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Understanding Faults: Types, Classification, & Geological Significance

Explore the types of faults, their formation under varying geological conditions, importance of fault studies, and how to classify faults based on nature. Learn about normal and thrust faults with illustrations and examples. Understand strike and dip measurements, fault shapes, and how faults shape landscapes.

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Understanding Faults: Types, Classification, & Geological Significance

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  1. Recognizing faults Practice with thrust faults and normal faults

  2. Why study faults? Classification of faults: - each type of fault forms under different geologic conditions - so, if we can characterize the nature of the fault, we can conclude something about the geologic history...

  3. Some faults are easy to see… • A Normal fault The San Andreas fault - a slip fault

  4. Death Valley (photo by M. Miller) Some are harder to see ……an extensional fault • The fault is here <===(normal fault) <======== The level land has dropped DOWN

  5. strike dip Orientation of fault surfaces: Strike and Dip Note: for mechanical reasons fault planes are seldom planar over long distances…thus, we must take MANY strike and dip measurements along a fault.

  6. Wytch Farm Oil Field, southern England (taken from Kttenhorn & Pollard, AAPG Bull, 2001) The Nature of Fault Shapes • Faults are not infinite • Faults can be irregularly shaped

  7. Strike Slip Fault

  8. http://earthobservatory.nasa.gov/Study/denali/

  9. Oldest fault Compression Newest fault

  10. Compression A thrust fault showing how layers have moved. (black is a layer of coal) Hanging wall Foot wall

  11. Compression: Distortion along a fault • Movement drags on the rock next to this thrust fault. • The layers became bent when the walls moved. Hanging wall Foot wall Fault

  12. Extensional faults (Utah)

  13. Extension • An area of extension is called Basin and Range topography. (the flat areas are basins, the mountains are ranges)

  14. Extension • The fault line is here Hanging wall This lower area has dropped down <==== Foot wall

  15. Extension • Normal faults Foot wall Hanging wall Foot wall Notice this broken layer has moved down.

  16. Extension • Can you see a normal fault in this picture? Hanging Wall The black shale layer has dropped down compared to the other side. Foot Wall http://raider.muc.edu/~mcnaugma/structur.htm

  17. Hanging wall #1 Is this a normal or thrust fault? Foot wall http://virtual.yosemite.cc.ca.us/ghayes/Death_Valley_Friday.htm

  18. #2 Is this a normal or thrust fault? Hanging wall (Same layer) Foot wall http://raider.muc.edu/~mcnaugma/structur.htm

  19. #3 Is this a normal or thrust fault? Hanging wall (older rock) (younger rock) Foot wall http://raider.muc.edu/~mcnaugma/structur.htm

  20. #4 Normal or Thrust fault? www.pitt.edu/.../7Structures/NormalFaults.html

  21. #5 Normal or thrust fault? http://gpc.edu/~pgore/geology/geo101/faults.htm

  22. #6 Thrust or Normal faults?

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