Interior Structure of the Earth

Interior Structure of the Earth

1. Geodesy, GE 202
Kutubuddin ANSARI
[email protected]
Lecture 3, Oct 11, 2016
Interior of the Earth

2. •The Earth's mass is about 5.98 x 10
24
kg.
• Earth is the densest planet in our Solar
System (mass/volume).
•Earth is made of several layers with different
compositions and physical properties, like
temperature, density, and the ability to flow.
Earth

3. Crust
Mantle
Core
The Earth is divided into three main layers.
Earth Layers

4. Shell = crust
Egg white = mantle
Yolk = core
How are the earth’s
layers similar to an
egg?
Earth Layers

5. Earth Layers
Crust = 0 to 50 km
Mantle= 50 to 2900 km
Outer Core= 2900 to 5100 km
Inner Core= 5100 to 6371 km

6. Earth Layers

7. The Crust
The Earth’s crust is like
the skin of an apple. It is
very thin compared to the
other three layers.
The crust makes up 1% of
the Earth.
The crust of the Earth is
broken into many pieces
called plates.

8. CrustCrust
•Thinnest layer (0-50 km)
•Two types of crust
Continental crust
Oceanic crust
The Crust

9. Continental
Average 30 km
Oceanic
Average 5-8 km
The Crust

10. The Mantle
•The mantle is the
layer below the crust.
•The mantle is the
largest layer of the
Earth.
•The mantle is divided
into two regions: the
upper and lower
sections.

11. •Extremely Thick! (2,900 km)
•It is too far down to drill
How do we know what it is
made of?
•Like the mineral olivine
•Large amounts of iron
and magnesium
The Mantle

12. The Core

13. The core of the Earth is
like a ball of very hot
metals.
The outer core is liquid.
The outer core is made
up of iron and is very
dense
Outer Core

14. The inner core of the
Earth has temperatures
and pressures so great
that the metals are
squeezed together and
are not able to move.

The inner core is a solid
Inner Core

16. Plate Tectonics

17. Plate Tectonics
•The Earth’s crust is divided into 12 major plates
which are moved in various directions.
•This plate motion causes them to collide, pull
apart, or scrape against each other.
•Each type of interaction causes a characteristic set
of Earth structures or “tectonic” features.
•The word, tectonic, refers to the deformation of
the crust as a consequence of plate interaction.

18. •Plates are made
of rigid
lithosphere.
•The lithosphere is
made up of the
crust and the
upper part of the
mantle.
Plate Tectonics

19. Plate Tectonics
•Below the
lithosphere which
makes up the
tectonic plates is
the asthenosphere.

20. •“Plates” of lithosphere are moved around by
the underlying hot mantle convection cells
Plate Tectonics

21. The lithosphere is broken up into plates that move
horizontally across the Earth.
Earth’s Layered Structure

22. •Divergent
•Convergent
•Transform
Three types of plate boundary

23. Plate Boundaries
Convergent
• Ocean-continent
• Ocean-ocean
• Continent-continent
Plates move away from each other

24. Plate Boundaries
Divergent
•Plates move away from each other
•New crust is being formed

25. Plate Boundaries
Transform
•Plates slide past one another
• Crust is neither created nor destroyed

26. •The earthquakes are not randomly distributed over
the globe
•At the boundaries between plates, friction causes
them to stick together. When built up energy causes
them to break, earthquakes occur.
Figure showing
the distribution of
earthquakes
around the globe
Earthquakes and Plate Tectonics…

28. Length
W
i
d
t
h
DIP Angle
S
l
i
p
Fault
Rake Fault is a planar
fracture or
discontinuity in a
volume of rock, across
which there has been
significant
displacement along
the fractures as a
result of rock mass
movement.
DIP Angle (δ )
Rake (ψ)
Depth

29. Top Depth
Length
W
i
d
t
h
Bottom Depth
Earth Surface
( )
BottomDepth Top Depth
Sin Dip Angle
Width
-
=
Fault

30. Strike-Slip Fault
• The movement of
blocks along a fault is
horizontal.
•Rake zero (0
o
)
Slip

31. •If the block on the far side of
the fault moves to the left,
the fault is called Left-lateral
(sinistral) Fault.
•If the block on the far side
moves to the right, the fault is
called Right-lateral (dextral)
Fault.
Strike-Slip Fault

32. Dip-Slip Fault
• The movement of
blocks along a fault is
vertical.
•Rake (90
o
)
Slip

33. •If the hanging wall moves downward
relative to the footwall, the fault is
called Normal (extensional) Fault.
•If the hanging wall moves upward
relative to the footwall, the fault is
called Reverse Fault. Reverse faults
indicate compressive shortening of the
crust.
• Reverse fault having dip angle less
than 45
0
is called Thrust Fault.
Dip-Slip Fault

34. Normal Fault
Thrust Fault
Reverse Fault
Dip-Slip Fault

35. Oblique-Slip Fault
•A fault which has a
component of dip-slip
and a component of
strike-slip is termed
an oblique-slip fault.
• Rake will be (0 < ψ
>90)
Slip

36. The Geometry of the fault having parameters (length, width, depth,
dip angle) can be given by analytically by Green function (G):
2 2
1 1
AL AW
AL AW
G d d h x=ò ò
L
e n
g th
W
i
d
t
h
DIP
S
l
i
p
Length(AL) W
id
th
(
A
W
)
Length
W
i
d
t
h
cos sin
x AL
y d AW
x
h d d
= -
= + -
(δ)
Dislocation Theory

37. S is Slip For Oblique Slip
S= s.cos ψ + s.sin ψ
d= sG(m)
Relationship between dislocation field (d) and the
fault geometry G(m)
Dislocation Theory

38. Consider the case we have observed data d
1
, d
2
, ……. d
n

and the Green function of each observation data are G
1
, G
2
,
……. G
n
respectively, Then:
Suppose we have n GPS Stations
Dislocation Theory

39. Richter magnitude scale
The Richter magnitude scale (Richter scale)
assigns a magnitude number to quantify the
energy released by an earthquake.
Seismic moment = μ* slip*rupture area
M
O
= μ*s*A
M
O
= μ*s*L*W
μ = shear modulus of the crust (approx 3x10
10
N/m
2
)
L= Length of finite rectangular fault
W= Width of finite rectangular fault
s = slip

40. μ = 3x10
10
N/m
2
L=400 km
W= 50 km
s = 10 mm
M
O
= μsLW
Mo=(3x10
10
)x(10 x10
-3
)x (400 x 10
3
)x(50 x 10
3
)
Mo=(3x10
10
)x(10
-2
)x (2 x 10
5
)x(1x10
5
)
Mo=6x10
18
18
10
log (6 10 )
6.07
1.5
w
M Nm
´
= -
Richter magnitude scale

41. 18
10
10
log (6 10 )
6.07
1.5
log(6) 18log (10)
6.07
1.5
0.778+18
6.07
1.5
6.448
w
w
w
w
M
M
M
M Nm
´
= -
+
= -
= -
=
Richter magnitude scale