Geological_Sciences_1100[1] - Chapter10CrustalDeformation...

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Chapter 10—Crustal Deformation 28/10/2010 14:31:00 Chapter 10—Crustal Deformation Structural Geology:  A Study of Earth’s Architecture Used for deciphering Earth history and economic well being (like finding oil,  natural gas, etc.  like what Daddy does) Rock fracture are sites of hydrothermal mineralization—sites of mineral ore  deposits Orientation of fractures must be considered when building Deformation Deformation—all changes in the size, shape, orientation, or position of a rock  mass Usually occurs along plate margins o Plate motions and the interactions along plate boundaries generate the  tectonic forces that cause rock units to deform Force and Stress     Force—that which tends to put stationary objects in motion or change the  motion of moving bodies Stress—the amount of force applied to a given area o Magnitude of stress depends on amount of force applied and area on  which the force acts o How concentrated the force is o Confining pressure—stress applied uniformly o Differential stress—Nonuniformly  Types of Stress     Differential stress
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o Compressional—shortens a rock body Floding, flowing, and faulting More concentrated when mineral grains are intact, grains  shorten in the direction parallel to the place of maximum stress o Tensional stress Elongate or pull apart Divergent plate boundaries Lengthen  o Shear Like pushing on the side of a deck of cards, slides along while  bottom remains stationary Occurs on closely spaced parallel surfaces of weakness  (bedding, foliation, microfaults) Strain     Irreversible change in the shape and size of a rock body Do not retain their original configuration during deformation How Rocks Deform     Occurs when rocks are subjected to stresses greater than their own strength Usually folding, flowing or fracturing Elastic deformation—recoverable changes in rock form, rock will eventually  return to original form Once the elastic limit of a rock is surpassed it either flows (ductile  deformation) or fractures (brittle deformation) Deformation influencing fractures o Rock type o Temperature
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This note was uploaded on 09/14/2011 for the course GEO 1010 taught by Professor Rogers during the Spring '11 term at Missouri (Mizzou).

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Geological_Sciences_1100[1] - Chapter10CrustalDeformation...

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