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Published byDominic Henderson Modified over 9 years ago
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Tectonic deformation and geologic structures
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Mountain building Anatomy of a convergent mountain belt Valley & ridge Blue ridge
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Mountain building Continental rift; opening of an ocean basin? Extensional horsts and grabens Horst Graben
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Deformation Deformation: 1)translation 2) rotation 3) distortion (shape change) Deformation results from stress, Stress = force per unit area
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Deformation - types of stress Compressive stress Tensional stress Lateral shear stress
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Uniform pressure from all directions Deformation - tectonic Compression in a principal direction Extension in a principal direction Lateral shear
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Brittle: shallow crust; with increased stress little change until failure (breaks) Ductile: deeper crust; with increased stress gradual change (squishes) Rock deformation: When does it fold and when does it fault? depends on rock type, crustal depth, rate
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Products of deformation Faults Folds
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Anticline: opens downward; oldest rocks in center Syncline: opens upward; youngest rocks in center Types of folds
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Strike and dip measurements along the limbs of a fold Deformation - folds
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domebasin Types of folds
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fold appears to die out on ground surface Plunging folds
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http://www.fault-analysis-group.ucd.ie/papermodels/models/syncline_anticline_lowres.jpg
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Types of faults Thrust faults: Compression HW up shallow dip Normal faults: Extension HW down steep dip
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Types of faults Strike-slip faults: lateral shear no vertical change vertical dip
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(map view) Thrust, strike-slip or normal faults?
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Southern Appalachians - fold and thrust belt Cross-section through western Virginia Interrelated Folds & faults imbricate thrusts West Virginia Virginia North Mtn fault Staunton faultWaynesboro Blue Ridge Rockfish Valley CharlottesvilleGum Spring 10 km
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Mountain building Richmond Basin = continental rift; related to opening of the Atlantic ocean Extensional horsts and grabens Richmond Richmond Basin Yorktown Chesapeake Bay Gum Spring Cape Charles 10 km Cross-section through eastern Virginia
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