CREST, POINT, LINE, PLANE
In a fold profile, the point of highest elevation on a surface is
called is called CREST or CRESTAL POINT and the one of lowest the TROUGH
or TROUGH point. The hinge point and crestal point may coincide in a fold
whose axial plane is vertical. A line joining the highest points on a
single surface is called the CRESTAL LINE. There could be an equivalent TROUGH LINE as well. On a folded surface
in a fold profile, the point of least curvature is called the INFLEXION
POINT. A line joining such points on a folded surface is called INFLEXION
LINE. A plane containing crestal lines on a single folded surface is
called an ENVELOPING SURFACE which may be planar or curviplanar. Similar
plane containing trough lines is also called an enveloping surface. A
plane containing all inflexion lines in a single folded surface is called
the MEDIAN PLANE or surface. |