deformation
Upcoming SlideShare
Loading in...5
×

Like this? Share it with your network

Share
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
  • Excellent
    Are you sure you want to
    Your message goes here
No Downloads

Views

Total Views
335
On Slideshare
335
From Embeds
0
Number of Embeds
0

Actions

Shares
Downloads
11
Comments
1
Likes
2

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. Grotzinger • Jordan Understanding Earth Sixth Edition Chapter 7: DEFORMATION Modification of Rocks by Folding and Fracturing © 2011 by W. H. Freeman and Company
  • 2. Chapter 7: DeformationModification of Rocks by Folding and Fracturing
  • 3. About Deformation • Deformation mainly occurs near plate boundaries. • Field observations of deformation show us how to reconstruct geologic history. • Deformation includes faulting of rigid rocks and folding of rocks that can be bent.
  • 4. Lecture Outline 1. Plate tectonic forces 2. Mapping geologic structure 3. How rocks deform 4. Basic deformation structures 5. Unraveling geologic history
  • 5. 1. Plate Tectonic Forces ● Deformation ● tensional forces ● compressive forces ● shearing forces
  • 6. 2. Mapping Geologic Structure ● Outcrop – basic source of geologic information in the field
  • 7. 2. Mapping Geologic Structure
  • 8. 2. Mapping Geologic Structure
  • 9. 2. Mapping Geologic Structure
  • 10. 2. Mapping Geologic Structure ● Measuring strike and dip ● strike is the compass direction of a rock layer as it intersects a horizontal surface ● dip is the amount of tilting of the layer and is measured at right angles to strike
  • 11. 2. Mapping Geologic Structure N W S ion Strike d ect irecti dir on Dip 45° Dip angle E N W S 45° Dip angle E
  • 12. 2. Mapping Geologic Structure N W S ion Strike d ect irecti dir on Dip 45° Dip angle E N W S Water trickles down slope parallel to dip. 45° Dip angle E
  • 13. Dinosaur Ridge, located west of Denver, Colorado.
  • 14. 2. Mapping Geologic Structure ● Geologic maps ● geologic maps represent the rock formations exposed at Earth’s surface ● a common scale for geologic maps is 1:24,000
  • 15. 2. Mapping Geologic Structure ● Geologic cross sections ● geologic cross sections – diagrams showing the features that would be visible if vertical slices were made through part of the crust
  • 16. 3. How Rocks Deform ● Rock behavior in the laboratory ● brittle ● ductile
  • 17. 3. How Rocks Deform An undeformed sample
  • 18. Under conditions representative of the shallow crust, the marble is brittle. An undeformed sample
  • 19. Under conditions representative of the shallow crust, the marble is brittle. Under conditions representative of the deeper crust, marble is ductile. An undeformed sample
  • 20. 3. How Rocks Deform ● Rock behavior in the Earth’s crust ● depths affect brittle v. ductile ● rock type affects way rocks deform ● rate of deformation is a factor
  • 21. 4. Basic Deformation Structures ● Types of faults ● dip-slip – normal, reverse, and thrust ● strike-slip – right- and leftlateral ● oblique-slip
  • 22. 4. Basic Deformation Structures
  • 23. Example of a strikeslip fault
  • 24. 4. Basic Deformation Structures ● Types of folds ● symmetrical folds anticlines and synclines ● asymmetrical folds ● overturned folds ● plunging folds
  • 25. 4. Basic Deformation Structures
  • 26. 4. Basic Deformation Structures
  • 27. 4. Basic Deformation Structures ● Circular structures ● dome ● basin
  • 28. Example of a dome
  • 29. Example of a basin
  • 30. 4. Basic Deformation Structures ● Other features ● joints ● deformation (cataclastic) textures ● fault breccia ● mylonite
  • 31. joints
  • 32. fault breccia
  • 33. mylonite
  • 34. 5. Styles of Continental Deformation ● Tensional tectonics ● Compressive tectonics ● Shearing tectonics
  • 35. 5. Styles of Continental Deformation
  • 36. 5. Styles of Continental Deformation
  • 37. 5. Styles of Continental Deformation
  • 38. Example of tensional tectonics
  • 39. Example of compressive tectonics
  • 40. Example of shearing tectonics
  • 41. Thought questions for this chapter The submerged margin of a continent has a thick layer of sediments overlying metamorphic basement rocks. That continental margin collides with another continental mass, and the compressive forces deform it into a fold and thrust belt. During the deformation, which of the following geologic formations would be likely to behave as brittle materials and which as ductile materials? (a) sedimentary formations in the upper few km (b) metamorphic basement rocks at depths of 5-15 km (c) lower crustal rocks below 20 km In which of these layers would you expect earthquakes?
  • 42. 6. Unraveling Geologic History ● Geologic history is a succession of episodes of deformation and other geologic processes. ● Can be described in time steps 1, 2, 3, …
  • 43. TIME 1 Sediments are deposited on the seafloor.
  • 44. TIME 2 Compressive forces cause folding and faulting. compressive forces faults
  • 45. TIME 3 Uplift is followed by erosion, which creates new horizontal surface.
  • 46. TIME 4 Volcanic eruptions cover the surface with lava flows. lava flows
  • 47. TIME 5 Tensional forces cause normal faults, creating down-dropped blocks and breaking up earlier features. tensional forces normal faults
  • 48. Key terms and concepts Anticline Basin Brittle Compressive force Deformation Dip Dip-slip fault Dome Ductile Fault Fold Foot wall Formation Geologic cross section Geologic map
  • 49. Key terms and concepts Joint Normal fault Shearing force Strike Strike-slip fault Tensional force Thrust fault