1 / 21

Chapter 9 – FOLDS, FAULTS & GEOLOGIC MAPS

Chapter 9 – FOLDS, FAULTS & GEOLOGIC MAPS. Rock Deformation. Stress Force acting on surface, per unit area Pressure Confining (uniform) Stress is equal from all directions Differential stress Stress is stronger from some directions Strain

renata
Download Presentation

Chapter 9 – FOLDS, FAULTS & GEOLOGIC MAPS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 9 – FOLDS, FAULTS & GEOLOGIC MAPS

  2. Rock Deformation Stress Force acting on surface, per unit area Pressure Confining (uniform) Stress is equal from all directions Differential stress Stress is stronger from some directions Strain Change in rock shape or volume in response to stress

  3. Tension Divergent boundaries Normal faults Compression Convergent boundaries Reverse faults Shear Transform boundaries Strike-slip faults Rock Deformation

  4. Elastic deformation Temporary change; rebounds when stress is gone Elastic limit (AKA yield point) Ductile deformation Permanent, gradual change; folds or bends AKA Plastic deformation Brittle deformation Permanent change; breaks or cracks Rock Deformation

  5. Factors affecting rock deformation Temperature Confining pressure Rate of deformation Composition Structural geology Study of stress & strain Strike Compass orientation of line of intersection between horizontal plane & planar feature Dip Angle between tilted surface & horizontal plane Rock Deformation & Structural Geology

  6. Faults & fractures: Dip-slip faults Normal fault Hanging wall moves downward relative to footwall below Reverse fault Hanging wall moves up & over footwall below Thrust fault Reverse fault with shallow dip angle Structural Geology

  7. Strike-slip fault Movement is horizontal & parallel to strike of fault Right-lateral Left-lateral San Andreas Fault Structural Geology

  8. Folds Bend or warp in layered rock Monocline 1-sided fold Anticline Layers fold upward (arch) Older rocks in core Syncline Layers fold downward (trough) Younger rocks in core Dome Broad area of up-warping Basin Broad area of down-warping Structural Geology

  9. Geologic Maps Geologic map Shows locations, kinds, & orientation of rock units Shows structural features Topographic maps Shows shape of ground surface, as well as location & elevation of surface features Relief Contour lines Geologic cross section Diagram of geologic features underground

  10. Chapter 10 –METAMORPHISM: NEW ROCKS FROM OLD

  11. What is Metamorphism? Metamorphism Mineralogical, textural, chemical & structural changes in rocks Rocks exposed to elevated temperatures &/or pressure Rocks do NOT melt

  12. Factors that influence metamorphism Temperature 150°C = “official” boundary between diagenesis & metamorphism Pressure Composition Pore fluids Pores Open spaces in rocks Migmatite Transition between metamorphic & igneous rocks What is Metamorphism? stress stress

  13. Factors that influence metamorphism (cont’d) Stress Foliation Planar arrangement of textural features in metamorphic rock Gives rock layered or banded appearance Duration Rate of metamorphism What is Metamorphism?

  14. Grade Degree of temperature & pressure a rock is exposed to during metamorphism Low-grade Low temperature & pressure conditions; minimal rock changes High-grade High temperature & pressure conditions; significant rock changes What is Metamorphism?

  15. Metamorphic Rocks • Texture: foliation • Composition: minerals present

  16. Metamorphic Rocks Rocks with foliation Slate Very fine grained metamorphic rock; low grade Metamorphic product of shale Phyllite Fine grained metamorphic rock; intermediate grade Further metamorphism of slate

  17. Metamorphic Rocks Rocks with foliation Schist Visible individual mineral grains; intermediate grade Further metamorphism of phyllite Gneiss Course grained, high grade, strongly foliated (light/dark bands) Further metamorphism of schist

  18. Rocks without foliation Quartzite Metamorphosed sandstone Marble Metamorphosed limestone Metamorphic Rocks

  19. Type of metamorphism Contact metamorphism Rocks heated & chemically changed adjacent to magma intrusion Aureole Burial metamorphism Occurs after diagenesis Due to burial of sediments in deep sedimentary basins Metamorphic Processes

  20. Type of metamorphism Regional metamorphism Metamorphism of extensive area of crust Plate convergence, collision, subduction Other types of metamorphism Fault zone Shock Pyro-metamorphism Metamorphic Processes

  21. Metamorphic Facies Index minerals Minerals that form at specific temperature & pressure conditions Isograds Lines of equal grade Used to map index minerals

More Related