If you've studied how to describe folds you can now get involved in more complex ideas. Folds needed sit upright but can have various orientations. They can be symmetric or asymmetric about their axial surfaces. Their hinge lines can be straight (like wrapping a cloth around a broom handle) or be curved along their length. Folds can be considered as wave-forms and so can be harmonic or disharmonic through a sequence of layers - click here to find out more. In many rock sequences folds form on different scales. The smaller ones are described as being parasitic upon the backs of larger ones.
