Earth Sciences 1022A/B Chapter Notes - Chapter 8: Convergent Boundary, Differential Stress, Gypsum

• School: Western University
• Department: Earth Sciences
• Course: Earth Sciences 1022A/B
• Professor: Hitchcock

Document Summary

Large tectonic forces deform the crustal rocks and create mountains, shift islands, and move rocks. General term that refers to all changes in the orientation and location of a rock. Occurs next to plate margins where segments of lithosphere move relative to one another and generate tectonic forces. Rocks deform when subjected to stress (force applied in a given area) Strain is the visible result of stress. Shortens and thickens crust by folding and breaking/faulting rocks. Differential stress that forces rocks to move past other rocks. Manifested differently between shallow, near surface rocks and rocks at deeper depths. Shallow: closely spaced parallel surfaces and bedding planes. Deep: deformed by solid-state flow (plastic behaviour) Rocks deform when subjected to stress that exceed their own strength. Rock type and rheology (rock strength ) has a great influence on the type and degree of deformation particularly in near-surface environments. Sedimentary rocks (gypsum, halite and shale) are more susceptible to ductile flow.