Chapter 13 Plate Tectonics

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• Chapter 13 Plate Tectonics
• Topic 1 Moving Plates Cover the Globe
• Earths surface is similar to a cracked egg
  shell. The very thin outer shell of the egg
  represents the crust (lithosphere) of earth.

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• Earths surface consists of solid, moving plates.
• 12 major plates consist of the continental and
  the oceanic crust. Some plates have both.
• Topic 2 How Thick are the Plates?
• Lithosphere very thin 100 km thick
• Continental rock (granitic) is lighter, less
  dense than oceanic rock (basaltic) therefore,
  the continents ride up higher on the surface of
  earth

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• The crust and the upper most part of the mantle
  is called the lithosphere (same composition and
  physical properties)
• The lithosphere is the layer of solid rock that
  is broken up into the 12 major plates.
• The lithosphere rests on the asthenosphere
  (mantle) which is like silly putty partially
  melted.

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• Topic 3 Why Do the Plates Move?
• Convection currents are thought to be responsible
  in moving the plates. As hot magma rises to the
  surface it cools and becomes more dense and then
  sinks.

Convection Currents in mantle
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• Some plates are moving towards each other (
  Indian Plate colliding into the Eurasian Plate)
• Some plates are moving away from each other
  (South American Plate and the African Plate)
• Some are sliding past each other - Pacific and N.
  American

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Three types of Movement

• Divergent boundaries-moving away from each other.
• Convergent boundaries-moving toward each other
• a. 2 continental plates
• b. Continental and oceanic plate
• 3. Lateral or strike-slip - move parallel

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Plates move apart where convection currents are
bringing magma to surface. Plates move together
when cooler, denser currents within the
asthenosphere are sinking.
Or when two lithospheric plates move together.
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• Topic 4 Evidence for Plate Tectonics
• The 1800s brought the first reliable world maps.
  
• In 1912 Alfred Wegner first proposed his theory
  of Continental Drift -
• Evidence was
• 1) Jig-saw puzzle fit of continents from newly
  published maps

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Pangaea all land
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Other Evidence 2) Fossil remains Mesosaurus
and others 3) Similar rock types and ages on two
different continents
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5) Climatic patterns evidence of glaciation on
tropical continents. Also coal deposits in East
Coast of US.
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• http//visearth.ucsd.edu/VisE_Int/aralsea/bigone.h
  tml

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Evidence for Continental Drift and Sea Floor
Spreading Age of Rocks and Magnetism

• Rocks next to the midoceanic ridge are younger
  than rocks further away from ridge.
• Identical magnetic strips on either side of ridge.