Download Plate Tectonics

Plate Tectonics
Lynn Hahn
Tectonic Plate Theory
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Theory that explains the movement of
continents across the globe. It explains
why some earthquakes occur and
volcanoes on land and the ocean floor.
The Tectonic Plates
The Tectonic Plates
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Tectonic plates are
large pieces of the
lithosphere
2 different types of
plate: Oceanic and
Continental
How the plates move
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Convergent - Plates
are moving towards
each other
Divergent - Plates
are moving away
from each other
Transverse - Plates
are moving past
each other
Convergent Plate Boundaries
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Convergent –
when two objects
move towards one
another
The two objects
are two tectonic
plates

3 different types of
convergent boundaries
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Oceanic – Oceanic
Convergence (2 oceanic
plates converge
Oceanic – Continental
Convergence (1 oceanic
plate and 1 continental
plate)
Continental – Continental
Convergence (2 Continental
plates
Oceanic – Oceanic Boundaries
Oceanic – Oceanic Boundaries
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The slower moving
plate SUBDUCTS the
faster moving plate
Subducted plate – the
plate that is forced into
the mantle (the slower
plate)
Forms trenches and
volcanoes.
Hawaii is the result of
underwater mountain
ranges reaching above
water.
Oceanic – Continental
Boundaries
Oceanic – Continental
Boundaries
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Oceanic Plate is denser
Oceanic plate will
subduct the continental
plate
Forms offshore volcano
range and an
underwater trench
Ex. Andes Mountains
Continental – Continental
Boundaries
Continental – Continental
Boundaries
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Two continental plates
colliding
Neither plate subducts
the other
One plate will crumble
and break apart
Forms mountain ranges
and a higher plateau
Ex. Himalayan
Mountains and Tibetan
Plateau
Divergent Plate Boundary
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Divergent Plate Boundaries
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Moving apart and makes a
gap
Magma rises from
asthenosphere and creates
mountains as magma
cools
Ex. Mid Atlantic Ridge
Results in new crust
forming at a Rift Valley
Transform Plate Boundaries
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Transform Plate Boundaries
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
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
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Form Faults
Breaks in the
lithosphere
Rocks move past each
other
Ex. San Andreas Fault
Evidence for Plate Tectonics

In the middle of the oceans – The N and S are
magnetic Poles
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Magnets have a certain arrangement that makes them
magnetic. Every 200,000 years the earth’s magnetic
poles switch and S becomes North and North become
South
The magnetic rocks on earth reflect the direction of
magnetic North and magnetic South
Evidence Cont’d
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As magma comes out of the floor at a divergent
boundary, the material aligns itself the current magnetic
poles. After the magma cools, this become permanent.
Once the poles switch, the new magma will have a new
arrangement
PROOF!! – We see bands on the sea floor that
reflect changes in magnetic N and S. IF the sea
floor was not spreading, we wouldn’t
http://scign.jpl.nasa.gov/learn/plate4.htm
Other Evidence
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Fit of the Continents - Noted the similarity in
the coastlines of North and South America
and Europe and Africa. Today the fit is done
at the continental shelf and it is nearly a
perfect match.
Rock Similarities
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Rocks of same age match across ocean basins.
Termination of mountain chains.
http://geology.csupomona.edu/drjessey/class
/Gsc101/Plate.html
References and Pictures

US Geological Survey Western Earth
Surface Processes Team
and the National Park Service,
http://www2.nature.nps.gov/grd/usgsnps/plt
ec/pltec3.html#convergent.