How rocks behave under different types of stress (Earth Science)

1. How rocks behave
under different
types of stress

2. Objectives
2
⊷ Understand how rocks are
deformed by stress and undergo
solid deformation.
⊷ Explain how tension, compression,
and shear stresses produce
geological structures.

3. Motivation
But before our lesson, let’s play
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4. SESTRS4

5. STRESS5

6. 6

7. STURC7

8. CRUST8

9. 9

10. STANIR10

11. STRAIN11

12. 12

13. TEALSIC13

14. ELASTIC14

15. 15

16. CORK16

17. ROCK17

18. 18

19. Body of the
Report
19

20. Stress Vs.
Strain

21. Strain
⊷ When rocks deform they are
said to strain.
⊷ A strain is a change in size,
shape, or volume of a
material.
21

22. Stress
⊷ The forces acting on rock are
called stress. Stress is the
force applied on a rock per
unit area.
22

23. Types of
Stress

24. Types of Stress
⊷ Tensional Stress
⊷ Compressional Stress
⊷ Shear Stress
24

25. Tensional Stress
⊷ Tension stresses act in
opposite directions, pulling
rock apart or stretching it
25

26. 26
Tensional Stress

27. Compressional Stress
⊷ Compression stresses act
toward each other, pushing
or squeezing rock together.
27

28. 28
Compressional Stress

29. Shear Stress
⊷ Shear stresses may act
toward or away from each
other, but they do so along
different lines of action,
causing rock to twist or tear.
29

30. 30
Shear Stress

31. Stages of
Deformation

32. Stages of Deformation
⊷ Elastic Deformation
⊷ Ductile Deformation
⊷ Fracture
32

33. Elastic Deformation
⊷ wherein the strain is
reversible.
33

34. Ductile Deformation
⊷ wherein the strain is
irreversible.
34

35. Fracture
⊷ irreversible strain wherein the
material breaks.
35

36. Factors
Affecting
Deformation

37. FACTORS AFFECTING
DEFORMATION
⊷ Temperature
⊷ Confining Pressure
⊷ Strain Rate
⊷ Composition
37

38. Temperature
⊷ At high temperature
molecules and their bonds
can stretch and move, thus
materials will behave in more
ductile manner. At low
Temperature, materials are
brittle.
38

39. Confining Pressure
⊷ At high confining pressure
materials are less likely to
fracture because the
pressure of the surroundings
tends to hinder the formation
of fractures. At low confining
stress, material will be brittle
and tend to fracture sooner.
39

40. Strain Rate
⊷ At high strain rates material
tends to fracture. At low
strain rates more time is
available for individual atoms
to move and therefore ductile
behavior is favored
40

41. Composition
⊷ Some minerals are very brittle.
This is due to the chemical bond
types that hold them together.
Thus, the mineralogical
composition of the rock will be a
factor in determining the
deformational behavior of the
rock.
41

42. Strike And
Dip

43. Strike
⊷ Strike is the compass
direction of any horizontal line
on the plane.
43

44. Dip
⊷ The dip is the angle between
a horizontal plane and the
inclined plane, measured
perpendicular to the direction
of strike.
44

45. 45
Strike and Dip

46. ROCK
BEHAVIORS

47. Rock Behaviors
⊷ Brittle
⊷ Ductile
47

48. Fracture of Brittle
Rocks
⊷ Joint
⊷ Fault
48

49. Joint
⊷ A joint is a fracture along
which no movement has
taken place, usually caused
by tensional forces.
49

50. Fault
⊷ A fault is a fracture or break
in the rock along which
movement has taken place
50

51. Types Of
Faults

52. Types OF Faults
⊷ Dip-Slip Fault
⊷ Strike-Slip Fault
⊷ Oblique-Slip Fault
52

53. 53

54. 54

55. 55

56. Deformation of Ductile
Rocks
⊷ When rocks deform in a
ductile manner, instead of
fracturing to form faults or
joints, they may bend or fold,
and the resulting structures
are called folds.
56

57. Folds
⊷ Folds result from
compressional stresses or
shear stresses acting over
considerable time.
57

58. Kinds of
Folds

59. Kinds of Folds
⊷ Monoclines
⊷ Anticlines
⊷ Synclines
59

60. Monoclines
⊷ Monoclines are the simplest
types of folds. Monoclines
occur when horizontal strata
are bent upward so that the
two limbs of the fold are still
horizontal.
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61. 61

62. Anticlines
⊷ Anticlines are folds where the
originally horizontal strata has
been folded upward, and the
two limbs of the fold dip away
from the hinge of the fold.
62

63. 63

64. Synclines
⊷ Synclines are folds where the
originally horizontal strata
have been folded downward,
and the two limbs of the fold
dip inward toward the hinge
of the fold.
64

65. 65

66. 66

67. 67
QUIZ
ENUMERATION
1-3 Types of Stress
4-6 Stages of Deformation
7-10 Factors Affecting Deformation
11-13 Types of Faults

68. 68
QUIZ
14. is the compass direction of any
horizontal line on the plane.
15. The is the angle between a horizontal
plane and the inclined plane, measured
perpendicular to the direction of strike.

69. ANSWERS
69

70. 70
ANSWERS
1. Tensional Stress
2. Compressional Stress
3. Shear Stress
4. Elastic Deformation
5. Ductile Deformation
6. Fracture
7. Temperature
8. Confining Pressure
9. Strain Rate
10. Composition
11. Dip-Slip Fault
12. Strike-Slip Fault
13. Oblique-Slip Fault
14. Strike
15. Dip

71. 71
Thanks!
ANY QUESTIONS?

72. Presented by:
Hessy Eya E. Culanag
STEM 3 LOYAL
72