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Crustal Deformation

Crustal Deformation. Economic Consequences of Geologic Structures. Tracing Coal Seams, Aquifers, etc. Ore Deposits are often localized along faults and folds Petroleum Traps. Anticlines and Synclines. Monoclines and Homoclines. Axial Plane. How Fast Can Folds Form?. Which Way was Up?.

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Crustal Deformation

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  1. Crustal Deformation

  2. Economic Consequences of Geologic Structures • Tracing Coal Seams, Aquifers, etc. • Ore Deposits are often localized along faults and folds • Petroleum Traps

  3. Anticlines and Synclines

  4. Monoclines and Homoclines

  5. Axial Plane

  6. How Fast Can Folds Form?

  7. Which Way was Up? Sedimentary Structures are governed by: • Gravity • Exposure to the Surface They all have a “right way up”

  8. Foliation Foliation is a sheetlike structure that forms when rocks are deformed.

  9. Foliation • Flattening • Grain Rotation • Solution • New Minerals • Partial Melting • Shearing

  10. Foliation In every case, the foliation is: • In the direction of least resistance • at right angles to the direction of greatest compression.

  11. Folds and Foliation • On a small scale (microscopic to centimeters), foliation forms by a variety of mechanisms, but always at right angles to the direction of greatest compression • On a large scale (centimeters to kilometers), rocks fold. The axial plane of the fold is also at right angles to the direction of greatest compression

  12. Folds and Foliation

  13. The Importance of Minor Folds

  14. How Geologists Use These Clues • Here's an outcrop that might be seen in the field.

  15. How Geologists Use These Clues • Picture the axial plane of the fold as parallel to the foliation. • The other side of the fold is roughly a mirror image of the side we can see.

  16. How Geologists Use These Clues • We can mentally fill out the sketch to get an idea of the shape of the fold. • Note that we still have no idea how big the fold is, only what kind it is.

  17. What if we did it the other way?

  18. Isostasy

  19. The Airy Model

  20. The Pratt Model

  21. Both Ideas are Correct at Times

  22. How Isostasy Works

  23. Isostatic Rebound in Canada

  24. Isostatic Rebound in Scandinavia

  25. Domes and Basins

  26. Domes and Basins

  27. Domes and Basins

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