Schematic block diagrams illustrating surface markings on joint faces.
A. Features that charactistically appear on the surface of a systematic joint.
B. Cuspate rib marks.
C. Ramp-shaped rib marks.
D. Ripple marks.
Twiss, R. J. and E. M. Moores (1992).
Structural geology. New York, W.H. Freeman and Company.
Joint initiation point can be seen in center of photograph
Joint initiation point can be seen in center of photograph.
It appears to originate from the tip of an older joint segment at
a high angle to the new surface.
Concentric "arrest" lines can be seen.
Outcrop is along the Colorado River, on road between Moab and Potash, Utah. USA.
Initiation point can be seen in lower-center of photograph
Large joint surface. initiation point is probably in lower-right of photograph.
Propagation direction is probably from right to left.
This is based on the orientation of the "plumose-like" markings on the cliff face.
Junipers at the base are about 2-4m tall.
Arches National Park, Utah. (Slide ID: 1991-06-14)
Fracture surface, with propagation towards the viewer.