Reference work entry
A fold is a deformed geologic surface caused by bending or curving of strata. The most common type is folds formed by layered sedimentary rocks. A fold is composed of a fold centre, two limbs and a crest. A fold can be illustrated by the ‘fold elements’, such as the axial plane, axis, hinge point, crest plane, crest line, trough surface, trough line, axial trace, saddle, crest, inflection point, plunge, tilt, fold wavelength, fold amplitude, and fold envelope surface. Folding of rocks results in a variety of scenery; in particular, many mountain systems are the result of intense folding of rocks, which forms spectacular landscapes (Fig. 12).
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