11_Rock Deformation

11_Rock Deformation - dip angle plane is inclined relative...

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Lecture 11 Rock Deformation Stress and Strain -The force applied to some body is the stress. -The changes to that body are the strain that is recorded. 2 kinds of stress: Uniform and differential stress Types of differential stress: 1. Tensional 2. Compressional 3. Shear Types of materials: Ductile – undergo plastic deformation- manifested as folds Brittle – undergo fracturing – manifested as joints or faults Parts of a Fold Axis – line drawn along points of maximum curvature Axial plane - imaginary surface that divides a fold as symmetrically as possible Limb – 2 sides of a fold Plunge – inclination of fold axis Types of folds: Symmetrical Syncline - Formed by downfolding - youngest rock is found at the center Anticline - Formed by upfolding - oldest rock is found at the center Assymetrical Overturned Recumbent Other landforms: Domes Basins strike: intersection of plane with imaginary horizontal plane
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Unformatted text preview: dip: angle plane is inclined relative to horizontal Brittle Materials and Failure Rocks under surface conditions also deform plastically but once elastic limit is exceeded, the rocks will behave like a brittle solid and fracture (joints and faults) Parts of a fault-hanging wall-footwall Types of faults A. Dip-slip faults 1. normal fault 2. reverse fault (thrust fault) B. strike- slip fault 1. right lateral 2. left lateral C. oblique –slip Fault zones Importance of studying structural geology 1. structures are conduits for fluids (water, gas, oil) and control subsurface fluid transport(petroleum exploration; hydrology) 2. active faults are where earthquakes occur(natural hazards and risk analysis) 3. faults and veins are sites of ore deposits (mineral exploration) 4. structures create zones of weakness in rocks(buildings and infrastructure)...
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This note was uploaded on 11/20/2010 for the course LIR 30 taught by Professor Thornley,k during the Spring '08 term at Santa Rosa.

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