earth’s structure and composition what is geology? what are the characteristics of earth’s three...
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Earth’s Structure and Composition
•What is geology?
•What are the characteristics of Earth’s three layers?
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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
Geology = The study of the planet Earth’s composition & structure
Seimic waves & E’s interior:http://www.classzone.com/books/earth_science/terc/content/investigations/es0402/es0402page01.cfm
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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
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Earth: Cross SectionMajor Layers1. Core (inner and outer)2. Mantle3. 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)
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Core Mantle Crust
Iron (85%)
Nickel (11%)
Sulfur (4%)
Density: ~11 g/cm3
Density: ~5 g/cm3
Density: ~3 g/cm3
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The Composition of the Earth
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CrustTypes 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)
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Abundances of Elements in Earth’s
Crust
Silicon & Oxygen compounds = silicates
( ~ 74%)
These make crust light!
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“Moho” =
boundary b/w crust & upper mantle
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Mantle Convection
http://www.see.leeds.ac.uk/structure/dynamicearth/convection/index.htm
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The MantleComposition: 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
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3 Divisions of the Mantle
Lithosphere = Upper mantle + Crust“Plates”, Rigid Slabs
Asthenosphere = Softer, moving hot rock (Convection Currents)
Mesosphere = Stiffer rock near core
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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
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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)
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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
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Visualizations • 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/movies-more.html
• Mantle Convection: http://www.youtube.com/watch?v=p0dWF_3PYh4&feature=results_main&playnext=1&list=PL8873B6173CE6E948
• 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=23uwKo6vd0Y&feature=related• 2012 mag reversal:• http://www.youtube.com/watch?
v=zOk7_6pcUns
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=ZP9R20QgDNs&feature=related
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Iron (85%)
Nickel (11%)
Sulfur (4%)
Density: ~11 g/cm3
The Core
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Label Each Layer.
Be able to describe each layer.
Upper mantle
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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?
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Answers to Self Quiz
1. Constructive forces build new land/crust and destructive forces destroy crust.
2. Crust, Mantle, Core3. The asthenosphere – which is in the mantle4. The core5. The crust5. Oceanic crust is denser (but thinner)6. The upper mantle (and the crust make up the
lithosphere, or plates)7. Core