PLATE TECTONICS Chapter 10

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PLATE TECTONICSChapter 10

• Section 2
• The Theory of Plate Tectonics
• (pages 247-253)

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CONTINENTAL DRIFTanimation

• http//www.classzone.com/books/earth_science/terc/
  content/visualizations/es0806/es0806page01.cfm?cha
  pter_novisualization

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FUTURE PLATE MOTIONS animation

• http//www.classzone.com/books/earth_science/terc/
  content/visualizations/es0807/es0807page01.cfm?cha
  pter_novisualization

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SEA FLOOR SPREADING animation

• http//www.classzone.com/books/earth_science/terc/
  content/visualizations/es0803/es0803page01.cfm?cha
  pter_novisualization

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The THEORY of PLATE TECTONICS

• Plate tectonics is the theory that explains
• WHY HOW CONTINENTS MOVE the
• FORMATION of FEATURES (mountains oceans)

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INTERIOR LAYERS of the EARTH

• LITH means
• ROCK, so the LITHOSPHERE is the
• SPHERE of ROCK
• The LITHOSPHERE is made of..
• EARTHs CRUST and
• the RIGID UPPER part of the MANTLE
• (The outer rocky parts of Earth!)

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INTERIOR LAYERS of the EARTH

• Since ASTHEN means WEAK,
• ASTHENOSPHERE must mean
• 
  WEAK SPHERE
• The ASTHENOSPHERE is
• A layer of PLASTIC ROCK just below lithosphere
• PLASTIC ROCK is
• SOLID ROCK that is UNDER GREAT PRESSURE,
• so it FLOWS SLOWLY like THICK PUTTY

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TECTONIC PLATES

• The tectonic plates are made of _______ (sphere)
• 
  LITHOSPHERE
• which is floating on top of _______ (sphere)
• 
  ASTHENOSPHERE
• How many MAJOR tectonic plates have been
  identified by scientists?
• 
  15

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TYPES of CRUST

• Earth has two types of crust
• 1) OCEANIC CRUST
• 2) CONTINENTAL CRUST
• _____________crust is LOW density
• CONTINTENTAL
• _____________crust is HIGH density
• OCEANIC

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TYPES of CRUST

• How will you remember that oceanic crust is more
  dense than continental crust?
• Think of smashing something soft so it becomes
  smaller and more dense as it would under
  thousands of pounds of ocean!

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TECTONIC PLATES

• Which kind of crust are tectonic plates made of?
• BOTH
• Are rifts always between continents?
• NO, plate boundaries do not always match the
  outlines of the continents

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EARTHQUAKES VOLCANOES(chapter 12 chapter 13)

• EARTHQUAKES are
• SUDDEN SHIFTS ALONG PLATE BOUNDARIES
• Some VOLCANOES form when
• PLATE MOTIONS GENERATE MAGMA THAT ERUPTS ON
  EARTHS SURFACE for example
• The PACIFIC RING of FIRE

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TYPES of PLATE BOUNDARIES

• There are 3 types of plate boundaries
• DIVERGENT BOUNDARIES
• CONVERGENT BOUNDARIES
• TRANSFORM BOUNDARIES

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PLATE BOUNDRY MOVEMENTSanimation

• http//www.classzone.com/books/earth_science/terc/
  content/visualizations/es0804/es0804page01.cfm?cha
  pter_novisualization

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DIVERGENT BOUNDARY

• a DIVERGENT BOUNDARY is where 2 plates DIVERGE
  or MOVE AWAY FROM EACH OTHER
• An example of a divergent boundary is
• a RIFT VALLEY such as one filled by the RED SEA
• between the Arabian plate to the ______
• 
  EAST
• and the African plate to the _____
• 
  WEST

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DIVERGENT BOUNDARY

• a RIFT VALLEY is
• A NARROW VALLEY THAT FORMS WHERE TECTONIC PLATES
  ARE SEPARATING
• A rift valley can be found running down the
  center of a ___-______ _____
• MID-OCEAN RIDGE

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CONVERGENT BOUNDARY

• a CONVERGENT BOUNDARY is where 2 plates
• COLLIDE
• With 2 types of crust ___ collisions are
  possible.
• 3
• Continental crust hits oceanic crust
• Continental crust hits continental crust
• Oceanic crust hits oceanic crust

