An Outline about the Structural geology topic which deals about dynamics of natural deformation.

1. ELEMENTS OF
STRUCTURAL
GEOLOGY
ARUN.A,
RESHMA.B
University College,
Thiruvananthapuram

2. SRUCTURAL GEOLOGY
 Structural geology is the study of the three
dimensional distribution of large bodies of
rock, their surfaces, and their composition.
 We try to learn about their tectonic history,
past geological environments and event that
could have changed or deformed them.

3. DEFORMATION
In earth science, deformation means
alternation of size or shape of rock.
Deformation is caused by,
1. Deformative forces
2.Mechanical properties of Rock
3.Time period
4.Depth of formation

4. 1 DEFORMATIVE FORCES
“The shape and size of a rock material change due
to the action of STRESS.”
What is a Stress?
Stress is the force acting on unit area of a material
surface.

5. There are three types of STRESS
COMPRESIV
E STRESS
It is a force that pushes
the material on opposite
sides of a plane.
TENSILE
STRESS
It is a force that pull apart
the material on opposite
sides of a plane
SHEARING
STRESS
It is a force that causes
layers or parts to slide
upon each other in
opposite directions

6. “When rocks deform they are said to STRAIN”
What is a Strain?
A strain is a change in size, shape, or volume of a
material.

7. 2 MECHANICAL PROPERTIES
OF ROCK
This speaks about the strength of the rocks.
1. BRITTLE - hard but liable to break easily.
2. PLASTIC(Malleable) - permanent deformation under
stress.
3. ELASTIC - able to resume its normal
shape spontaneously after
deformation.

8. A Rock subjected to increasing stress it passes
through 3 successive stages of deformation.
ELASTIC
DEFORMATION
Strain is reversible
DUCTILE (PLASTIC)
DEFORMATION
Strain is reversible
Rearrangement of platy or
flaky minerals (if present)
BRITTLE
DEFORMATION
Irreversible strain where the
material breaks.

9. 3 TIME
•A Small force acting over a great length of time
can bring about the same type of structure like
that produced by a large force acting over a short
period of time.
•Forces that are unable to deform rocks may
cause rock to flow, if it is maintained for a long
period of time.

10. 4 DEPTH OF FORMATION
•A Rock situated in the shallow depth and
greater depth behave differently.
•Physical properties like Temperature, Litho
static pressure differ with respect to depth.
•The factor of Depth is called by the term
“Environment of Structural deformation”

11. From above details Structures seen in Earth is
of two types
STRUCTURES
RUPTURE
STRUCTURES
PLASTIC
STRUCTURES

12. RUPTURE STRUCTURES
FRACTURE
A Fracture is any separation in a
geologic formation
JOINT
A Joint is a fracture dividing rock
into two sections that have not
moved away from each other.

13. FAULT
Planar fracture or discontinuity
in a volume of rock, across
which there has been
displacement of rock-mass .
SHEAR
Response of a rock to deformation
usually by compressive stress and
forms particular textures.

14. PLASTIC STRUCTURES
FOLDS
One or a stack of originally flat
and planar surfaces are bent
or curved as a result of
permanent deformation
FOLIATION
Repetitive layering in
metamorphic rocks
LINEATION
Linear structural features within
rocks

15. MEASUREMENT OF GEOLOGIC
STRUCTURES
•All geologic structures are mathematical models
we designed for studying.
•To convert these real life figures to mathematical
data we need to be aware of certain terms.

16. 1. OUTCROP
Any Geological formation exposed on the surface is
called an OUTCROP

17. 2. STRIKE & SLIP
STRIKE - Direction in which a geological structure is
present.
*STRIKE DIRECTION may be defined as direction of trace of
Intersection between horizontal plane and the bedding plane
*Usually Clinometer compass or Brunton compass are used
to measure STRIKE.

19. DIP - It means SLOPE or INCLINATION.
Expressed both as amount and direction.
*Dip direction- Direction along which inclination of bedding plane
occurs.
*Dip amount - Angle at which a planar feature is inclined to the
horizontal plane

20. STRIKE direction will always be
perpendicular to DIP direction.
Apparent dip is the name of any dip
measured in a vertical plane that is not
perpendicular to the strike line