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Plate Boundaries
Earth’s crust plus the upper mantle forms the
lithosphere.
Earth’s lithosphere is broken in a number of
different pieces.
How these pieces move and interact is what
plate tectonics is all about.
Convergent boundaries
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When 2 plates collide with one another.
Convergent boundaries
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When oceanic plates collide, one
subducts under the other.
This forms a valley in the ocean floor
called a trench.
An example of a trench is the Marianas Trench.
Convergent boundaries
When continental plates collide mountains form.
Convergent boundaries
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What happens if an oceanic plate and a
continental plate collide?
Which plate would subduct?
The oceanic plate must subduct under
the continental plate.
A continental plate is simply too buoyant
to subduct under an oceanic plate.
Divergent boundaries
A divergent boundary is the line between two
plates where they are moving apart.
Divergent boundaries
• Divergent boundaries can
be found on continents as
rift valleys.
• When a rift valley forms on
land, it may eventually split
the landmass.
Divergent boundaries
• Divergent boundaries can
also be found in the ocean
• Sea floor spreading occurs
at a mid ocean ridge.
Plate boundaries
• An edge of a
lithospheric plate
that slides by
another plate is
called a transform
fault boundary.
Transform fault boundaries
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When seen from
above, the feature will
appear to make a zigzag.
Causes Earthquakes
San Andreas Fault
Earth’s lithospheric plates
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Can you identify the three types of plate
boundaries labeled A, B, and C?.