Explain the different results of stress on layers of rock. Include a discussion of whether each result happens slowly or quickly.
Answers
Answer:
Rocks deforming plastically under compressive stresses crumple into folds (figure 5). They do not return to their original shape. If the rocks experience more stress, they may undergo more folding or even fracture.
Explanation: We start our discussion with a brief review of the concepts of stress and strain. Recall that stress is a force acting on a material that produces a strain. Stress is a force applied over an area and therefore has units of Force/area (like lb/in 2 ). Pressure is a stress where the forces act equally from all directions.
If stress is not equal from all directions then we say that the stress is a differential stress. Three kinds of differential stress occur.
- Tensional stress (or extensional stress), which stretches rock;
- Compressional stress, which squeezes rock; and
- Shear stress, which result in slippage and translation.
When rocks deform they are said to strain. A strain is a change in size, shape, or volume of a material. We here modify that definition somewhat to say that a strain also includes any kind of movement of the material, including translation and tilting