Download Plate Boundaries

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Plate Boundaries
 Imagine a single plate, moving in one direction on Earth’s
surface.
 One edge of the plate—the divergent boundary—moves
away from things.
 The opposite edge—called the leading edge or convergent
boundary bumps into anything in the way.
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Plate Boundaries
 An edge of a lithospheric plate that slides by another plate
is called a transform fault boundary.
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Plate Boundaries
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Plate Boundaries
 Divergent boundaries are found in the ocean as midocean ridges.
 A divergent boundary is the line between two plates where
they are moving apart.
 This type of boundary is found over the rising plume of a
mantle convection cell.
 Divergent boundaries can also be found on continents as
rift valleys.
 When a rift valley forms on land, it may eventually split
the landmass.
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Divergent Boundaries
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Convergent Boundaries
 When oceanic plates collide, one subducts under the other.
 This forms a valley in the ocean floor called a trench.
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Convergent Boundaries
 There are three styles of convergent plate boundaries
 Continent-continent collision
 Continent-oceanic crust collision
 Ocean-ocean collision
Ocean-ocean
collision
Continent-oceanic
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Continent-continent
Convergent Boundaries
Ocean-ocean collision
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Convergent Boundaries
 The oceanic plate must subduct under the continental
plate.
 A continental plate is simply too buoyant to subduct
under an oceanic plate.
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Collision of Nazca
and south American
Plates
Continentoceanic crust
collision
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Mountains And Convergent
Boundaries
 The continents cannot be sucked into the trench because
their granite rocks.
 The two continents collide!
 Mountain ranges are formed when continents collide.
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Formation of Himalayas
 India used to be an island, but about 15
million years ago it crashed into Asia
(see map).
 As continental crust was pushing against
continental crust the Himalayan
mountain belt was pushed up.
 “Mountains” were also pushed down
into the mantle as the normally 35 km
thick crust is approximately 70 km thick
in this region.
 Mt Everest is the highest altitude
mountain on our planet standing
8,840 meters high. This means that
below the surface at the foot of the
mountain the crust is a further 61 km
deep!!
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Transform Boundaries
 Where plates slide past each other
 The third type of boundary are transform boundaries,
along which plates slide past each other.
 The San Andreas fault, adjacent to which the US city of
San Francisco is built is an example of a transform
boundary between the Pacific plate and the North
American plate.
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Transform Fault Boundaries
 A good clue for locating transform faults is offsetting.
 When seen from above, the feature will appear to make a
zig – zag .
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Slickenslides, evidence of plate
boundaries
 The effect of rock moving
against rock is evidence of
plate boundaries.
 The rock surface moving to
the right is called slickensides
because it is smooth and
polished.
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What are Hotspot Volcanoes?
 Hot mantle plumes breaching the surface in the
middle of a tectonic plate
The Hawaiian island chain are
examples of hotspot volcanoes.
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Where do earthquakes form?
Figure showing the tectonic setting of earthquakes
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