Word List for Lecture Test 2 GY 111 Lecture test 2 preparation Essay Question for Lecture Test 2 Discuss one of the following depositional environments Alluvial fans Beaches meandering rivers In your answer which must have good illustrations make sure you discuss the major processes that control sedimentation as well as the rock types that are deposited in the environment you have selected to discuss Last Time wow A Maps B Stratigraphic principles C Beds in 3D space the problem of orientation D Strike and Dip E Geological maps 1 horizontal and inclined bedding UNIVERSITY OF SOUTH ALABAMA GY 111 Physical Geology Lecture 20 Rock Deformation Geology maps Show the geology at the surface of the Earth http www geo ua edu Documentation jpgs GeoMap jpg 1 Stratigraphy Stratigraphic Principles 1 The principle of superposition that states in any sedimentary succession that has not been overturned the oldest strata occur on the bottom Stratigraphy the study classification and correlation of rock layers and layering Beds in 3D Space All sedimentary beds are initially deposited in horizontal sheets strata But you may not initially appreciate this with my 2D cartoons Beds in 3D Space 2 The principle of original horizontality that states sedimentary layers are originally deposited as horizontal sheets 3 The principle of original lateral continuity that states that sedimentary layers are originally deposited as laterally continuous sheets that naturally terminate against basin margins or barriers or which grade into other sedimentary layers Geological Maps 1 Inclined bedding leads to more complex geological maps but they are still interpretable if you know the rules which you will get in an upcoming assignment Today s Agenda Rock Deformation A Confining pressure and rock deformation B Elastic versus permanent deformation C Types of deformation Web notes 20 Strike The orientation of the inclined bed 0 to 360 Dip The inclination of the inclined bed 0 to 90 2 Rock Deformation Rock Deformation Orientation or attitude sedimentary bedding starts off horizontal but can be deformed into any configuration Rock deformation any change in the volume shape or orientation of a rock body Law of Original Horizontality Law of Superposition Stress Strain Rock Deformation Stress a force applied to an area Example tire pressure in psi Strain the amount of deformation produced by stress Elastic strain analogous to a steel spring or rubber band Plastic strain analogous to deforming mud or putty Brittle strain analogous to breaking glass The strength of materials including rocks can be tested in labs using hydraulic presses All materials behave elastically up to a point Once past the elastic limit deformation becomes permanent Stress vs Strain Diagrams z z Illustrate the mechanical behavior of rock materials Ductile deformation requires a significant component of plastic mechanical behavior Stress vs Strain Diagrams z z Illustrate the mechanical behavior of rock materials Ductile deformation requires a significant component of plastic mechanical behavior Ductile Deformation Ductile Deformation Elastic Limit Stress Elastic Limit Stress a el st ic Distortion below the elastic limit is 100 recoverable Strain a el st ic Distortion below the elastic limit is 100 recoverable Strain 3 Stress vs Strain Diagrams z z Illustrate the mechanical behavior of rock materials Ductile deformation requires a significant component of plastic mechanical behavior Ductile Deformation Stress vs Strain Diagrams z z Illustrate the mechanical behavior of rock materials Brittle rocks near the surface of the Earth behave as brittle materials Brittle Deformation plastic Elastic Limit Elastic Limit Stress Stress a el st ic Distortion below the elastic limit is 100 recoverable Strain z z a el st ic Distortion below the elastic limit is 100 recoverable Strain Stress vs Strain Diagrams Mechanical Behavior of Rocks Illustrate the mechanical behavior of rock materials Brittle rocks near the surface of the Earth behave as brittle materials Near surface rocks that are under low T P conditions behave as brittle material z Fault fracture slippage z Joint fracture no slippage Brittle Deformation Rupture Stress a el st ic Deep rocks under elevated T P conditions behave as ductile material z Folding Distortion below the elastic limit is 100 recoverable Strain Today s Homework Assignment 3 due next Tuesday Lecture Test 2 next Thursday Complete your Christmas shopping by Friday 1 2 3 Next Time 1 Folds Ductile Deformation 4
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