1. FOLDS, FAULTS AND GEOLOGIC MAPS

2. Objectives Define three types of stress.
Describe the differences between elastic, brittle, and ductile deformation.
Define cratons and orogens.
Define strike and dip.
Define and describe synclines, anticlines, and other types of folds.
Distinguish between a topographic map and a geologic map.

3. Rock Deformation Stress Pressure
The force acting on a surface, per unit area
May be greater in certain directions than in others
Pressure
A kind of stress in which the forces acting on a body are the same in all directions

4. Rock Deformation Tension Compression
A stress that acts in a direction perpendicular to and away from a surface
Compression
Stress that acts in a direction perpendicular to and toward surface

5. Rock Deformation Shear Strain
A stress that acts in a direction parallel to a surface
Strain
A change in shape or volume of a rock in response to stress
Uniform stress causes change in volume only
Differential stress may causes change in shape

6. Rock deformation Elastic deformation
Temporary change in shape or volume from which a material rebounds after the stress is removed

7. Rock deformation Ductile deformation
Permanent but gradual change in shape or volume of a material, caused by flowing or bending

8. Rock deformation Brittle deformation
Permanent change in shape or volume, in which a material breaks or cracks

9. Rock Deformation Main factors that affect rock deformation Temperature
Confining pressure
Rate of deformation
Composition

10. Rock Deformation Where rock deformation occurs Craton Orogen
A region of continental crust that has remained tectonically stable for a very long time
Orogen
An elongated region of crust that has been deformed and metamorphosed through a continental collision
Isostasy
The flotational balance of the lithosphere on the asthenosphere

11. Rock Deformation

12. Rock Deformation

13. Structural Geology Structural geology - the study of:
Stress and strain
Processes causing stress and strain
Deformation and rock structures that result from stress and strain

14. Structural Geology Strike Dip
The compass orientation of the line of intersection between a horizontal plane and a planar feature (e.g. rock layer or fault)
Dip
The angle between the tilted surface and a horizontal plane

15. Structural Geology

16. Structural Geology Faults and fractures Normal fault
The block of rock above the fault surface moves downward relative to the block below

17. Structural Geology

18. Structural Geology Faults and fractures Reverse fault Thrust fault
The block on top of the fault surface moves up and over the block on the bottom
Thrust fault
A reverse fault with a shallow angle of dip

19. Structural Geology Strike-slip fault
A fault in which the direction of the movement is mostly horizontal and parallel to the strike of the fault
San Andreas Fault

20. Structural Geology

21. Structural Geology Folds Monocline Anticline
A bend or warp in a layered rock
Monocline
A local steepening in otherwise uniformly dipping strata
Anticline
A fold in the form of an arch, with the rock strata convex upward and the older rocks in the core

22. Structural Geology Syncline
A fold in the form of a trough, with the rock strata concave upward and the younger rocks in the core
The geometry and the orientation of a fold is described by the:
Axial plane
Flanks
Limbs
Axis
Hinge

23. Structural Geology

24. Structural Geology

25. Structural Geology

26. Structural Geology

27. Geologic Maps Geologic map…
Shows the locations, kinds, and orientation of rock units
Shows structural features such as faults and folds

28. Geologic Maps

29. Geologic Maps

30. Geologic Maps Making and interpreting geologic maps Topographic maps…
Show the shape of a ground surface, as well as the location and elevation of surface features, usually by means of contour lines

31. Geologic Maps

32. Geologic Maps

33. The Canadian Rockies

34. Critical Thinking
Which orogens in North America would you expect to have the deepest roots, and how could you test your hypothesis?
In the figure below, which strata in the photograph are the oldest and how can you tell?