1. Earth’s Layered Structure

2. The story so far…… Evidence of Earth’s Layers and their composition
PHENOMENON:
What did you observe?
What evidence do you have?
OBJECTS:
Define the system.
What objects are interacting?
MOTION:
Describe the motion that in the model that explains your observations
Rocks of Earth’s crust vary in density: granite is less dense, then basalt, peridotite and iron  
Molten lava erupts from volcanoes.  
Mohorovic found that EQ wave velocities change at about 50 km.
  EQ P waves are reflected, bent, velocity decreases and S-waves are stopped.
  Earth has a north and south magnetic pole.
Temperature, density and velocity changes at certain depths: (100 km, 1000 km, 3000 km, 5000 km)  
  Ave. density of the crustal rocks ; granite, basalt, peridotite is 3.0 g/cc. Yet the average density of the entire Earth is 5.4 g/cc
Meteorites formed from the same materials at the same time as the terrestrial planets. Some of them are rocky and some are metallic
EQ waves were found to reflect, bounce off “something” solid in the center
EARTH’S CRUST is made of rocky material got “sorted” by density when Earth was a young molten planet. More dense iron sank to center and less dense basalt and granite are on top.
Magma suggests that there is liquid, MANTLE of molten rock under the solid, rocky crust
There is a boundary between the solid crust and the liquid (magma) mantle layer.
Earth has an OUTER CORE composed of liquid IRON that is flowing creates a magnetic field.
The Earth’s INNER CORE must be very dense metal (iron 7.9 g/cc and nickel 8.9 g/cc) to average out to 5.4 g/cc
The inner core is SOLID iron and nickel
Density of Earth’s Rocks Lab
Magma video clip
Earthquake P and S waves
Compass, magnets
Rock Lab data
Meteorite samples

4. So….Earth’s 4 layers were determined by physical properties….
Temperatures and pressures
(both increase and change with greater depth)
Physical properties
(density, chemicals and elements)
3. Mechanical behavior
(how the material moves or doesn’t move: solid or liquid)

5. Earth’s Main Layers Lithosphere/crust Mantle Outer Core Inner Core

7. Crust / Lithosphere (pg. 72)
“litho-” stone, “-sphere” circle
Contains the crust and upper mantle
Relatively cool
Rigid, brittle, shell
Depth
Ave. 100 km or 60 miles

8. Continental Crust Cold, brittle, fractures (earthquakes)
Averages km (25 miles ) thick
Can exceed 70 km (40 mi) in mountains!
Rock types:
Upper crust is mostly light, silicate rocks such as granite rock
Up to 4 billion years old!
2.7 g/ml density

9. Oceanic Crust 7 km (5 miles ) THIN Composed of dark, igneous rock
Basalt (black, ocean basin)
180 million years young
(or less)
3.0 g/ml density

10. Re-melted, destroyed, recycled
Two distinct types of crust
Continental Crust
Characteristic
Oceanic Crust
35-50 km
Thickness
5-12 km
Granite (light)
Composition
Basalt (dark)
to 3.8 billion yrs.
Geological age
to 150 million yrs
2.7
Density
3.0
Ave. +1,000 m
Elevation
Ave. - 3,000 m No
Re-melted, destroyed, recycled
Yes
Deformed
33%
Current distribution
67%
*Origin of continental crust is the partial re-melting of original oceanic crust

11. Asthenosphere (asthenos- weak)
upper mantle
100 km to 660 km
Soft, solid/liquid,
weak in structure,
constantly moving

12. Interaction between lithosphere and asthenosphere
But the lithosphere sits “floats” on top of the asthenosphere.
Lithosphere (land) gets moved
(like a person being moved on an escalator)

14. Mantle The region that lies between the crust and the outer core
Thickest of the Earth’s layers
Over 70% of Earth’s volume
Down to 2900 km (1800 miles)
Mostly solid, but…
High temps. and pressure cause it
to behave in a plastic (putty) manner.
(like thick, hot asphalt)

15. Volcanic MAGMA comes from the mantle

16. Most of the Earth's mass is in the mantle is composed of what 5 elements?
silicon (Si)
2. oxygen (O2)
3. Magnesium (Mg)
4. Aluminum (Al)
5. Iron (Fe)

17. Outer Core molten (liquid) IRON and nickel (alloy)
MOVES / FLOWS like a liquid
about 10% sulfur (S)
Density: 11 g/cm3
Convective flow of the liquid magnetic iron causes the Earth’s magnetic field

18. Inner Core Radius 1216 km (754 miles) size of our moon
Mostly IRON (Fe)
Spins?
Extremely high temperature (+3700°C or 6700°F)
Yet it doesn’t melt, it’s Solid!
Immense pressure of the overlying layers prevent the iron from melting.
Average density of 14 g/cm3

19. Earth’s Layers Solid Liquid Pressure Temp. Crust Mantle Outer Core
(check)
Liquid
Pressure
Most-least
Temp.
Crust
Mantle
Outer
Core
Inner X
X X 3 3 X
X most most

20. Earth’s Layers Review Name that layer!
1.________: Solid iron and nickel most dense; highest temperature due to intense pressure
2. ________: Liquid iron and nickel, flows to produce Earth’s magnetic field
3._________: Most 70% (thickest layer)-Compounds rich in iron, silicon, magnesium, olivene, peridotite; molten magma originates here
4.________: Rigid layer of lighter rocks
5. ________________: Crust and uppermost mantle
6. ________________: Lithosphere floats on a thin, slush-like layer of the mantle (UPPER MANTLE). Lava lamp

21. Answers
1.________: Solid iron and nickel most dense; highest temperature due to intense pressure
2. ________: Liquid iron and nickel, flows to produce Earth’s magnetic field
3._________: Most 70% (thickest layer)-Compounds rich in iron, silicon, magnesium, olivene, peridotite; molten magma originates here
4.________: Rigid layer of lighter rocks
5. ________________: Crust and uppermost mantle
6. ________________: Lithosphere floats on a thin, slush-like layer of the mantle (UPPER MANTLE). Lava lamp
Inner Core
Outer Core
Mantle
Crust
Lithosphere
Asthenosphere