Download Science Unit 3

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Friday, November 13, 2009
Science Unit 3
Chapter 8
Section 8.2
I. Destruction From Earthquakes
A. Intensity of quake
B. Duration of Vibrations
C. Material of Foundations
1. Liquefaction
a. sinking effect (“Quicksand Phenomena”)
D. Design of the structure
II. Tsunami (uses a tsunami warning system)
A. Formation
1. Slab of the Ocean floor is displaced vertically along a
fault.
2. Vibrations from an Earthquake
a. Starts an underwater landslide
3. Landslides falling into an ocean
4. Fires
III. Predicting Earthquakes
A. NO way to predict
B. Tsunami’s have an Early Warning System
C. Seismographs give us maybe a few hours warning
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Friday, November 13, 2009
Science Unit 3
Chapter 8
Section 8.4
Earth’s Composition
I. Mantle (2890km)
A. Description
1. 82% Earth’s Volume
2. Solid, Rocky Layer
3. Upper Mantle
a. Periodite
II. Core
A. Solid
1. High pressure, high temperature
2. iron-nickel alloy
III. Layers by Composition
A. Physical Composition Classification
1. Temperature
2. Pressure
3. Density
B. Lithosphere (100km)
A. Crust and Uppermost Mantle
C. Asthenosphere
1. Known as the “Weak Layer”
2. Source of Magma
D. Mantle
1. Lower Mantle
a. Rigid
b. 660km
E. Core
1. Outer Core (2260km)
a. liquid
b. Generates Earth’s Magnetic Field
2. Inner Core (1220km)
a. Solid
i. extreme pressure overcomes temperature
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Friday, November 13, 2009
Science Unit 3
Chapter 9
Section 9.1
Continental Drift Theory
I. Supercontinent
- Theory continents once connected
A. Pangaea
1. Name of the “supercontinent” millions of years
ago
2. Developed by Alfred Wegener (German Scientist
1995)
# Reasoning/Evidence
1 Continents fit like puzzle pieces
Argument
a. Erosion could have
changed shorelines
2 Matching Fossils
a. Same Fossils on different
continents
a. Land Bridges are an
alternative…
b. No evidence under
oceans
N/A
3 Rock Types/Structures
a. mountains are the same age
w/similar rocks and structures
on different continents
4 Ancient Climates
N/A
a. Glacial deposits (220300mya)
- ice sheets covered large areas
of the southern hemisphere
II. Hypothesis Rejected
A. ø mechanism capable of movement
B. Wegener’s “mechanism”
1. The moon made the tides push and pull continents
2. The larger and sturdier continents literally broke
through the oceanic crust
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Friday, November 13, 2009
III. Post Wegener
A. In the following years strides were made:
1. mapping the ocean floor
2. earthquake activity
3. earth’s magnetic field
B. The theory of Plate Tectonics
1. Using the information above in 1968 the theory was
created
2. Basics for most geologic processes
IV. The Theory of Plate Tectonics
A. The lithosphere acts as a rigid layer sitting on a weaker
asthenosphere.
B. The asthenosphere is divided into plates which continually
change size and shape
C. 7 major plates:
1. Pacific
2. South American
3. Eurasian
4. Indo-Australian
5. African
6. Anartican
7. North American
Science Unit 3
Chapter 9
Section 9.2
Plate Tectonics
I. Types of Plate Boundaries
A. Divergent (a.k.a. spreading centers)
1. occurs when 2 plates move apart
2. create new sea floor
a. upwelling of material from the mantle. A relatively
new divergent boundary
B. Convergent
1. occurs where 2 plates mover together
2. oceanic lithosphere plunging beneath an overriding
plate
C. Transform Fault
1. where 2 plates grind past each other w/o production or
destruction of lithosphere.
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Friday, November 13, 2009
Science Unit 3
Chapter 9
Section 9.3
Actions at Plate Boundaries
I. Divergent Boundaries
A. location: along the crests of oceanic ridges
B. constructive plate margins
C. volcanoes
D. oceanic ridges
1. occur along well developed divergent plate boundaries
a. seafloor is elevated
2. rift valleys
a. deep faulted structures
E. seafloor spreading
1. the process of producing new oceanic lithosphere
a. typical rates of spreading average around 5cm/y
F. continental rift
1. spreading centers that develop within a continent
2. landmass split into 2 or more smaller segments
II. Convergent Boundaries
A. controlled by the type of crust and forces acting on the plate
B. subduction zones
1. occurs when one oceanic plate is forced down into the
mantle beneath a second plate
C. 3 Types:
1. Oceanic-Continental
a. continental volcanic arc
2. Oceanic-Oceanic
b. volcanic island arc
3. Continental-Continental
c. mountains
III. Transform Fault
A. mid-ocean ridge transform faults
1. @ every 100km along the ridge axis
a. active transform faults between the 2 offset ridge
segments
B. continental transform faults
2. San Andreas fault
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Friday, November 13, 2009
a. the Pacific is moving towards the N.W. past the
North Atlantic plate
Science Unit 3
Chapter 9
Section 9.4
Testing Plate Tectonics
# Evidence
1 Paleomagnetism
3 Ocean drilling
Reason/ Explanation
a. magnetic field
b. iron rich materials
1. heating
a. causes lots of magnetism
2. cooled
b. become magnetized in
the direction parallel to the existing
magnetic field
3. solid
a. keeps the magnetic
grains in the position of that magnetic
field
4. changes in Earth’s polarity
a. normal
b. reverse
c. strips of alternating polarity, which
lie as mirror images across the
ocean ridges, are among the
strongest evidence of seafloor
spreading
a. shallow-focus earthquakes occur
within or adjacent to the trench
b. intermediate- and deep-focus
earthquakes occur towards the
mainland
a. seafloor is not the same age
4 Hot spots
N/A
2 Earthquake patterns in and
around ocean trenches
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Friday, November 13, 2009
Science Unit 3
Chapter 9
Section 9.5
Mechanism of Plate Motion
I. Causes of Plate Movement
A. convection occurring in the mantle is the basic driving force
for plate movement
1. convective flow generated by unequal hear
a. radioactive decay of elements
B. Slab-pull and Ridge-push
1. slab-pull
a. downward arm of convective flow
2. ridge-push
a. oceanic lithosphere to slide down the sides of the
oceanic ridge