2. OBJECTIVES:
At the end of the presentation, you
should be able to know about the
following:
• Definition of Diastrophism
• Theories explaining Diastrophism
• Stress and Strain
• Faults and Folds

3. Defining DIASTROPHISM:
Tectonism
deformation of Earth’s crust by
natural processes (movements)
leads to the formation of continents
and ocean basins, mountain
systems, plateaus, rift valleys, and
other features.

4. TRIVIA:
Do you know that?
Due to Earth’s gravity it is impossible
for mountains to be higher than
49, 000 feet (15,000 metres).

5. How does Diastrophism occur?

6. 1.) Isostasy Theory
 state of gravitational
equilibrium between
the Earth's
lithosphere and
asthenosphere
 tectonic plates "float"
at an elevation
which depends on
their thickness and
density.

7. Simple Analogy:

8. Example:
North
Greenland
fjord cliffs

9. TRIVIA:
 Thegeneral
term 'isostasy'
was coined in
1889 by the
American
geologist
Clarence
Edward Dutton.

10. 2.) Contraction Theory
Earth is SHRINKING.
Gravity draws the
crust inward causing
it to bend, buckle
and trench.

11.  Shrinking
resulted in a
reduction in the
Earth’s diameter
while the
circumference
remained
unchanged due
to folding and
buckling of the
crust

12. 3.) Convection Current Theory
 convection
within the
Earth's mantle
pushes the
plates
 movement of a
fluid, caused by
differences in
temperature

13. According to this theory:
 Theplate is the cooled surface
layer of a convection current in
upper mantle.

14. 4.) Continental Drift Theory
 Continents were
joined in a
super-continent,
called Pangaea
(all lands). Over
a vast period of
time, the
continents
drifted apart to
their current
locations.

15. Some Evidences:
 The jigsaw fit
of the outline
of the
continental
margins.

16. Fossils

17.  Numerous
geological
similarities
between
South
America and
Africa.

18. TRIVIA:
 Continental
Drift theory
was first
presented by
Alfred Wegener
who died two
days after his
50th birthday.

19. 5.) Expansion Theory
 Earth
is physically expanding in
diameter, mass, or both.

20. 6.) Plate Tectonics Theory
 Earth's outer
layer is
fragmented
into plates
that are in
constant
motion.

21. Plate Boundaries and Their Motions
 Divergent
 Convergent
 Transform/
Thrust

22. Major Earth Movements
 Uplift
 Subsidence

23. TRIVIA:
Do you know
that?
On every
continent
there is a city
called Rome.


24. STRESS AND STRAIN
3 main concepts about stress and strain:
rocks deform,
stress causes strain and strain results in
structures,
different physical conditions create
different structures

25. STRESS is a
Force
acting on
some areas

26. 3 BASIC TYPES OF STRESS
Compressional Stress
Tensional Stress
Shear Stress

27. STRESS AND STRAIN
Strain is a change in size,
shape, or volume of a material.
Response to stress

28. 3 BASIC TYPES OF STRAIN
Elastic Strain
Plastic Strain
Fracture Strain

29. NOTE :
 Stresscan
happen with
out strain, but
strain cannot
happen
without stress.

30. 2 Major Types of
Structural Deformation
 Fault
 Fold

31. Fault
 rocksbreak due to force
4 types:
Normal Fault
Reverse Fault
Strike-Slip Fault
Thrust Fault

33. Fold
 Rocks bend due to force
Types of Fold:
 Symmetrical Folds
 Assymetrical Folds
 Isoclinal Folds
 Overturned Folds
 Recumbant Folds
 Chevron Folds

37. REPORTED BY:
CLARISSE P. CACAPIT

38. Syncline
 youngestrocks occur in the core of a fold
 Caused by compressional stress
 U-shaped

39. Anticline
 oldest
rocks occur in the core of a fold
 Caused by compressional stress
 A-shaped

45. Compressional Stress
 two plates
move
together or
one moves
and applies a
force on
another one
that is not
moving.

46. Tensional Stress
 one part of a
plate moves
away from
another part
of a plate.

47. Shear Stress
 two plates
slide past one
another

48. Elastic Strain
rocks
recover to
their
original
shape.

49. Plastic or Ductile Strain
 Rocks do
not return
to their
original
shape.

50. Fracture or Brittle Strain
rocks crack
or break
under the
stress.