I expect to set 4-5 assignments in this course. Some of the material in Turcotte and Schubert goes beyond the present course. The text by Turcotte and Schubert also gives an abbreviated introduction, and applies continuum mechanics to real Earth Sciences problems. I highly recommend the text by Mase as it gives a very succinct description of the basic concepts and the mathematics involved. Mase in the McGraw Hill Schaum Outline Series. We consider plastic deformation in Section 7–11.Required: course lecture notes (see below) If the applied force causing plastic deformation is removed, some fraction of the deformation remains.
Plastic deformation is a continuous, irreversible deformation without fracture. When the confining pressure on the rock approaches its brittle failure strength, it deforms plastically. As rocks are buried more deeply in the earth, they are subjected to increasingly large confining pressures due to the increasing weight of the overburden. At low temperatures and confining pressures, rocks are brittle solids, and large deviatoric stresses cause fracture. Although some metamorphic rocks with strong foliations are not strictly isotropic, the isotropic approximation is usually satisfactory for the earth's crust and mantle.Īt high stress levels, or at temperatures that are a significant fraction of the rock solidus, deviations from elastic behavior occur.
The equations of linear elasticity are greatly simplified if the material is isotropic, that is, if its elastic properties are independent of direction. In addition, the elastic strain of many rocks is linearly proportional to the applied stress. Almost all solid materials, including essentially all rocks at relatively low temperatures and pressures, behave elastically when the applied forces are not too large. Elastic materials deform when a force is applied and return to their original shape when the force is removed. For many solids it is appropriate to relate stress to strain through the laws of elasticity. In the previous chapter we introduced the concepts of stress and strain.
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