Fold, fault and joint; attitude

Fold

A fold is a bend or wavy curvature in originally flat rock layers (beds), produced by compressive stress acting on rocks that behave plastically over a long time.

   anticline        syncline
     ___          \       /
   /     \          \___/

Fault

A fault is a fracture in the rock mass along which the two blocks have moved relative to each other, parallel to the fracture surface. The displacement may range from a few millimetres to hundreds of kilometres. A fault has a fault plane, a hanging wall and a foot wall; its types are normal, reverse and strike-slip.

Joint

A joint is a fracture along which there is no appreciable displacement. Joints occur in sets and systems and may be tension, shear or cooling joints.

Attitude

The attitude of a geological structure is its orientation in space, expressed by the strike (direction of the horizontal line on the plane) and the dip (maximum inclination, at 90° to the strike, given as dip direction and dip amount). For lines the attitude is the trend and plunge. Example: N30°E / 40° SE.