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1) CONTINTENTAL vs. OCEANIC

• The word for SINKING UNDER is
• 
  SUBDUCT
• When oceanic crust converges with continental
  crust which one SUBDUCTS?
• OCEANIC CRUST SINKS UNDER CONTINENTAL
• WHY?
• OCEANIC CRUST IS MORE DENSE

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1) CONTINTENTAL vs. OCEANIC

• As the oceanic crust subducts below the
  continental crust the oceanic crust is
• heated and squeezed into
• magma which rises to form
• VOLCANIC MOUNTAINS

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CONVERGENCE between OCEANIC CONTINENTAL
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2) CONTINENTAL vs. CONTINTENTAL

• When continental converges with continental crust
  WHICH ONE SUBDUCTS?
• NEITHER ONE
• So, what cant go down must go _____
• 
  UP
• to form_________________.
• MOUNTAINS

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CONVERGENCE between CONTINENTAL CONTINENTAL
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FORMATION of the HIMALAYAS animation

• http//www.classzone.com/books/earth_science/terc/
  content/visualizations/es1105/es1105page01.cfm?cha
  pter_novisualization

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3) OCEANIC vs. OCEANIC

• When oceanic crust converges with oceanic crust
  what forms?
• One subducts forming a DEEP OCEAN TRENCH
• Then fluid released from the subducted plate
  melts the magma above it, which rises forming
• an ISLAND ARC
• An ISLAND ARC is
• A chain of volcanic islands ? JAPAN

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CONVERGENCE between OCEANIC
OCEANIChttp//geomaps.wr.usgs.gov/parks/pltec/con
verge.html
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The OTHER boundary

• If plates are NOT CONVERGING and NOT DIVERGING,
  how else can they be moving?
• They can SLIDE PAST each other, this is called
• a TRANSFORM BOUNDARY
• An example of a transform boundary is
• the SAN ANDREAS FAULT

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PLATE BOUNDRY MOVEMENTSanimation

• http//www.classzone.com/books/earth_science/terc/
  content/visualizations/es0804/es0804page01.cfm?cha
  pter_novisualization

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CAUSES of PLATE MOTION

• The main 3 causes of plate motion
• MANTLE CONVECTION
• RIDGE PUSH
• SLAB PULL

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1) CONVECTION

• CONVECTION is
• the movement of heated materials due to
  differences in density that are caused by
  differences in temperature.

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1) CONVECTION

• During convection HOT material becomes (more
  or less) dense, so (rises or sinks).
• HOT ? LESS dense ? RISES
• During convection COLD material becomes (more
  or less) dense, so (rises or sinks).
• COLD ? MORE dense ? SINKS

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1) CONVECTION

• Plates at the surface move because of the intense
  heat in the Earths core that causes molten rock
  in the mantle layer to move.
• It moves in a pattern called a convection cell
  that forms when warm material rises, cools, and
  eventually sink down.
• As the cooled material sinks down, it is warmed
  and rises again.

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Isnt convection enough?

• Scientists once thought that Earths plates just
  surfed on top of the mantles giant convection
  cells, but now scientists believe that plates
  help themselves move instead of just surfing
  along.
• Just like convection cells, plates have warmer,
  thinner parts that are more likely to rise, and
  colder, denser parts that are more likely to
  sink.

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2) RIDGE PUSH

• 1st New parts of a plate rise because they are
  _______
• 
  WARM
• and the plate is thin.
• 2nd Hot magma rising to the surface forms new
  ______
• 
  CRUST
• 3rd The new crust pushes the plate out of its
  way.
• This process is called
• 
  RIDGE PUSH

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3) SLAB PULL

• When old parts of a plate sink down into the
  mantle at subduction zones because they are
  colder and thicker than the warm mantle material
  underneath them.
• As they sink, the heavy old parts of the plate
  pull the newer parts, still attached, with them.
• This is called
• SLAB PULL

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• A continental rift begins when molten lava rises
  up from deep in the Earth's interior and splits a
  continent open. As the fissure grows and widens,
  a future ocean floor spreads away from the ridge.
  Water should eventually flow into the cavity,
  making a new ocean.
• http//ase.tufts.edu/cosmos/view_picture.asp?id34
  7

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Divergent Boundaries

• Mid-oceanic ridges in oceanic mark divergent
  boundaries, as do volcanism earthquakes
• As oceanic lithosphere moved away from the ridge
  it cools it becomes denser and thicker it
  subsides.

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ACCRETIONanimation

• http//www.classzone.com/books/earth_science/terc/
  content/visualizations/es0808/es0808page01.cfm?cha
  pter_novisualization