Transcript Section 2 Chapter 6 Key Concept     Tectonic plates the size of continents and oceans move at rates of a few centimeters per year in response.

Section 2
Chapter 6
Key Concept
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Tectonic plates the size of
continents and oceans move at
rates of a few centimeters per
year in response to movements in
the mantle.
Where would all of the energy
for force to move a continent
come from?
Scientists formed a theory to
explain how continents move.
Plate Tectonics is the theory that
Earth’s lithosphere is divided into
tectonic plates that move around
on top of the asthenosphere.
Tectonic Plates
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Pieces of the lithosphere
that move around on top
of the asthenosphere are
called tectonic plates.
Some tectonic plates
contain both continental
and oceanic crust.
A Tectonic Plate Close-Up
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Earth’s lithosphere (crust) is
like a giant jigsaw puzzle.
Tectonic plates are made up
of oceanic crust and
continental crust as well as
part of the mantle.
The thickest part of the
continental crust is under
mountains
The thinnest part of the
crust is under the ocean.
Like Ice Cubes in a Punch Bowl
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Tectonic plates “float” on the asthenosphere in a
similar way to ice in water or a punch bowl.
Ice cubes cover the surface and bump into each other.
Part of the cubes are below the surface and displace the
water.
The larger cubes (plates) displaces more water than the
smaller cubes (plates)==continental lithosphere
displaces more asthenosphere than oceanic lithosphere.
Tectonic Plate Boundaries
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A boundary is a place
where tectonic plates
meet.
Boundaries are
located by studying
the locations of
earthquakes,
volcanoes, and
landforms such as
mid-ocean ridges and
ocean trenches.
Three Types of Plate Boundaries
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Divergent
Convergent
Transform
Convergent Boundaries
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Two continental plates collide
(crash into each other) may for a
high mountain range which
develops over millions of years.
An oceanic plate may collide with
a continental plate. The oceanic
plate will slide under the
continental plate (process called
subduction). Subduction may
cause a chain of volcanoes to
form.
Two plates of oceanic crust
collide, the denser (heavier) of
the 2 will subduct causing an
island arc (volcanic
islands==Hawaii)
Divergent Boundaries
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The boundary at which 2
tectonic plates separate is a
divergent boundary.
Some divergent boundaries
appear on land, but most are on
the sea floor, causing mid-ocean
ridges.
As plates pull away from each
other, fractures (breaks) form in
the lithosphere (crust).
Magma rises through these
fractures to the ocean floor and
forms new lithosphere (crust).
Transform Boundaries
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The boundary at which two
tectonic plates slide past one
another horizontally is a
transform boundary.
Most transform boundaries
occur in the sea floor at midocean ridges. These give midocean ridges the zigzag patterns
that are seen on maps of the sea
floor.
The San Andreas fault in
California is a transform
boundary. The fault is where the
Pacific and North American
plates slide past each other.
Teachers: make sure you are hooked
up to the internet 
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http://www.seed.slb.com/en/scictr/watch/living_planet/plate_boundaries/plate_move.htm
Causes of Tectonic Plate Motion
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Tectonic plate motion is Slab pull=sinking lithosphere
caused by density
differences that are caused
by the flow of heat within
the earth.
Earth’s core and mantle are
very hot because they
contain minerals that have
radioactive atoms. These
atoms release heat as they
decay. Heat always flows
from a warmer area to a
colder area. Thus, heat
from Earth’s center flows
toward the surface.
Convection.
Ridge push=makes
Lithosphere go downhill
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When rock is heated, it expands, becomes less
dense, and rises toward the surface of the earth.
At the surface, cold, dense rock of the
lithosphere tend to sink during subduction.
This process causes convection currents in the
mantle.
Tracking Tectonic Plate Motion
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Tectonic plate movement
is measured in
centimeters per year.
The average rate of
movement for different
plates ranges between 2.5
and 15 centimeters per
year.
Scientists use GPS to
record exact distances
plates move.
Scientists use sea-floor
spreading to measure the
rate of movement of
oceanic plates.
Summary
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Plate tectonics is the theory that explains how pieces of
Earth’s lithosphere move and change shape.
Tectonic plates are large pieces of the lithosphere that
move around on top of the asthenosphere.
Boundaries between tectonic plates are classified as
convergent, divergent, or transform.
Convection is the main driving force of plate tectonics.
Tectonic plates move a few centimeters per year.
Scientists measure this rate by using GPS or by using
sea-floor spreading.
Ready for a Quiz?
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http://science.whoi.edu/quiz/tecto-quiz/quizmaker.html