Download Theory of Plate Tectonics

Theory of Plate Tectonics
Plate Tectonics
Plate Boundaries
Causes of Plate Tectonics
Plate Tectonics
What is “Plate Tectonics”?
• The Earth’s crust and
uppermost solid mantle are
broken into sections called
plates
• Plates move around on top of
the mantle like rafts
How We Know.
March 8th, 2010 shortly after the Haiti, Chile,
Taiwan, and Turkey earthquakes.
September 26th, 2011
September 27th, 2012
September 19th, 2013
What is the Lithosphere?
• The crust and the uppermost
solid mantle = lithosphere
–100 km thick
–Less dense than the material
below it so it “floats”
What is the Asthenoshere?
• The plastic layer below the
lithosphere = asthenosphere
• The plates of the lithosphere
float on the asthenosphere
2 Types of Plates
• Oceanic plates - plates below the oceans
– Generally 1-5 km thick
– Basaltic (Mafic) rock
• Continental plates - plates that make up
the continents
– 10 – 100 km thick
– Granitic (Felsic) rock
– Less dense than Mafic rock, therefore
more buoyant than oceanic crust.
Divergent Boundaries
• Boundary between two plates
that are moving apart or rifting

• RIFTING causes SEAFLOOR
SPREADING
Features of Divergent
Boundaries
• Mid-ocean ridges
• rift valleys
• fissure volcanoes
Convergent Boundaries
• Boundaries between two
plates that are colliding
 
• There are 3 types…
Type 1
• OCEANIC to CONTINENTAL
• Ocean plate colliding with a
less dense continental plate
• Subduction Zone: where the
more dense plate slides under
the less dense plate
• VOLCANOES occur at
subduction zones
Andes Mountains,
South America
Type 2
• OCEANIC to OCEANIC
• Ocean plate colliding with
another ocean plate
• The more dense plate slides
under the less dense plate
creating a subduction zone
called a TRENCH
Aleutian Islands, Alaska
Type 3
• CONTINENTAL to CONTINENTAL
• A continental plate colliding
with another continental plate
• Have Collision Zones:
–a place where folded and thrust
faulted mountains form.
Transform Fault Boundaries
• Boundary between two plates
that are sliding past each other
San Andreas Fault, CA
California and Earthquakes
• Are earthquakes relatively frequent in
California?
• Will part of California eventually fall off into
the ocean?
• Why aren’t there many active volcanoes in
California compared to other plate
boundaries?
Los
Angeles
will
eventually
end up
where?
Any
subduction?
Any
divergence?
Rifting?
Possible in L.A.?
Causes of Plate
Tectonics
Convection Currents
• Hot magma in the Earth
moves toward the surface,
cools, then sinks again.
• Creates convection currents
beneath the plates that cause
the plates to move.
What Drives It: Convection
Questions...
• What are the three types of plate boundaries?
• In what relative direction do plates go for each?
• Which type of plate boundary causes a midocean ridge?
• What three features are present in and around a
mid-ocean ridge?
• Which boundary has a subduction zone…what
occurs at a subduction zone?
• What type of boundary is the San Andreas
Fault?
Questions...
• What causes plates to move?
• How is a convection current
formed?
Questions…
• What are the three types of convergent
plate boundaries?
• Name some geologic/geographic features
formed as a result of each.