Transcript Slide 1

Earth is composed
of 3 layers:
1. Core
2. Mantle
3. Crust
1. Core (inner &
outer) – made of
iron & nickel
a. inner – super
hot solid
-about 4,000 mi.
below surface of
earth
b. outer – super
hot liquid
-about 1,800 mi. below the
surface of earth
-temperatures can reach
8,000*F
2. Mantle
-hot, dense
mostly liquid
rock
-pockets of
magma (rise &
fall)
-made of
silicon,
aluminum,
iron,
magnesium,
and oxygen
3. Crust
-rocky shell
which forms
earth’s surface
-broken into
more than a
dozen slabs of
rock called plates
that rest on layer
of the upper
mantle
-these plates
carry earth’s
oceans &
continents
-Continental Drift :
theory that
continents were
once joined and
then slowly drifted
apart
*super-continent
was called Pangaea
PANGAEA
-Plate Tectonics – term scientists use to
describe the activities of continental drift and
magma flow which create many of Earth’s
physical features
*plates crash into each other, pull apart, or grind
and slide past each other (about 4 inches or
less per year)
-Why do plates move?
-convection currents
*hotter material is less
dense & rises (toward
crust of Earth)
*cooler material is more
dense & sinks (toward
core of Earth)
*creates continuous
circular
motion/movement
Why might a scientist want to study plate
tectonics?
Divergent Boundary
-Plates move apart (rift) from each other (tension)
1. Continental-Continental = creates gap (rift
valley) in which water can flow in
*ex: Red Sea; Great Rift Valley
2. Oceanic-Oceanic = magma rises up & creates
new crust on edges of the 2 plates
-enlarges the ocean floor & forms underwater
mountain ranges called ocean ridges
*example: Mid-Atlantic Ridge
– North American plate & Eurasian
& African plates pulling apart
Convergent Boundary
In general:
- Plates move
toward each
other & collide
(compression)
- One plate is
forced below
the other
(subduction)
1. Oceanic-Continental
-subduction occurs = heavier sea plate
dives beneath lighter continental plate
*sea plate begins to melt into magma 
pressure builds  magma bursts thru crust to
form volcanic mtns
*ex: Andes
Mountains
in S.
America –
collision of
Nazca and
SA plates
2. OceanicOceanic
-subduction
occurs
*sea plate
begins to melt &
magma rises to
ocean surface in
form of volcanic
islands
*example:
Philippine islandscollision of
Philippine &
Pacific
plates
3. ContinentalContinental
-pressure builds
until one plate is
subducted
*sometimes sinking
plate melts & rises as
volcanic mountains are
formed
*example: Himalaya
mountains (South
Asia) – collision of
Indian & Eurasian
plate
Transform Boundary
-Plates slide past each other along faults
(cracks in the earth’s crust)
- Crust is pulled and stretched (tension) until
tension is released (Earthquake)
-example: San Andreas Fault in California
HOT SPOTS
-Magma rises thru
the tectonic plate
-The magma erupts
on the surface as
lava & hardens to
form volcanic islands
-Magma continues to
rise from the hot
spot, building up an
undersea volcano
that will one day
become an island
-a chain is formed
Animations
Hot Spot Animation
Guess the
Tectonic Activity!
Oceanic-Oceanic Convergent
Oceanic-Oceanic Divergent
Transform
Continental-Continental Convergent
Continental-Continental Divergent
Oceanic-Continental Convergent