DEFORMATION OF THE
CRUST

DEFORMATION
 Is the process by which the crust is
deformed along tectonic plate
margins.
 Deformation produces a variety of
geologic structures such as folds and
faults.

Each rock type deforms differently when stress is
gradually applied.
That is to say rocks respond to stress by deforming
elastically.
This is what we call elastic deformation.
Like a rubber band, the rock will return to nearly
its original size when the force is removed. This
process is the same thing that happens for most
earthquake.

There are 2 kinds of Elastic deformation once the
elastic limit or strength of a rock is surpassed:
 Its either flows which
we call ductile
deformation
 It fractures in what we
call brittle deformation.

In other words, for deformation of rock to occur,
the following conditions must be met:
1. The rock material must have the ability to deform under pressure
and heat.
2. The higher the temperature of the rock the more elastic it
becomes.
3. Pressure must not exceed the internal strength of the rock,
otherwise, fracturing occurs.
4. Deformation must be applied slowly.

In general, you can say that a rock has been
deformed if it has been:
Translated from its original position
Changed in orientation
Changed in shape

FOLDS
• Fold can be defined as a bend in rock that
is a response to compressional force.
• It can be likened to the waves in the
ocean.
• Earth has a crest or uphold.
• And a trough od down fold.
• Folds are most visible in rocks that
contained layering.

3 TYPES OF FOLDS
o The common types of folds
are the, anticline, syncline,
and monocline.
o Anticline - is a convex up
fold in rock that resembles an
“arch like”.

o Syncline – a type of
fold where the rock
layers are warped
downward.

o Monocline – the simplest
type of fold which involves
a slight bend in otherwise
parallel layers of rock.

FAULTS
 Faults form in rocks when the
stresses overcome the Internal
strength of the rock resulting in a
fracture.
 It is defined as the displacement
of once connected blocks of
rocks along a fault plane.

 There are several kinds of faults, which are
named according with the type of stress that
acts on the rock and by the nature of the
movement of the rock blocks or either side of
the fault plane.

TYPES OF FAULTS
 Dip-slip Fault – are faults in which
the movement is primarily parallel to
the inclination or dip of the fault
surface.

2 Major Types of Dip-slip Fault
 Normal Fault – occurs
when tensional forces act
in opposite directions. This
is sometimes called
“gravity fault”.

o Reverse Fault – reverse
fault develops when
compression forces exist.
Compression cause one
block pushed up and over
the other block.

GRABEN FAULT
 Produced when tensional
stresses result in the
subsid90ence of a block of
rock. On a large scale these
features are known as rift
valleys.

HORST FAULT
The development of two
reverse fault causing a
block of rock to be
pushed up.

STRIKE-SLIP FAULT
 Are vertical in nature
and are produced
where the stresses are
exerted parallel to
each other.

OBLIQUE-SLIP FAULT
• Happens when
many faults are
mixed in slip
type.

Evidence for Sea-Floor Spreading
 Drilling Samples – samples of rock
from the ocean floor showed rocks
farthest away from the ridge the oldest
and the closest rocks were the newest.

ACTIVITY
Fill in the blank!
1. ________________ is the process by which the crust is deformed along tectonic
plate margins. (1 pt.)
2. ____________________ can be defined as a bend in rock that is a response to
compressional force.(1 pt.)
3. ____________________ a type of fold where the rock layers are warped downward
(1 pt.)
4. _____________________ are faults in which the movement is primarily parallel to the
the inclination or dip of the fault surface. (1 pt.)
5. ______________________develops when compression forces exist. Compression
cause one block pushed up and over the other block. (1 pt.)

6. Enumerate the 3 types of Folds. (3 pts.)
7. Write your own understanding in fault? (2
pts.)
8. What are the types faults? (5 pts.)
9. Enumerate the 2 Major types of Dip-Slip Fault.
(2 pts.)
10. Draw the Graven Fault? (2 pts.)

11. Which evidence that show the involves measurement of
magnetic-field orientations in rocks. (1pt)
12. What are the three types of evidence continental drift
theory? (3 pts)
13. What are causes of seafloor spreading? (2 pts)
14-15. Draw the Seafloor Spreading and explain (5 pts.)