Mechanics of folding 15 what is the difference

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Mechanics of Folding 15. What is the difference between “passive” and “active” folding? – Active folding is folding controlled by the stiff layers in strata; passive folding is not controlled by layers and may shear. What is the role of mechanical anisotropy? -What kind of folding is flexural folding? - Active 16. What is the distinction between bending and buckling? – In bending the applied force is oriented at an oblique angle to layering, in buckling- the force is oriented parallel to the mechanical anisotropy 17. In the buckling experiments of Fig 10.29, what is the only variable that changes?- thickness of layer What is the effect of that change?- fold differently depending on thickness of layer 18. Explain how it is possible to estimate viscosity ratios in folded rocks.- 19. In Fig 10.31, what happens to the fold as the viscosity ratio approaches 1 (no viscosity contrast)?
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20. How far apart do two layers have to be before they interfere with each other during folding (see sec 10.7.3)- thick layers = big wavelength, thin layers= short wavelength Kinematic Models 21. What is the difference between flexural slip and flexural flow folds? – flexural folds have concentric geometry and similar folds, flexural slip are characterized by diverging isogons (concentric geometry) and shear strain (slip) between the layers. 22. How does neutral surface folding differ from flexural slip folds-it has extension in outer arc and shortening in inner arc and has neutral surface where nothing occurs, outer arc can have normal faults and boudins, inner arc can have thrust faults Shear folding- shearing occurs across the layering rather than boundaries, common in shear zones Fold flattening- similar folds can be produced from concentric folds (class I) by continuing to shorten to the buckling stage
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  • Fall '08
  • Staff
  • Geology, Thrust fault, Cylindrical fold fold, noncylindrical fold Fold, Noncyldrical fold- folds

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