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Don’t Break Your Plate
Notes on Plate Tectonics
Key Points
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Plate tectonics accounts for several features on the earth’s
surface
Seafloor spreading
 Subduction zones
 Earthquakes
 Volcanoes
 Mountain ranges
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Plates move due to mantle convection
How do plates move?
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The plates of the Earth float on top of the aesthenosphere
When mantle rock near the Earth’s core heats up it
becomes less dense and rises while the cooler rock near
the surface sinks—mantle convection
Moves plates a few centimeters each year
http://www.classzone.com/books/earth_science/terc/content/visual
izations/es0804/es0804page01.cfm?chapter_no=visualization
Three types of plate boundaries:
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Divergent
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Convergent
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Transform
Divergent Boundaries
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New crust is created as two plates pull away from each other
If two oceanic plates, the ocean will grow wider—seafloor
spreading
If two continental plates, creates a rift that will form two different
land masses
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Fills with water in the rift
Convergent
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Crust is destroyed and recycled back into the Earth’s
interior as one plate sinks below another plate—
subduction zones
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Mountains and volcanoes often form here
There are 3 types of convergent boundaries:
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Oceanic-continental convergence
Oceanic-oceanic convergence
Continental-continental convergence
Oceanic-Continental Convergence
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When an oceanic plate subducts below a continental plate:
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The continental plate rises to form mountains
When oceanic plate sinks deep, some pieces break off and get locked in
place—leads to earthquakes
Oceanic-Oceanic Convergence
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When one oceanic plate subducts under another:
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A deep ocean trench is formed
Creates undersea volcanoes that over time, can build up to form volcanic
islands
Continental-Continental Convergence
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When two continental plates meet head-on, neither one subducts.
Plates tend to buckle and rise up/sideways to form mountain
ranges
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i.e. Himalayan Mountains
Transform Boundaries
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Two plates are sliding horizontally past one another
Sometimes known as faults
Earthquakes take place along these boundaries