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Plate Tectonics

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Plate Tectonics Transform Boundary San Andreas Fault (in California) Movement isn t the same along all parts of the fault. Some parts can move up to 5cm/yr, while ... – PowerPoint PPT presentation

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Title: Plate Tectonics


1
Plate Tectonics
2
Plate Tectonics
  • The Theory of Plate Tectonics is a theory that
    describes the formation, movements, and
    interactions of Earths lithospheric plates that
    move on the asthenosphere.

3
Theory of Plate Tectonics
  • The Theory of Plate Tectonics explains why
    earthquakes and volcanoes are likely to occur in
    particular locations and how new crust forms
    along the ocean floor.

4
Earthquakes and volcanic activity occur primarily
at the location of plate boundaries.
  • Plate boundaries are where 2 plates are pushing
    toward, pulling away, or sliding past each other.
    The strain and friction causes fractures in the
    earth, where earthquakes occur and where the
    fractures allow molten rock to flow to the
    surface.

5
Evidence for plate tectonics was also found in
igneous rocks which recorded the direction of
Earths magnetic field.
6
  • Mid-ocean ridge is a long chain of volcanic
    mountains on the ocean floor with a deep central
    valley. The mid-ocean ridge always shows the
    magnetic orientation of the North and South
    poles.

7
Mid-ocean Ridge
  • A pattern of bands on either side of the
    mid-ocean ridge show the changes in magnetic
    orientation.

8
Mid-ocean Ridges
  • Rocks at the center of the mid-ocean ridge are
    the youngest.
  • Mid-ocean ridges are boundaries where plates are
    moving apart.

(so the farther the rocks are from the mid-ocean
ridge the the rocks
are).
older
9
3 Main Hypothesis Which Cause of Plate Movement
  • Mantle Convection,
  • Ridge Push, and
  • Slab Pull

10
Mantle Convection
  1. Mantle Convection - the transfer (convection) of
    heat from Earths inner and outer cores moves the
    plates (like a convection belt)

11
Ridge Push
  • Ridge Push occurs at the Mid-ocean Ridges
  • - The hot molten magma rises up at the
    mid-ocean ridges and as it cools and hardens into
    a denser rock, the rock pushes out and slides
    down the ridge, allowing more new hot molten
    material to flow out of the mid-ocean ridge.

12
Slab Pull - Scientists believe this Slab Pull is
the greater factor out of the three theories.
  • Slab Pull occurs at a subduction boundary.
  • - The denser, heavier plate sinks underneath
    the other less dense plate. The edge of the
    subduction plate is much colder and heavier than
    the mantle, so it continues to sink and pull the
    rest of the plate along down with it.

13
CONTINENTAL DRIFT
  • Alfred Wegener proposed a hypothesis called
    Continental Drift which said the continents have
    drifted, or moved from one location to another
    over time.

14
Continental Drift was proven by
  • The shapes of the continents seem to match up
    (fit together like puzzle pieces)

15
Continental Drift was proven by
  • Certain fossils are on different continents
  • Example Mesosaurus reptile that lived about
    270 mya, fossils found only in parts of South
    America and Africa could have only happened
    when the 2 continents were once joined).

16
Continental Drift was proven by
  • Mountain chains found on 2 continents and would
    have matched up if the continents were joined.
  • Example Appalachian Mountains run along the
    eastern coast of US and through Great Britain.

17
Pangaea the giant supercontinent that existed
about 200 mya.
18
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19
TYPES OF PLATE BOUNDARIES
  • There are 3 main types of plate boundaries
  • Divergent Boundary,
  • Convergent Boundary, and
  • Transform Boundary

20
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21
Divergent Boundary
22
Divergent Boundary
  • Plates are moving apart
  • Occurs at Mid-ocean Ridges and at Rift Valleys
    (seafloor spreading)
  • Rift valley deep valleys at the center of a
    mid-ocean ridge.
  • Volcanic activity (underwater) and earthquakes
    take place along this boundary.
  • Hot springs also come up from hydrothermal vents
    on the ocean floor.

23
Divergent Boundary
  • Mid-Atlantic Ridge (Atlantic Ocean)

24
Divergent Boundary
  • East Pacific Rise (Pacific Ocean)
  • Transform faults run along the mid-ocean ridges

25
Convergent Boundary
  • Plates are moving toward each other.
  • 2 Types of Convergent Boundaries
  • Subduction
  • Collision

26
Convergent Boundary
  • Subduction occurs at
  • ocean to ocean plate moving toward each other
  • Ocean to continental plates moving toward each
    other
  • Oceanic crust is denser than continental crust,
    so oceanic crust will subduct underneath the
    continental plate
  • Deep sea trenches are formed
  • Volcanic island arcs are formed
  • Earthquakes occur

27
Convergent Boundary - Subduction
  • Islands of Indonesia (ocean to ocean)
  • Mariana Islands (ocean to ocean)
  • Mariana Trench (Pacific plate moving underneath
    the Philippine Plate)

28
Convergent Boundary - Subduction
  • Mariana Islands
  • Philippine and Pacific plates colliding (ocean to
    ocean)

29
Convergent Boundary
  • Collision Boundary occurs at
  • Continental to continental plate moving towards
    each other
  • Builds high mountain chains
  • Earthquakes occur along these boundaries

30
Convergent Boundary - Collision
31
Convergent Boundary - Collision
  • Our Appalachian Mountains were also formed this
    way long ago, but are not currently being formed.
    (rounded mountain tops been weathered and
    eroded down)

32
Convergent Boundary - Collision
  • Himalaya Mountains (sharp and jagged peaks)

33
Transform Boundary
  • 2 plates are sliding past each other.
  • Earthquake activity occurs here

34
Transform Boundary
  • San Andreas Fault (in California)
  • Movement isnt the same along all parts of the
    fault. Some parts can move up to 5cm/yr, while
    others havent moved in over a century.
  • North Anatolian Fault (in Turkey)
  • Fracture zones along mid-ocean ridges
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