Summary
The topics covered in this chapter can be summarized as follows:
| Section | Summary |
|---|---|
| 10.1 Stress and Strain | Stress within rocks—which includes compression, extension and shearing—typically originates from plate-boundary processes. Rock that is stressed responds with either elastic or plastic strain, and may eventually break. The way a rock responds to stress depends on its composition and structure, the rate at which strain is applied, and also to the temperature of the rock body and the presence of water. |
| 10.2 Folding | Folding is generally a plastic response to compressive stress, although some brittle behaviour can happen during folding. An upward fold is an antiform. A downward fold is a synform. The axis of a fold can be vertical, inclined, or even horizontal. If we know that the folded beds have not been overturned, then we can use the more specific terms: anticline and syncline. |
| 10.3 Faulting | Fractures (joints) typically form during extension, but can also form during compression. Faulting, which involves the displacement of rock, can take place during compression or extension, as well as during shearing at transform boundaries. Thrust faulting is a special form of reverse faulting. |
| Lab 10 Exercises | Block models are useful tools for examining and recognizing geologic structures in 3D. Writing a geologic history for the units shown on a block model is an excellent way to practice using the principles of stratigraphy to determine relative ages. |