2. Deformation
Is the process by which
the crust is deformed
along tectonic plate
margins.
Deformation produces a
variety of geologic
structures such as folds,
faults, joints, and foliation.
3. 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 earthquakes.
4. ? There are 2 kinds of elastic deformation once the
elastic limit or strength of a rock is surpassed:
1. Its either flows which we call ductile deformation.
2. It fractures in what we call brittle deformation.
5. 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.
8. ? In general, you can say that a rock has been
deformed if it has been:
? Translated (move) from its original position
? Changed in orientation (folding, rotation or
tilting)
? Changed in shape(distortion)
9. Fold
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 or down fold.
Folds are most visible in
rocks that contained layering.
10. 3 types of Folds
? The common types
of folds are the,
anticline, syncline
and monocline.
? Anticline = is a
convex up fold in
rock that resembles
an ¡°arch like¡±
11. ? Syncline = a type of fold
where the rock layers are
warped downward.
? Monocline = the simplest
type of fold which involves
a slight bend in otherwise
parallel layers of rock.
? More complex fold types
can develop in situations
where lateral pressures
become greater. Greater
pressure results in
anticline and synclines
that are inclined and
asymmetrical.
12. 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.
13. ?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.
14. Type 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¡±.
Reverse fault = reverse fault develops when
compression forces exist. Compression cause one
block pushed up and over the other block.
15. Graben Fault
Produced when tensional stresses
result in the subsidence of a block of
rock. On a large scale these features
are known as rift valleys.
16. Horst Fault
? The development of
two reverse fault
causing a block of
rock to be pushed
up.
17. Strike-slip fault
Are vertical in nature and are
produced where the stresses
are exerted parallel to each
other.
A transform fault is a special
kind of strike-slip fault that cuts
through the lithosphere and
accommodates motion
between two large crustal
plates.
