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

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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

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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 QuickTime™ and a Cinepak decompressor are needed to see this picture.

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