Lecture 18

Lecture 18 - Observe the Observe topography of part of the...

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Unformatted text preview: Observe the Observe topography of part of the Ridge the and Valley Province 08.00.a Force and Stress Force is push or pull, expressed Force as amount of acceleration experienced by a mass experienced What happens if same amount of What force is applied to two wooden pillars? force Stress = force per area per 08.01.a How Rocks Respond to Force and Stress Small amount of stress: block remains unchanged 08.01.b Displacement Strain Rotation Professor Wenlu Zhu Geology Univ of Maryland Rock Physics Lab Yes, we do such studies here! Consider the structural behavior of rocks at shallow Consider versus deep conditions versus 08.01.c At shallow At depths, most rocks break rocks Temperature and Temperature pressure increase with depth with Rocks flow Rocks in deep conditions conditions Consider how minerals respond at shallow versus Consider deep conditions deep Shallow: Shallow: minerals may be unaffected unaffected Deep: Deep: minerals may recrystallize recrystallize 08.01.c Different Kinds of Stress Confining Confining pressure pressure Differential Differential stress stress Fluid pressure Fluid counteracts stress stress 08.02.a Strength of Rock Small Small stress stress Increase Increase stress stress Too much Too stress = failure failure Strength of continental Strength crust crust 08.02.b Observe three kinds of stress and resulting structures Compression Tension Shear Shallow levels: rocks fracture Deeper levels: rocks flow 08.02.c Types of Fractures Joint: Joint: crack where rock pulled apart apart Fault: rocks Fault: have slipped past one another another 08.03.a Stresses that Form Joints Burial and Burial tectonic forces tectonic Cooling and Cooling contraction contraction Unloading 08.03.c Describing Faults Strike Dip 08.04.a Strike-slip Strike-slip fault fault Dip-slip fault Oblique-slip fault Sense of Movement Hanging wall Footwall 08.04.b Normal fault Reverse fault or Reverse thrust fault thrust Strike-Slip Faults Rocks move Rocks horizontally 08.04.c Left lateral Right lateral Folds Layers can Layers be folded be Anticline Syncline Anticline Syncline 08.05.a Domes and Basins Dome Basin 08.05.a Monocline 08.05.a Geometry of Folds g in H e Limb 08.05.b Limb Plunging Plunging fold fold Axial Surface Upright fold Asymmetric fold Overturned fold Rock Cleavage Cleavage Cleavage plane plane 08.06.a Foliation 08.06.b Schistosity Gneissic foliation Flattened pebbles Foliation from shearing Lineation Oriented minerals Stretched crystals Shearing marks 08.06.c Other Metamorphic Features Preserved features Preserved Shear zone Folded pebbles Folded Deformed foliation 08.06.d Metamorphism of Sedimentary Rocks Increasing metamorphism of shale Increasing 08.07.a Slate Schist Sandstone Sandstone becomes quartzite quartzite Limestone Limestone becomes marble marble Gneiss ...
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This note was uploaded on 01/24/2011 for the course GEOL 100 taught by Professor Martin during the Fall '08 term at Maryland.

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