Earth Sciences 1022A/B Lecture 9: Lecture 9

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

Document Summary

All changes in the original form of a rock body subjected to stress. Most deformation in earth"s crust occurs along or near margins of lithospheric plates where movement occurs. Stress the amount of force applied to a given material: two main forms, uniform stress stress applied to material equally in all directions, differential stress stress applied to material unequally. Strain the observed result of stress (as revealed by structures produced by deformation) Compressional stress (squeezing) causes rock bodies to shorten and thicken vertically. Tensional stress (stretching) causes rock bodies to lengthen and thin vertically. Shear stress (slicing motion) causes rock bodies to change shape laterally. Each of the three types of stress predominates at one of the three main plate boundaries. Convergent plate boundaries lithospheric plates move towards each other: compressional stress. Divergent plate boundaries lithospheric plates move away from one another: tensional stress. Transform plate boundaries lithospheric plates move alongside one another: shear stress.