PLATE
TECTONICS
Nafisa
Skeie
What is plate tectonics?
The build up of plates…?
Or is it the build up of food onto a plate…?
Geographically…
Plate: Large, rigid slab of Earth’s solid rock
+ Tectonics: From the Greek root “to build”
Plate Tectonics =
The term which refers
to how the Earth’s
surface is built of
plates
Earth’s
Layers
http://homepage.usask.ca/~src594/thestructureofearth.jpg
EGGS-celent!
http://earthquake.usgs.gov/learning/teachers/EarthEgg.pdf
Crust
Mantle
Outer Core
Inner Core
The Plates
-Plates: large, rigid slab of Earth’s solid rock
- are broken pieces from the lithosphere layer which is the crust of the Earth
- ride on the hotter and weaker layer of the upper portion of the mantle called the
asthenosphere
- due to the various pressure in the upper mantle, the layer is plastic which allows the
plates of the lithosphere to move around
--> Theory of Plate Tectonics: Movements of the Earth’s plates
http://stloe.most.go.th/html/lo_index/LOcanada1/102/images/L02_3.jpg
Earth’s Major Plates
http://www.enchantedlearning.com/egifs/Earthsplates.GIF
Plate Boundaries
Transform Fault (Sliding)
-two plates grind past each other without
the production or destruction of lithosphere
-San Andreas Fault in California.
-> Pacific plate is moving toward the
northwest grinding past the North American
plate which is traveling in the opposite
direction.
- Earthquakes are triggered along the fault
boundaries.
http://stloe.most.go.th/html/lo_index/LOcanada4/403/images/4_1.jpg
http://www.biog11051106.org/demos/106/unit08/media/san-andreas-fault.jpg
\
Plate Boundaries
Divergent (Constructive)
Oceanic plate & Oceanic plate
http://stloe.most.go.th/html/lo_index/LOcanada4/403/images/1_1.jpg
-Plates move away from each other.
-When two plates diverge, factures occur
which are immediately filled with molten rock
that wells up from the asthenosphere. This
hot material cools and creates a new seafloor.
-As a result, new oceanic crust (lithosphere)
is continuously being created between the
diverging plates.
-The older crust moves away from the
boundary, as it does so, it cools and contracts
hence increasing in density and in thickness.
-This is why the older and cooler oceanic
crusts are deeper.
Hyrdrothermal
vents
Divergent
Plate Boundaries
Continental plate & Continental plate
http://stloe.most.go.th/html/lo_index/LOcanada4/403/images/1_2.jpg
-Two continental plates
moves apart from each
other
-The East African rift
valleys represent the
initial stage in the
breakup of a continent.
-Volcanic mountains such
as Kilimanjaro and
Mount Kenya are
examples of the rift
valleys that were formed
by the associated faulting
http://taos-telecommunity.org/EPOW/EPOWtaking place.
Archive/archive_2008/EPOW081027_files/P1180531%20Rift%20Valley%20escarpmen
ts%20L&R_big.jpg
Plate Boundaries
Convergent (Subduction)
-Plates move towards each other,
resulting in subduction (consumption)
of oceanic lithosphere into the mantle.
-When two plates converge, the
leading edge of one is bent
downward, allowing it to descend
beneath the other.
-This region is called a subduction
zone.
-There are three types of convergent
boundaries.
http://stloe.most.go.th/html/lo_index/LOcanada4/403/images/3_1.jpg
Plate Boundaries
Convergent
Oceanic plate & Continental plate
http://www.sema.go.th/files/Content/science/k4/0035/F01/images/Th/03/3_2.jpg
-When a continental plate collides with an
oceanic plate, the less dense continental plate
will continue on its course while the denser
oceanic plate will sink under the continental plate
and into the asthenosphere.
-As the descending plate increases in depth, the
heat generated causes partial melting of the
mantle creating magma which will accumulate
beneath the overlying continental crust.
-This can result in explosive volcanoes
-Example is the Andes in South America
Ushuaia Bay with the
southernmost tip of
Andes in the
background in
Argentina
http://img2.travelblog.org/Photos/841/2784/f/9037-Ushuaia-bay-with-the-southernmost-tail-of-the-Andesin-the-background-0.jpg
Plate Boundaries
Convergent
Oceanic plate & Oceanic plate
http://stloe.most.go.th/html/lo_index/LOcanada4/403/images/3_3.jpg
-Two oceanic plate convergence, one will
descend beneath the other.
-Triggers volcanic activity …just like the
oceanic-continental convergence, but the
volcanoes forms on the ocean floor.
-If the activity continues the volcanoes will
emerge as islands in the ocean
- Examples are the Mariana Islands in the
western Pacific Ocean and the Tonga
Metis Volcano
is one of the
Tonga Islands
http://www.cartage.org.lb/en/themes/sciences/earthscience/geology/volcanoes/currentvolcanoes/
metis2.gif
Plate Boundaries
Convergent
Continental plate & continental plate
-When two plates carrying continental
crust converge it causes collision.
-Since both plates are of low density and
buoyant by the nature of the continental
rock, neither will subduct.
-Folding and deforming of sediments
along the continental margins are then
formed.
-Example is the Himalayas which are a
result of the Australian-Indian plate
ramming into the Eurasian plate.
http://help.berberber.com/me
mbers/sajalarora/albums/natu
ral-beauty-india/2026himalayas.jpg
http://stloe.most.go.th/html/lo_index/LOcanada4/403/images/3_4.jpg
Activity time!
Snack tectonics
Now you can EAT your snacks!
Questions?
Resources
• http://stloe.most.go.th/html/lo_index/LOcan
ada4/403/html/1_en.htm
• http://en.wikipedia.org/wiki/Tectonic_plate
#Divergent_.28constructive.29_boundarie
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