Theory of Plate Tectonics

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Plate Tectonics

• Plate Tectonics
• Plate Boundaries
• Causes of Plate Tectonics

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Plate Tectonics
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What is Plate Tectonics

• The Earths crust and upper mantle are broken
  into sections called plates
• Plates move around on top of the mantle like rafts

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What is the Lithosphere?

• The crust and part of the upper mantle
  lithosphere
• 100 km thick
• Less dense than the material below it so it
  floats

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What is the Asthenoshere?

• The plastic layer below the lithosphere
  asthenosphere
• The plates of the lithosphere float on the
  asthenosphere

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2 Types of Plates

• Ocean plates - plates below the oceans
• Continental plates - plates below the continents

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Questions...

• What is the theory of plate tectonics?
• What is the asthenosphere?
• What is the connection between the two?
• What are the two types of plates?

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Plate Boundaries
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Plate Boundaries

• Divergent Boundary moving
• Convergent Boundary moving
• Transform Fault Boundary moving
  ________________________

together
sideways past each other
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Divergent Boundaries

• Boundary between two plates that are moving apart
  or rifting
• ? ?
• RIFTING causes SEAFLOOR SPREADING

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Features of Divergent Boundaries

• Mid-ocean ridges
• rift valleys
• fissure volcanoes
• subduction zone called a TRENCH

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Convergent Boundaries

• Boundaries between two plates that are colliding
• ? ?
• There are 3 types

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Type 1

• Ocean plate colliding with a less dense
  continental plate
• Subduction Zone less dense plate slides under
  the more dense plate
• VOLCANOES occur at subduction zones

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Andes Mountains, South America
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Type 2

• Ocean plate colliding with another ocean plate
• VOLCANOES occur at subduction zones

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Aleutian Islands, Alaska
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Type 3

• A continental plate colliding with another
  continental plate
• Have Collision Zones
• mountains form.

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Transform Fault Boundaries

• Boundary between two plates that are sliding past
  each other
• EARTHQUAKES along faults

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San Andreas Fault, CA
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Questions...

• What are the three types of boundaries?
• What direction do plates go for each?
• Which boundary has a subduction zonewhat occurs
  at a subduction zone?

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Causes of Plate Tectonics
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What cause plates to move?

• Convection Currents
• Hot magma in the Earth moves toward the surface,
  cools, then sinks again.
• Creates convection currents beneath the plates
  that cause the plates to move.

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• The less dense plate slides under the more dense
  plate creating a subduction zone called a TRENCH

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• Subduction Zone where the less dense plate
  slides under the more dense plate
• VOLCANOES occur at subduction zones

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• Explain Pangaea

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• This is what type of boundary ?

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• What are the two types of plates?

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• Divergent plate boundaries move_______

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• Tectonic plates move only _______ per year
• Kilometers
• Miles
• Centimeters
• Millimeters

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• This type of plate movement can result in the
  formation of mountains and/or volcanoes

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• What is the lithosphere?

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• Two transformative plates slide past each other.
  What geological event is likely to occur?

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Questions...

• How is a convection current formed?

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• What are the three types of plate boundaries?

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• What causes plates to move?