1. Structural Geology Tectonic Stresses  Large Scale Strain of the Crust i.e., Geologic Structures
Crust: Rigid, Thin
Inner core: Solid iron
Outer core: Liquid iron, convecting (magnetic field)
Mantle (Asthenosphere) : Solid iron-magnesium silicate, plastic, convecting
Crust (Lithosphere): Rigid, thin
5-30km
Mantle: Plastic, Convecting

2. Tectonics and Structural Geology
Tectonic Stresses
resulting from
Internal Energy
(heat driving convection)
Strains (deforms) the Mantle and Crust
Bends Rocks, i.e.,
ductile strain (Folds)
Breaks Rock, i.e.,
brittle strain (Joints) and
Moves large blocks along
Faults and
Releases energy 
Earthquakes

3. Folds and Faults (Palmdale, Ca)

4. Eastern Pennsylvania
Northwestern
Africa

5. High Low Northwestern Africa
Metamorphic
Grade
High
Low
Northeastern
North America
Northwestern
Africa

6. Strike and Dip of Planar Feature
Two methods of reporting planar orientation
Quadrant: N15oE, 45oS (geologists)
Azmuthal: 195o/45o (engineers)

7. Stikes and Dips are used to identify geologic structures

8. Brunton Pocket Transit
Clinometer
Azimuthal Compass
Transit

9. Stresses at Plate Boundaries
Divergent
(Tensional)
|
Convergent
(Compressional)
|
Transform
(Shear)
e.g., Pacific NW
Kehew, Fig. 1-20
Lab. Man., Fig. 21-2

10. Geologic Structures
Different stresses result in various forms of strain (geologic structures)
Folds (compressive stresses may cause ductile strain)
Faults (Any type of stress may cause brittle strain. The type of fault depends on the type of stress)

11. Anticline (fold)

12. Syncline (fold)

14. Plunging Anticline

17. Eastern Pennsylvania
Folds and faults resulting from compressive stresses
Anticlines (many plunging)
Synclines (many plunging)
Reverse faults
Thrust faults

18. Domes and Basins

20. Bedrock Geology of the Michigan Basin
During and after the deposition of Michigan’s sedimentary rocks
The crust warped downward
Exposing younger rocks in the center and
Older rocks on the rim (e.g. Toledo)

21. Brittle Strain  Joints
When shallow crust is strained rocks tend to exhibit brittle strain

22. Sheet Joints (due to Expansion and Exfoliation)

23. Fault: Movement occurring along a discontinuity
Brittle strain and subsequent movement as a result of stress
Fault
terminology

24. Faults Fault: When movement occurs along a discontinuity
Fault type depends on the type of stress

26. Normal Faults

27. Normal Faults, Horsts and Grabens

28. Structures at Divergent Boundaries
Tensional Stresses cause brittle strain and formation of sets of normal faults
i.e., Horsts and Grabens

29. Horsts and Grabens
Older Rocks are exposed along the ridges formed by the horsts
Younger rocks lie beneath the grabens
Sediment fills in the linear valleys

30. Nevada “Washboard topography” is the result of Horsts and Grabens
A.k.a, Basin and Range

31. Structural Oil Traps

32. Reverse and Thrust Faults
Compressive stress causes the hanging wall to move upward relative to the foot wall  Reverse Fault
At convergent plate boundaries ancient rocks can be thrust over younger rocks  Thrust Fault

33. Thrust Fault: Glacier NP, Montana
Old
Younger

34. Structures at a Convergent Boundary

35. Structures within Mountain Belts

36. Compressional and Tensional Structures

37. E.g., The Apls
Intense folding and thrusting of sedimentary rocks

38. Strike Slip Faults
Physiographic Features

39. San Andreas Fault What type of fault is this?
What other features are associated with the fault?