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Plate Tectonics
22.4
Plate Tectonics
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Theory that explains the formation
and movement of Earth’s plates
Continental Drift
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Theory put forth by Alfred Wegener
that hypothesized that continents
looked liked they fit together like
pieces of a puzzle
One large supercontinent was formed
called Pangaea “all land”
Pangaea’s eventual split is called
continental drift, powered by sea
floor spreading
Mid Ocean Ridge
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In the 1950’s, sonar was used to
map the sea floor
Mountains were discovered
The mid ocean ridge is the Earth’s
longest mountain chain
Alongside it, runs a deep valley
Mid Ocean Ridge
Formation of Oceanic Crust
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In the crack along the mid ocean
ridge, magma rises to the surface
As it cools, it gets pushed aside by
new magma
Older crust gets pushed farther and
farther apart and the sea floor
spreads
Sea Floor Spreading
Subduction
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When oceanic plates collide with
continental plates, the oceanic plate
sinks below it because it is denser
Oceanic plate is destroyed
Subduction
Theory of Plate Tectonics
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Movement of the plates based on the
convection of the mantle
Heat from the core and radioactive
decay are two engines that drive
plate movement
Plate Boundaries
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Divergent: plates are pulling apart
Convergent: plates are pushing
together
Transform: plates are sliding side by
side
Divergent
Convergent
Transform
Mountain Building
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Mountains form along plate
boundaries
Convergent: Himalayas, Andes,
Swiss Alps
Divergent: Iceland
Essential Questions
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What is the theory of plate tectonics?
What evidence supports plate
tectonics?
How is rock in the ocean formed?
What force powers the movement of
the continents?
Describe the three ways in which the
plates move along plate boundaries.
References
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http://www.platetectonics.com/book/images/Midoceanridge.jpg
http://library.thinkquest.org/17457/platetectonics/seafloor.jpg
http://www.whoi.edu/annualreport02/images/scihigh_subduction_
en.gif
http://www.oceansjsu.com/images/exp5_divergent.GIF
http://www.bgs.ac.uk/discoveringGeology/hazards/earthquakes/i
mages/convergentBoundary.jpg
http://www.cms.fu-berlin.de/geo/fb/elearning/geolearning/en/mountain_building/plate_tectonics/media
/transform1.jpg