Lecture18

# Lecture18 -...

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Unformatted text preview: http://www.jwolfe.clara.net/Humour/NonMedPicts/Stress-FishInBlender.gif Chapter 10 Crustal Deformation Deformation ¾ Deformation is a general term that refers to all changes in original form and/or size of rock body ¾ Most crustal deformation occurs along plate margins ¾ Deformation involves • Force – that which tends to put stationary objects in motion or changes the motions of moving objects • Force = (mass x acceleration) • Stress - force applied to a given area in a solid • Stress = (force / surface area) • Pressure - force applied to a given area in a fluid Mass acceleration 0.5in 2 1in 2 0.5in 2 1in 2 force force force force 1in 2 1in 2 1in 2 1in 2 force force force force ¾ Types of stress • Compressional stress – shortens a rock body • Tensional stress – tends to elongate or pull apart a rock unit • Shear stress – produces a motion similar to cards sliding past each other when pushed from the side Figure 10.2 ¾ Strain – changes in the shape or size of a rock body caused by stress ¾ How rocks deform • Rocks subjected to stresses greater than their own strength begin to deform usually by folding, flowing, or fracturing • General characteristics of rock deformation • Elastic deformation – the rock returns to nearly its original size and shape when the stress is removed. fractures http://www.learner.org/jnorth/images/graphics/m/Muscle_RubberBand1.jpg http://www.learner.org/jnorth/images/graphics/m/Muscle_RubberBand2.jpg Elastic deformation of a rubber band. Band will return to original size after the stress is removed. ¾ Strain – changes in the shape or size of a rock body caused by stress ¾ How rocks deform • Rocks subjected to stresses greater than their own strength begin to deform usually by folding,...
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## This note was uploaded on 04/18/2011 for the course EAS 101 taught by Professor Kirschner during the Spring '11 term at Saint Louis.

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Lecture18 -...

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