Fold terminology i
Fold terminology in two dimensions
Looking at a fold surface in profile the fold can be divided into hinge and limb portions. The limbs are the flanks of the fold and the hinge is where the flanks join together. The hinge point is the point of minimum radius of curvature for a fold. Thecrest of the fold is the highest point of the fold surface, and the trough is the lowest point. The inflection point of a fold is the point on a limb at which the concavity reverses, on regular folds this is the mid-point of the limb.