2. Plate Tectonics
• Pieces of the lithosphere that move around
• Each plate has a name
• Fit together like jigsaw puzzles
• Float on top of mantle similar to ice cubes
in a bowl of water
3. Continental Drift
•Alfred Wegener 1900’s
Continents were once a single
land mass that drifted apart.
•Fossils of the same plants
and animals are found on
different continents
•Called this supercontinent
Pangea, Greek for “all Earth”
7. Sea Floor Spreading
• Mid Ocean Ridges – underwater mountain
chains that run through the Earth’s Basins
• Magma rises to the surface and solidifies
and new crust forms
• Older Crust is pushed
farther away from the ridge
Two Volunteers to
Demonstrate
12. Divergent Boundaries
• Places where plates are coming apart
• Forms a central valley called a rift
• Earthquakes occur along the faults
• Volcanoes form where the magma reaches the
surface.
• Plate separation is a slow process. For
example, divergence along the Mid Atlantic ridge
causes the Atlantic Ocean to widen at only about 2
centimeters per year.
Animation
16. Convergent Boundary
•Places where plates crash or
crunch together
•Collisions are very slow and
last millions of years
•Mountains, earthquakes, and
volcanoes form where plates
collide
•Rockies in North
America, the Alps in
Europe, the Pontic Mountains
in Turkey, the Zagros
Mountains in Iran, and the
Himalayas in central Asia
were formed by plate
18. Transform Boundaries
•Places where plates slide past each other
•Marked in some places by linear valleys
where rock has been ground up by the sliding
20. Subduction Zone
• When two oceanic plates collide, the younger of the two plates,
because it is less dense, will ride over the edge of the older plate.
21. Review
• Name the 3 main layers of the Earth.
• What is a tectonic plate?
• What was Pangea?
• What is Sea-Floor spreading?
• Name the three different types of plate
boundaries and one location on Earth for each
one
22. 1. In your basket
you should
have wax
paper, a plastic
spoon, fruit
roll-up and a
graham
cracker
2. I will come
around and
put a small
amount of
icing on your
wax paper.
23. 1. Divergent
Boundary
– Notice how the
frosting is
exposed and
pushed up where
the plates are
separated?
– This is how
magma comes to
the surface where
plates are moving
apart at divergent
boundaries
– When plates
begin to pull apart
24. 1. Continent-Oceanic
Convergent
Boundary
– The graham
cracker
represents the
continental
crust, which is
thicker and less
dense than
oceanic crust
(fruit roll-up).
– After you
complete Step
3, the oceanic
plate will be
subducted
below the
continental one.
25. 1. Continent – Continent
Convergent Boundary
– This is when two
continents collide
– Notice how the wet
edges crumble?
– This is how mountains
are made at
convergegnt plate
boundaries.
– When continents
move toward each
other, there is
nowhere for the rock
to go but up.