Post on 12-Jan-2016
transcript
Earth’s Structure and Composition
•What is geology?
•What are the characteristics of Earth’s three layers?
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
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 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)
Core Mantle Crust
Iron (85%)
Nickel (11%)
Sulfur (4%)
Density: ~11 g/cm3
Density: ~5 g/cm3
Density: ~3 g/cm3
The Composition of the Earth
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)
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 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
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 • 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
Iron (85%)
Nickel (11%)
Sulfur (4%)
Density: ~11 g/cm3
The Core
Label Each Layer.
Be able to describe each layer.
Upper mantle
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, 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