Ch10_Outline - Chapter 10 Crustal Deformation Structural...

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1 Chapter 10 Crustal Deformation Structural geology Structural geologists study the architecture and processes responsible for deformation of Earth’s crust A working knowledge of rock structures is essential to our modern way of life Deformation Deformation is a general term that refers to all changes in the original form and/or size of a rock body Most crustal deformation occurs along plate margins Deformation involves Force – that which tends to put stationary objects in motion or changes the motions of moving objects
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2 Deformation Deformation involves Stress - force applied to a given area 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 slippage that occurs between individual playing cards when the top of the stack is moved relative to the bottom Deformation Strain – changes in the shape or size of a rock body caused by stress How rocks deform Rocks subjected to stresses greater than their own strength begin to deform usually by folding, flowing, or fracturing Deformation How rocks deform General characteristics of rock deformation Elastic deformation – the rock returns to nearly its original size and shape when the stress is removed Once the elastic limit (strength) of a rock is surpassed, it either flows ( ductile deformation ) or fractures ( brittle deformation )
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