interior structure of the earth
TRANSCRIPT
•The Earth's mass is about 5.98 x 1024 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
CrustMantle Core
The Earth is divided into three main layers.
Earth Layers
Shell = crustEgg white = mantleYolk = core
How are the earth’slayers similar to anegg?
Earth Layers
Earth LayersCrust = 0 to 50 kmMantle= 50 to 2900 kmOuter Core= 2900 to 5100 kmInner Core= 5100 to 6371 km
Earth Layers
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.
CrustCrust
•Thinnest layer (0-50 km)•Two types of crust
Continental crustOceanic crust
The Crust
ContinentalAverage 30 km
OceanicAverage 5-8 km
The Crust
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.
•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
The Core
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
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
Plate Tectonics
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.
• Plates are made of rigid lithosphere.
• The lithosphere is made up of the crust and the upper part of the mantle.
Plate Tectonics
Plate Tectonics
• Below the lithosphere which makes up the tectonic plates is the asthenosphere.
• “Plates” of lithosphere are moved around by the underlying hot mantle convection cells
Plate Tectonics
The lithosphere is broken up into plates that move horizontally across the Earth.
Earth’s Layered Structure
• Divergent
• Convergent
• Transform
Three types of plate boundary
Plate BoundariesConvergent
• Ocean-continent
• Ocean-ocean
• Continent-continent
Plates move away from each other
Plate BoundariesDivergent
• Plates move away from each other• New crust is being formed
Plate BoundariesTransform
• Plates slide past one another
• Crust is neither created nor destroyed
• 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…
Length
Wid
th
DIP Angle
Slip
FaultRake 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
Top Depth
LengthWid
th
Bottom DepthEarth Surface
( ) Bottom Depth Top DepthSin Dip AngleWidth
Fault
Strike-Slip Fault
• The movement of blocks along a fault is horizontal.
•Rake zero (0o ) Slip
•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
Dip-Slip Fault
• The movement of blocks along a fault is vertical.
•Rake (90o )
Slip
•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 450 is called Thrust Fault.
Dip-Slip Fault
Normal Fault
Thrust Fault
Reverse Fault
Dip-Slip Fault
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
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 Len
gth
Wid
th
DIP
Slip
Length(AL) Wid
th(A
W)
LengthW
idt
h
cos sinx ALy d AW
(δ)
Dislocation Theory
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
Consider the case we have observed data d1, d2, ……. dn and the Green function of each observation data are G1, G2, ……. Gn respectively, Then:
Suppose we have n GPS Stations
Dislocation Theory
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 MO= μ*s*A
MO= μ*s*L*Wμ = shear modulus of the crust (approx 3x1010 N/m2)L= Length of finite rectangular faultW= Width of finite rectangular faults = slip
μ = 3x1010 N/m2
L=400 kmW= 50 kms = 10 mmMO= μsLWMo=(3x1010 )x(10 x10-3 )x (400 x 103 )x(50 x 103 )Mo=(3x1010 )x(10-2 )x (2 x 105)x(1x105 )Mo=6x1018
1810log (6 10 ) 6.07
1.5wM Nm
Richter magnitude scale
1810
10
log (6 10 ) 6.071.5
log(6) 18log (10) 6.071.5
0.778+18 6.071.5
6.448
w
w
w
w
M
M
M
M Nm
Richter magnitude scale