The material are buried under very heavy rocks so it is very important topic to discuss the effect of this heavy weight on the internal molecular structure.
What is the change in orientation of molecules under the influence of overloading under very heavy rocks.
Dear Arvind: your question is way too ambiguous. Which kind of material is buried and under which type of rocks? Is it a landslide, a dam, or what? We geologists and petrologists deal with rocks buried under kilometers of other rocks, inside the Earth's crust. Since the load your speaking about it doesn't seem to be a "geological" burial load, but something in the order of meters or decameters (am I wrong?), and surely the behaviour of the buried material depends on which material is involved, you should be more specific, so someone in this page, with more technical knowledge, such as a civil engineer, could answer your question. Regards, Sebastián Grande.
At extremely high pressures in depths of the so-called ultra-high-pressure metamorphosis, for example, the tetragonal mineral quartz (SiO2) is transformed into the monoclinic high-pressure modification coesite. The high pressure conditions are only reached during subduction of continental crust at depths of more than 100 km. Similarly, the element carbon (C) in the form of the mineral graphite transforms into the mineral diamond at great depths and at extremely high pressures. The high-pressure modifications are significantly heavier than the low pressure modifications and the crystal system changes, which means that the molecules are compressed in a confined space and the lattice constants are short. In the case of pure carbon, the graphite crystallizes in the hexagonal system and its high pressure modification diamond crystallizes in the cubic system with the densest sphere packing possible.
Best regards,
Guenter Grundmann
Dear Arvind,
As said by Sebastián, changes in rocks depend on the rocks involved in deformation and the degree of deformation. The initial deformation is brittle, without change in crystal lattice and orientation. The next step is creep, where pressure solutions play major role. There you have recrystallization (and hence partial reorientation of molecules) of the most sensitive minerals (e.g. quartz) perpendicular to the main stress, obtaining elongated shape with contemporaneous (passive) mechanical reorientation of grains, which lead to development of preferred orientation. Mylonitization can be considered as an extreme process of this kind, where majority of the minerals involved recrystallize in more or less common orientation. Finally, as said by Guenter, in extremelly high pressures (and high temperatures) all constituents recrystalize, tending to obtain as equidimensional as possible shape, to be stable at very high to ultra-high pressures.
Best regards, Mirka
- Badges
- Science topic
- Similar topics
- Engineering
- Electrical Engineering
- Electrodes