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Structural Geology . Deformation of rocks produces: folds, joints, faults. Monocline - southeastern Utah. Northeastern California - note tilted layers. http://faculty.uaeu.ac.ae/~afarrag/physical%20geology/GEODE1.jpg. Wasatch Front NE of Salt Lake City, UT. Types of Stresses.
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Structural Geology Deformation of rocks produces: folds, joints, faults
http://faculty.uaeu.ac.ae/~afarrag/physical%20geology/GEODE1.jpghttp://faculty.uaeu.ac.ae/~afarrag/physical%20geology/GEODE1.jpg
Types of Stresses • Compressive →☐← rocks are squeezed • Tensile ←☐→ rocks are pulled apart • Shear ↑☐↓ rocks are sheared
Responses to Stress • Folding - produced by compressive stress on ductile rocks • Joints, Faults - produced by any type of stress on brittle rocks
Folding • Anticlines - where layers are warped upward • Synclines - where layers are warped downward • Compression of ductile rocks produces alternating anticlines and synclines http://piru.alexandria.ucsb.edu/~geog3/concept_illus/1015_ex1.jpg http://myweb.cwpost.liu.edu/vdivener/notes/faults_folds.gif
Strongly Folded Rock • Note quartzite layer folded back on itself - Baraboo, WI
Joints • Fractures in rock along which no movement has occurred - can form in response to any type of stress • Often promote mechanical weathering since they provide access for water Yellowstone Natl Park, WY Devil’s Postpile Natl Mon, CA
Faults • Fractures in rock along which movement has occurred • Different styles reflect different stresses Canyonlands Natl Park, UT Merrimac Valley, NH
Dip-slip Faults • Best seen in cross-section view (vertical offsets) • Normal Faults - upper block slides down (tensional stress) • Reverse Faults - upper block is pushed up (compressional stress) http://northonline.northseattle.edu/gel101tb/images/fault2.jpg
Strike-slip Faults • Result from shear stresses - best seen in map view (horizontal offsets) • Right-lateral vs. left-lateral http://epod.usra.edu/archive/images/carrizoplain.jpg
Bedrock Geology of Connecticut http://soconnell.web.wesleyan.edu/courses/ees106/field_trips/ct_tectonics/images/CT_bedrockgeology_fault_enh.gif
Bedrock Geologic Map of Massachusetts Features to Note: N-S “striping”: compression from E-W NE-SW “striping” in E Cape consists of recent glacial sediment http://z.about.com/d/geology/1/0/B/J/massgeomap.png