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• Plate tectonics (pp 339-343)• Plate boundaries (pp 343-348)• Earthquakes (pp 375-384)
Wednesday July 11
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Free floating magnetite particles align following a well defined pattern around a magnet.If support is frozen, and magnet is moved, magnetite particles keep trace of the old position of the magnet
Magnetic poles drift?
Yes, but not possible to have two north poles!!!
Plate tectonics is the explanation!!
Evidences of plate tectonics
1) Shape of continents
2) Magnetic pole drift
3) Hot spots
4) Magnetic striping and age of seabed
5) Similarities in fauna and flora
Evidences of plate tectonics
1) Shape of continents
2) Magnetic pole drift
3) Hot spots
4) Magnetic striping and age of seabed
5) Similarities in fauna and flora
Evidences of plate tectonics
1) Shape of continents
2) Magnetic pole drift
3) Hot spots
4) Magnetic striping and age of seabed
5) Similarities in fauna and flora
Plate motion and
boundaries
Why do plates move??
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PLATE MOTIONThree types of plate boundary
Divergent boundary
Animation 1
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Example: Mid-Atlantic
Ridge
•a topographically high area near the middle of the Atlantic Ocean
•splits nearly the entire Atlantic Ocean north to south,
Divergent: Atlantic Ridge
LAVA FOUNTAINSKRAFLA VOLCANOICELAND
Rio Grande Rift
Animation 2
Convergent boundary I:oceanic -continental plate involved ->
Subduction
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OCEANIC-CONTINENTAL COLLISONS SUSTAIN MOSTVOLCANIC ACTIVITY AROUND THE PACIFIC OCEAN
Convergent boundary II:oceanic -oceanic plates involved ->
SubductionSubduction processes in oceanic-oceanic
plate convergence result in the
formation of volcanic arc islands
Animation 3
Convergent boundary III:NO oceanic plate(s) involved -> Mountain
chains
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Convergent boundary III:NO oceanic plate(s) involved -> Mountain
chains
Example: Andes Mtns
West margin of the South American continent
•oceanic Nazca Plate is pushed toward and beneath the continental portion of the South American Plate
•typical example of a convergent plate boundary
Nazca - S.America plate collision
Transform boundary
Animation 4
Transform boundary
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Example:San Andreas fault in California
Pacific Plate slides past the North American Plate.
Transform boundary
Plate Motion Summary
Earthquakes
• Are due to the release of strain in the lithosphere
• They propagate as waves of two types:
• Compression (or longitudinal or P-mode) waves
• Deformation (or transversal or S-mode) waves