User:Alejandro Guevara Alday/sandbox
From Wikipedia, the free encyclopedia
Folds occur when one or a stack of planar surfaces such as: bedding, clivage or layering are bent as a result of permanent plastic and continuous deformation. Folds range in size from microscopic crinkles to mountain-sized folds, they occur singly as isolated folds and in extensive fold trains commonly as part of a fold belt in orogenic process.
Folds
Folds form under varied conditions of stress, hydrostatic pressure, pore pressure, and temperature gradient, as evidenced by their presence in unlitified sediments, the full spectrum of metamorphic rocks, and even as primary flow structures in some igneous rocks. Folds are commonly formed by shortening of existing layers parallel to the layering of rocks, but may also be formed by differential compaction, soil liquefaction triggered by seismic activity, due to the effects of a high-level igneous intrusion or diapiric intrusions, impact of meteorites, and as a result of displacement on a non-planar fault (fault bend fold), at the tip of a propagating fault (fault propagation fold).