Transcript Chapter 22.1: Earth`s Structure

Earth’s Structure and Composition
•What is geology?
•What are the characteristics of
Earth’s three layers?
Geology = The study of the planet Earth’s
composition & structure
Seimic waves & E’s interior:
http://www.classzone.com/books/earth_science/terc/co
ntent/investigations/es0402/es0402page01.cfm
How do we know about Earth’s interior if
we can’t see it?
- Interpret seismic (earthquake) waves
- Waves travel at different speeds in
different mediums and materials
2 Forces that Change Earth’s
Surface
A. Constructive Forces =
Forces that build up mountains etc.
B. Destructive Forces =
Forces that slowly wear away any feature
Earth: Cross Section
Major Layers
1. Core (inner and outer)
2. Mantle
3. Crust
- Why does Earth have layers?
Most dense material sinks to center / Light
stuff “floats” on top
- Temperature and pressure
increase with depth.
Temps: Inner core (13 000 F = surface of
sun); Mantle (Range fr. 7 000 – 1 600F)
- Each layer varies in physical
properties: density, temp., ability to
flow (viscosity)
Core
Mantle
Crust
Sulfur (4%)
Nickel
(11%)
Iron (85%)
Density:
~11 g/cm3
Density: ~5
g/cm3
Density: ~3
g/cm3
The Composition of
the Earth
Crust
Types of Crust
A. Continental
• Less dense rocks like
granite
• 8 – 40 km thick
• Older
B. Oceanic
• Dense rocks like
basalt
• ~7 km thick
• Younger
Composition
•Light Rock layer
• Thin layer
• Made of silicates
(Light rocks of silicon &
oxygen)
Abundances of
Elements in Earth’s
Crust
Silicon & Oxygen
compounds = silicates
( ~ 74%)
These make
crust light!
“Moho” =
boundary
b/w crust &
upper mantle
Mantle Convection
http://www.see.leeds.ac.uk/structure/dynamicearth/convection/index.htm
The Mantle
Composition: Hot Heavy
Rock!
Made of silicates; but also a lot of
iron & magnesium (heavier)
• Temps: 1,600  7,000 F
• Pressure increases as you
descend!
Not COMPLETELY solid
• Middle part is “plastic”/ taffy
like
• Hot rock moves in
CONVECTION CURRENTS
3 Divisions of the Mantle
Lithosphere = Upper
mantle + Crust
“Plates”, Rigid Slabs
Asthenosphere = Softer,
moving hot rock
(Convection Currents)
Mesosphere = Stiffer
rock near core
How do we know what’s in the
mantle?
How do we know what it is
made of?
• Scientists infer based
on:
• Pushed up rock
• Ocean floor/molten
rock
• Seismic waves
What is it like?
• Like the mineral olivine
• Large amounts of
iron and
magnesium
Core
• Composition: Heavy Metals!
• Iron & Nickel
(How do we know? Earth’s
magnetic field & seismic waves)
• Pressure 3.6 million times that at
surface
• Temps: 6 700 C (same as
surface of sun)
2 Layers of Core
• Inner Core
– Solid iron and nickel
– High pressure keeps
it solid
Outer Core
• Liquid iron and nickel
• High temp. keeps it liquid
• Responsible for Earth’s
magnetic field
Visualizations
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Earth Science Classzone:
http://www.classzone.com/books/earth_science/terc
/navigation/investigation.cfm
Visuals on plate convection:
http://www.gps.caltech.edu/~gurnis/Movies/mov
ies-more.html
Mantle Convection:
http://www.youtube.com/watch?v=p0dWF_3PYh
4&feature=results_main&playnext=1&list=PL887
3B6173CE6E948
Pole Reversal:
http://www.youtube.com/watch?v=x-p49IBuR1Y
Polar Shift
http://www.youtube.com/watch?v=akBvr_ZUCro
&feature=related
Polar Shift 2012:
http://www.youtube.com/watch?v=23uwKo6vd0
Y&feature=related
2012 mag reversal:
http://www.youtube.com/watch?v=zOk7_6pcUn
s
Early Earth & Plate Tectonics:
http://www.youtube.com/watch?v=QDqskltCixA&
feature=related
Journey to the center of the Earth
Part 1:
http://www.youtube.com/watch?v=kibQWhiymtM
Part 6: 4 min.- mineralogy & seismo.
http://www.youtube.com/watch?v=XYbE5jA0plA
Part 7: Seismic waves
http://www.youtube.com/watch?v=ZP9R20QgDN
s&feature=related
The Core
Sulfur (4%)
Nickel
(11%)
Iron (85%)
Density:
~11 g/cm3
Upper mantle
Label Each Layer.
Be able to describe each layer.
Self Quiz
1. Compare how constructive and destructive
forces affect Earth’s surface.
2. List the 3 layers of Earth.
3. Which layer has currents of moving rock?
4. Which is the most dense layer?
5. Which layer is made of light rocks like silicates?
6. Which is more dense: Continental or Oceanic
Crust?
7. Which layer of the mantle is part of Earth’s
plates?
8. Which layer is made of heavy metals?
Answers to Self Quiz
1. Constructive forces build new land/crust and
destructive forces destroy crust.
2. Crust, Mantle, Core
3. The asthenosphere – which is in the mantle
4. The core
5. The crust
5. Oceanic crust is denser (but thinner)
6. The upper mantle (and the crust make up the
lithosphere, or plates)
7. Core