Plate Tectonics

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Plate Tectonics
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The Theory Of Plate Tectonics States

• The Lithosphere is divided into ten major plates
  and a number of smaller plates.

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Global Picture Of the Earths Tectonic Plates
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• Plates are in constant motion and are continually
  changing shape and size.

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• Most of the Earths Volcanoes, Earthquakes and
  Mountain Ranges occur along Plate Boundaries!

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• There are three types of plate boundaries
• Divergent Boundaries
• Convergent Boundaries
• Transform Boundaries

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Divergent boundaries

• Plates moves apart
• New crust is created as hot magma rises up from
  the mantle.
• Mountains associated with divergent boundaries
  are called ridges.

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Divergent Boundary
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Examples of Divergent Boundaries Mid-Atlantic
Ocean Ridge, East African Rift, and Red Sea
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Spreading Centers
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East Africa Rift and Red Sea
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Convergent Boundaries

• Plates move toward each other and collide.
• There are three types of convergent boundaries.
• Collisions between two oceanic plates
• Collisions between two continental plates
• Collisions between a continental and oceanic
  plate.

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Convergent Boundary
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Collisions Between Two Oceanic Plates

• Sinking crust melts in the mantle. The less
  dense magma created from the melted crust rises
  up through the crust forming a chain of volcanic
  islands called island arcs.
• Where one plate sinks underneath another plate is
  called a subduction zone.
• Examples
• Japanese and Philippines Islands

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Mt. Pinatubo
Mt Unzen
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Collision Between Two Continental Plates

• Neither plate sinks because continental plates
  are light and buoyant.
• As the plates collide they buckle and form huge
  mountain ranges and plateaus.
• Examples
• Alps, Himalayas, Tibetan Plateau

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India Is still moving into Asia Today
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Himalayas
India Today
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Himalayas
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Collision between A Continental Plate and an
Oceanic Plate

• The heavier oceanic plate will sink under the
  lighter continental plate.
• The convergence causes the continental plate to
  buckle up forming mountains.
• As the heavier oceanic plate subducts it melts in
  the mantle and hot magma rises up forming
  volcanoes called a Volcanic Arc on the
  continental plate.
• Examples
• Mt. St. Helens and Lassen Peak in the Cascade
  Mountain Range and the Andes Mountains

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Continental and Oceanic Crust Collision
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Mt. St. Helens
Lassen peak
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Transform Boundaries

• At transform boundaries plates slide past each
  other.
• Crust is neither being destroyed nor created.
• Transform boundaries join segments of ridge
  systems on the ocean floor.
• Transform boundaries join segments of converging
  and diverging boundaries.
• Examples
• San Andreas Fault

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Transform Boundary
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San Andreas Fault System And Attached Ridges
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San Andreas Fault System
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Identify the Plate Boundaries below A. B.
C. D. E.
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Section 3 The Theory of Plate Tectonics
Causes of Tectonic Plate Motion
Click below to watch the Visual Concept.
Visual Concept
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Section 3 The Theory of Plate Tectonics
Possible Causes of Tectonic Plate Motion

• What causes the motion of tectonic plates? This
  movement occurs because of changes in the density
  within the asthenosphere.
• The following Visual Concept presentation
  examines three possible driving forces of
  tectonic plate motion.

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Section 3 The Theory of Plate Tectonics
Tracking Tectonic Plate Motion

• Tectonic plate movements are so slow and gradual
  that you cant see or feel them. The movement is
  measured in centimeters per year.
• Scientists use a system of satellites called the
  global positioning system (GPS) to measure the
  rate of tectonic plate movement.

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Section 3 The Theory of Plate Tectonics
Newtons Second Law of Motion, continued
Click below to watch the Visual Concept
Visual Concept