Download Plate tectonics

Wednesday July 11
• Plate tectonics (pp 339-343)
• Plate boundaries (pp 343-348)
• Earthquakes (pp 375-384)
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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)
2)
3)
4)
5)
Shape of continents
Magnetic pole drift
Hot spots
Magnetic striping and age of seabed
Similarities in fauna and flora
Evidences of plate tectonics
1)
2)
3)
4)
5)
Shape of continents
Magnetic pole drift
Hot spots
Magnetic striping and age of seabed
Similarities in fauna and flora
Evidences of plate tectonics
1)
2)
3)
4)
5)
Shape of continents
Magnetic pole drift
Hot spots
Magnetic striping and age of seabed
Similarities in fauna and flora
Plate motion
and boundaries
Why do plates move??
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PLATE MOTION
Three 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 FOUNTAINS
KRAFLA VOLCANO
ICELAND
Rio
Grande
Rift
Convergent boundary I:
oceanic -continental plate involved ->
Subduction
Animation 2
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OCEANIC-CONTINENTAL COLLISONS SUSTAIN MOST
VOLCANIC ACTIVITY AROUND THE PACIFIC OCEAN
Convergent boundary II:
oceanic -oceanic plates involved -> Subduction
Subduction processes in oceanicoceanic
plate convergence result in the
formation of volcanic arc islands
Convergent boundary III:
NO oceanic plate(s) involved -> Mountain chains
Animation 3
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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
Transform boundary
Animation 4
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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 Pmode) waves
• Deformation (or transversal or S-mode)
waves