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Transcript 
8th Grade Science
© Fall 2005, Pflugerville ISD, 8th Grade
Chapter 17- Plate Tectonics
Section 1: Restless Continents
Section 2: The Theory of Plate
Tectonics
Section 3: Deforming the Earth’s
Crust
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
What Do You Think?
Explain why the following statement is
true or false:
The state of Texas is moving to the west
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•As the ocean
floor spreads,
Europe moves
east and North
America
moves west
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•The earth is
layered like a
chocolatecovered cherry
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•The layers
have different
properties and
different
compositions
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•The
lithosphere is
the cool,
outermost layer
of the Earth
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•It is divided into
huge pieces
called tectonic
plates, which
move on the
asthenosphere
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•Asthenosphere
is the solid, soft
layer of the
mantle below the
lithosphere
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•Asthenosphere
is made of
mantle rock that
flows slowly,
allowing
tectonic plates
to move on it
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•The mesosphere
is the solid lower
part of the mantle
below the
asthenosphere
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•The outer core
is the outer shell
of Earth’s core.
It is made of
liquid iron and
nickel
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•The inner core
is a sphere of
solid iron and
nickel
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
© Fall 2005, Pflugerville ISD, 8th Grade
•The core is the
solid cherry
surrounded by
gooey mantle
covered with a
thin chocolate
crust
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
Alfred Wegener
1880-1930
© Fall 2005, Pflugerville ISD, 8th Grade
•Alfred Wegener,
a German scientist,
first had the idea
that continents can
drift around the
globe
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•Wegener’s theory
of continental
drift explained
why some land
masses fit like
puzzle pieces
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•Continental drift also explained
why similar fossils are found
separated by the oceans
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•Wegener’s theory
had the continents
plowing through
the oceans like
this ship plows
through ice
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•As is usual with
new theories,
most scientists
didn’t believe in
continental drift
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
Glomar Challenger
© Fall 2005, Pflugerville ISD, 8th Grade
•In the late
1960s, this ship
was designed to
drill into the
ocean floor for
core samples
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•The core samples
revealed that rock
at the center of the
Atlantic (Red) was
younger than rock
at the edges (Blue)
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•The process by which new oceanic
crust forms at mid-ocean ridges was
called seafloor spreading
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•Scientists later discovered that the
earth’s magnetic field changes
polarity every few thousand years
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•As the rock cools, it records these
magnetic reversals in the seafloor
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•With continental fit,
seafloor spreading,
and magnetic
reversals as proof,
Wegener’s theory
Alfred Wegener was proved!
1880-1930
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Do the Continents Move?
•With this new theory of Plate
Tectonics, Wegener’s idea of a
supercontinent was accepted
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
The Theory of Plate Tectonics
What Do You Think?
Consider the amount of energy it would
take for humans to pick up a public school
and move it a mile. What forces do you
think cause the movement of the
continents?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
The Theory of Plate Tectonics
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
The Theory of Plate Tectonics
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
The Theory of Plate Tectonics
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
The Theory of Plate Tectonics
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
Tectonic Plate Boundaries
•Where the
plates meet,
three types of
plate
boundaries
can form…
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
Tectonic Plate Boundaries
Convergent Boundary
© Fall 2005, Pflugerville ISD, 8th Grade
•A convergent
boundary is
where two
tectonic plates
collide, or run
into each other
Unit 4 : Chapter 17 : Section 2
Convergent Boundaries
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
Convergent Boundaries
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
Convergent Boundaries
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
Tectonic Plate Boundaries
Divergent Boundary
© Fall 2005, Pflugerville ISD, 8th Grade
•A divergent
boundary is
where two
tectonic plates
separate from
each other
Unit 4 : Chapter 17 : Section 2
Divergent Boundary
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
Tectonic Plate Boundaries
Transform Boundary
© Fall 2005, Pflugerville ISD, 8th Grade
•A transform
boundary is
where two
tectonic plates
slide past one
another
horizontally
Unit 4 : Chapter 17 : Section 2
Transform Boundary
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
Tectonic Settings
Scientists use plate tectonics to explain how
landforms like mountains and ocean basins form
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
Tectonic Settings
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
Tectonic Settings
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
Tectonic Settings
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
Tectonic Settings
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
Deforming the Crust
What Do You Think?
The Indian Ocean tsunami of 2004
originated at a subduction zone. How did
plate tectonics cause these waves that
killed over 100,000 people?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Deforming the Crust
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Deforming the Crust
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Deforming the Crust
•Stress is
the amount
of force per
unit area that
is put on a
rock
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Deforming the Crust
•Strain is
any change
in a rock’s
shape
caused by
stress
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Deforming the Crust
•The deformed
strata have
been strained
by the stress
of compression
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Deforming the Crust
•Folding is a type of strain that
occurs when rocks bend
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Deforming the Crust
•Faulting is a type of strain that
occurs when rock breaks
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Building Mountains
Mt. Everest, Himalayas
© Fall 2005, Pflugerville ISD, 8th Grade
•Almost all
mountains
are formed at
tectonic plate
boundaries
Unit 4 : Chapter 17 : Section 3
Building Mountains- Divergent
•The midocean ridge
system is
made of two
types of
mountains:
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Building Mountains- Divergent
•Fault-block
mountains
form where
the crust is
rifting, or
separating
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Building Mountains- Divergent
•Volcanic
mountains
form outside
of the Rift
Zone, on
either side
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Building Mountains- Convergent
Convergent Boundary
© Fall 2005, Pflugerville ISD, 8th Grade
•At convergent
boundaries,
either volcanic
or folded
mountains can
form
Unit 4 : Chapter 17 : Section 2
Building Mountains- Convergent
© Fall 2005, Pflugerville ISD, 8th Grade
•In Alaska, the
subduction of
the oceanic
Pacific plate
has created a
chain of
volcanoes
Unit 4 : Chapter 17 : Section 3
Building Mountains- Convergent
•When ocean was between India
and Asia, there were volcanoes
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Building Mountains- Convergent
•As the continents collide, they
create only folded mountains
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Building Mountains- Convergent
•The Nazca
Plate is
being
subducted
beneath the
SA Plate
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Building Mountains- Convergent
•The result is a
trench in the
ocean and a
chain of
volcanoes on
the continent
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Let’s Review!
-1-
Describe Alfred
Wegener’s theory of
continental drift.
How is this different
from the modern theory
of plate tectonics?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
Let’s Review!
-2-
What are the three
possible driving forces
of plate tectonics?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 2
Let’s Review!
-3-
What kind of mountains
would you expect to find
near an ocean trench?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
Let’s Review!
-4-
What kinds of mountains
would you expect to find
at a mid-ocean ridge?
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 3
http://www.scotese.com/
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17
Pre-AP Extensions
© Fall 2005, Pflugerville ISD, 8th Grade
Unit 4 : Chapter 17 : Section 1
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