In situ experimental study of roughness development at a stressed solid/fluid interface
Bas Den Brok, Jacques Morel, Mohsine Zahid, 2002. "In situ experimental study of roughness development at a stressed solid/fluid interface", Deformation Mechanisms, Rheology and Tectonics: Current Status and Future Perspectives, S. de Meer, M. R. Drury, J. H. P. de Bresser, G. M. Pennock
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Theory and experiments have demonstrated that the initially flat surface of an elastically strained solid is morphologically unstable. The elastic strain energy of a rough, corrugated surface is lower than that of a flat one. Hence, stress forces the surface into a rough structure, but the associated increase in surface energy counteracts this roughening. In this way an equilibrium surface roughness consisting of μm-scale grooves and ridges can develop if the solid is transported, e.g. by diffusion through an aqueous solution, from sites of high stress to sites of low stress. We report in situ experimental observations of the surface of elastically strained potassium (K-) alum single crystals held in K-alum solution. The observations confirm earlier reports of the development of stress-induced μm-scale grooves on the surface of this material. The in situ observations show, however, that the stress-induced surface morphology is not a static, but a dynamic structure. The grooves are mobile, and may for example propagate or increase or decrease in length. They may move upwards, downwards, or remain where they are. Others rotate and undulate. It is suggested that if stress is high enough, grain boundaries in (wet) rocks could posses a similar structure of channels, continuously changing position and orientation, in line with the so-called ‘dynamically stable’ island-channel grain boundary structure that is essential to several pressure solution models.
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The motion and deformation of rocks are processes of fundamental importance in shaping the Earth, from outer crustal layers to the deep mantle. Reconstructions of the evolution of the Earth therefore require detailed knowledge of the geometry of deformation structures and their relative timing, of the motions leading to deformation structures and of the mechanisms governing these motions. This volume contains a collection of 22 papers on field, experimental and theoretical studies that add to our knowledge of these processes. They are a mixture of review papers oh selected topics in the field of structural geology and tectonics and papers on current issues and new techniques and are grouped into four themes:
The effect of fluids on deformation
The interpretation of microstructures and textures
Deformation mechanisms and rheology of crust and upper mantle minerals
Crust and lithosphere tectonics
The volume will appeal to researchers in the fields of structural geology and tectonophysics, both in academia and industry.