The origin of folding in the Earth's crust

Abstract

In the light of recent special study, folding phenomena represent the reaction of the layered beds of the earth's crust on the differential vertical movements of separate blocks of the crust. It is possible to distinguish the following types of folding. Block folding represents the most direct reaction of layers on the vertical movements of the crust's blocks, the most characteristic of this type of folding being boxlike folds. They occur both on platforms and in geosynclines. Injection folding is due to the horizontal flow of the more plastic rocks, which are squeezed out from some areas and accumulate in others, where injection or piercement cores are formed. The flow of plastic rocks results from the uneven load of superimposed layers and especially from the fractures that cut these layers. The main places of occurrence of injection folding are foredeeps and tectonic basins. Metamorphic or deep folding is connected with the processes of granitization and metamorphism when the density of rocks becomes lower as the result of the impregnation of rocks by volatile substances. Reduced density induces upward flow, as a result of which deep diapirlike structures are formed. The folding of general crumpling mostly represents the influence of gravitational forces provoking the sliding of layers down the slopes or the spreading out of the upper parts of the elevated blocks. Such spreading out creates horizontal compressive forces which crumple the adjacent layers into folds. Sometimes the folding of general crumpling is created by the pushing apart under the mechanical influence of injection cores or of deep metamorphic diapirlike structures. The deep folding and the folding of general crumpling occur widely in geosynclinal belts. There are no indications in the phenomena of folding of the existence of general compressional forces in the earth's crust. Horizontal compression exists only as a local phenomenon and is limited to some narrow belts within geosynclines. The causes of horizontal compression are also local. Only vertical movements of separate blocks of the crust exist as primary phenomena.

A model for the fragmentation kinetics of crumpled thin sheets

“…Specifically, we seek a scaling solution independent of initial conditions, a property that allows us to solve analytically and proves compatible with the chosen form of homogeneous breakup kernels 27 . We thereby test a scaling ansatz c(x, t) = ϕ(ξ)/s(t) 2 as proposed in Cheng and Redner 27 , where ξ = x/s(t), and the mean area, s(t), carries all explicit dependence on t. The scaling function ϕ(ξ) satisfies R 1 0 ϕðξÞdξ ¼ 1 and…”

“…Crumpling is a complex, non-equilibrium process arising in diverse systems across a wide range of length scales, from the microscopic crumpling of graphene membranes 1 , to the macroscopic folding of Earth’s viscoelastic crust 2 . Crumpled structures are highly porous, providing function for applications such as high-performance batteries and supercapacitors by increasing the electrochemical surface area 3 , 4 .…”

Simulation of crumpled sheets via alternating quasistatic and dynamic representations

“…Crumpled structures are often considered a model complex system in soft matter. Crumpling is found both in nature, from geological deformations [1] to the packing of genetic material [2,3], and in scientific applications: Crumpled graphene, for instance, has been used to develop high-performance biosensors [4] and electrodes for batteries and supercapacitors [5,6,7] by leveraging the increased functional surface area of these porous structures. However, crumpling often proceeds in an unpredictable manner: As a thin sheet is confined, stresses spontaneously localize to produce a complex network of creases in the sheet [8,9].…”

A model for the fragmentation kinetics of crumpled thin sheets

“…Crumpling is a complex, non-equilibrium process arising in diverse systems across a wide range of length scales, from the microscopic crumpling of graphene membranes [1], to the macroscopic folding of Earth's viscoelastic crust [2]. Crumpled structures are highly porous, providing function for applications such as high-performance batteries and supercapacitors by increasing the electrochemical surface area [3,4].…”