Plate Tectonics

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Plate Tectonics
Earths Deformation
UNIT 2
Earthquakes
Volcanoes
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Did you know???

• Iowa used to the bottom an ocean?
• Alaska was once a tropical island?
• The Sahara Desert was once covered with ice?
• Antarctica was once swampland?
• Glaciers in Australia?
• How could this be???

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Chapter 4
Movement over 225 ? million years
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Continental Drift
Shorelines seem to fit!

• 1912 Alfred Wegener
• Continental Drift Theory
• Pangaea land
• Panthalassa ocean
• Evidence included
• Fossils
• Rock formations
• Climate migration
• Strong opposition
• Died in 1930 in Greenland on a quest to discover
  how the continents moved he never found the
  cause

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What powers all this motion?
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The secret of the ocean floor

• Plowing through ocean floor?
• Ocean floor was mapped for the 1st time in 1940s
• Ocean rocks were found to be younger than land
  rocks
• Rocks get younger as you move further into the
  ocean
• Constant renewal of ocean floor
• Mid-Ocean Ridge (Mid-Atlantic Ridge)
• Paleomagnetism - study of ancient Earth magnetism
• Theory of Seafloor Spreading

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Paleomagnetism
What does it tell us?
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The Birth of a Theory
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C Theory of Plate Tectonics

• Combines the two theories together (A B C)
• Where
• A Theory Continental Drift
• B Theory of Seafloor Spreading
• C explains the how and why of crustal
  movement
• Tectonics means construction or building
• Two types of crust
• Continental
• Oceanic
• Lithosphere (crust/upper mantle)
• Asthenosphere fluid solid

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Causes of Plate Motion

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Lithospheric Plate Boundaries
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3 Types of Boundaries
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Divergent Boundaries

• Pulling apart
• Mid ocean ridges
• Rift valleys
• Red Sea
• Mississippi River
• Volcanoes
• Fissures (rifting)

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Convergent Boundaries

• Crashing together
• Subduction zone
• Mountains
• Volcanoes
• Ocean trenches
• Earthquakes
• 3 main types

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Ocean Continental(Convergent)
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Continental Continental(Convergent)
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Ocean Ocean(Convergent)
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Transform (or Sliding)Boundaries

• Sliding
• Opposite directions or one going faster in same
  direction
• EARTHQUAKES!!!
• Do not slide smoothly
• Buildup of friction causes different strengths of
  earthquakes

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General Location of the 3 Boundary Types