Chapter 10: CRUSTAL DEFORMATION 1. Structural Geology a. Deformation a.i. Changes in shape, position, orientation of a rock a.ii. Caused by differential stress (force applied over an area) exceeding the rock strength a.iii. Flow, fold, fracture, fault a.iv. The “architecture” of the crust: folds, faults, joints, etc. formed by tectonic stresses a.iv.1. Economically important-traps for oil/gas, sites for ore deposits, construction b. 3 types of stress b.i. Confining pressure-equal stress all directions b.ii. Differential stress- non-uniform and unequal b.ii.1. Compressional- squeezes and shortens b.ii.1.a. Convergent margins b.ii.1.b. Shortening and thickening b.ii.2. Tensional-pull apart, elongates b.ii.2.a. Divergent boundaries b.ii.2.b. Shallow faulting b.ii.2.c. Deep ductile flow b.ii.3. Shear-one part slides past another like a deck of cards b.ii.3.a. Transform boundaries b.ii.3.b. Slippage on parallel surfaces b.ii.4. Strain-change in shape caused by differential stress c. Types of deformation c.i. Elastic c.i.1. Recoverable like rubber band, no breaking of chemical bonds in mineral structures c.ii. Brittle c.ii.1. Break into pieces, bonds break c.ii.2.