendicular to the strike direction.

Apparent dip

The inclination of an oblique line on a plane; it is always less than true dip.