Chapter 11: Rock Deformation Chapter 11 Rock Deformation or what you always wanted to know abou folds, faults, and joints MIDTERM- NOVEMBER 14 Stress= the force applied to a plane divided by the BRING A SOFT PENCILA area of the plane. compressive tensile shear FINAL EXAM DEC.17,12:00 GOLD GYM Rock Deformation Rock Deformation The propagation of seismic through rocks is an elas- response, since the rocks return to their original shape. The change in volume or shape of an object that results from stress is called strain Ductile(plastic) response of rock layers results in folds permanent wavelike deformations in layered rocks The response of rocks to stress can be divided into Brittle response to stress results in faults= a fracture in elastic response: rock returns to original shape bedrock along which rocks on one side have moved relative ductile or plastic response: permanent deformation to the other side. Where such movement is absent. the without fracture occurs above the fracture is called a joint (several joints= joint sets SO-called elastic limit brittle response: fracturing of a rock with little deformation The rock response to stress is influenced by a number of prior to its rupture factors: type of stress, type of rock, temperature, pressure, nuids, length and magnitude of stress applied Rock Deformation Orientation of planar features in space The direetion of the line formed by the intersection of a Fig.11.6 horizontal plane with a bedding/fault plane is called strike. The angle formed by the intersection of a bedding/fault plane and the horizontal plane measured in a vertical plane perpendicular to the strike is called dip. The symbol used by geologist to display strike and dip on a map is the following1 Chapter 11 Rock Deformation MIDTERM ñ NOVEMBER 14 ñ BRING A SOFT PENCIL! FINAL EXAM DEC. 17, 12:00 GOLD GYM Chapter 11: Rock Deformation or what you always wanted to know about folds, faults, and joints Stress = the force applied to a plane divided by the area of the plane. lithostatic compressive tensile shear stress applied equally forces directed toward one another forces directed away from one another stress that acts parallel to a plane Rock Deformation The change in volume or shape of an object that results from stress is called strain. The response of rocks to stress can be divided into - elastic response: rock returns to original shape - ductile or plastic response: permanent deformation without fracture; occurs above the so-called elastic limit - brittle response: fracturing of a rock with little deformation prior to its rupture Rock Deformation The propagation of seismic waves through rocks is an elas￾tic response, since the rocks return to their original shape. Ductile (plastic) response of rock layers results in folds = permanent wavelike deformations in layered rocks Brittle response to stress results in faults = a fracture in bedrock along which rocks on one side have moved relative to the other side. Where such movement is absent, the fracture is called a joint (several joints = joint sets) The rock response to stress is influenced by a number of factors: type of stress, type of rock, temperature, pressure, fluids, length and magnitude of stress applied. Rock Deformation The direction of the line formed by the intersection of a horizontal plane with a bedding/fault plane is called strike. The angle formed by the intersection of a bedding/fault plane and the horizontal plane measured in a vertical plane perpendicular to the strike is called dip. The symbol used by geologist to display strike and dip on a map is the following: 45 Fig. 11.6 Orientation of planar features in space