Plate Tectonics part III

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Plate Tectonics (part III)
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Plate Tectonics

• A modern version of an old idea
• Product of the merging of two earlier ideas
• Continental drift early 1900s
• Sea-floor spreading early 1960s
• Was widely accepted even in other scientific
  fields (i.e. Physics, Biology)

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• The problem of ploughing of continental crust
  into oceanic crusting was solved.
• In plate tectonics, both continental crust and
  oceanic crust can move together.

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• There was a mechanism for moving the continents,
  which the continental drift theory did not
  satisfy.

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• Most importantly, magnetism, a field of study in
  Physics, was the convincing proof for the plate
  tectonics theory.

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• Plate Tectonics provided a mechanism to explain
  the distribution of present-day organisms

• Modern organisms with similar ancestries had to
  evolve in isolation during the last few tens of
  millions of years
• Australian marsupials (e.g. Kangaroos) and South
  American marsupial opposums.

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• Explains the strange behavior of animals

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• Wide acceptance by the scientific community
• Alfred Wegener was vindicated

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A triumph of the human mind and spirit !!!
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Plate Boundaries
Insert picture of plates
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Plate Boundaries

• A. Divergent
• B. Convergent
• C. Transform-
• Fault

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A. Divergent plate
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B. Convergent plate

• Oceanic-Continental convergence

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B. Convergent plate

• 2. Oceanic-Oceanic convergence

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B. Convergent plate

• 3. Continental-Continental convergence

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C. Transform-Fault
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Transform-Fault
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Testing the model

• Earthquakes along plate boundaries
• Evidence from ocean drilling
• Hot spots
• Direct measurements from Global Positioning
  Systems

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• Earthquakes occur in plate margins

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Shallow, intermediate and deep focus earthquakes
define subduction zones (Benioff Zone)
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The pile of sediments get thicker farther away
from the oceanic ridge
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Hot Spots a concentration of heat in the mantle
capable of producing
magma which, in turn, extrudes onto the Earths
surface
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Global Positioning Systems (GPS) measured
movement is 1-10 cm per year
Insert picture of GPS
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The Driving Mechanism?!
Convection cells that move the lithosphere in a
conveyor-like fashion
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end