Plate Tectonics 2015
The Earth is divided into 4 layers.
CRUST
MANTLE
INNER
CORE
OUTER
CORE
The Crust
• Layer of rock that forms Earths outer skin
• Solid rock included both dry land and ocean floor
(rocks, mountains, soils, water)
• Thin layer (similar to paper thin layer of an onion)
• Ranges from 5-40 km thick (70km underneath
mountains)
• Composition: oxygen, silicon, aluminum, calcium, iron,
sodium, potassium, magnesium
• Basalt = oceanic crust
• Granite = continental crust
• Temperature: whatever is on the surface
Crust
• The plates move along smoothly but
sometimes they get stuck and pressure
builds up.
Mantle
• Rock that is very hot and
bendable but solid at the
same time.
• Solid upper mantle and
crust = lithosphere
(100km thick)
• Under lithosphere =
asthenosphere
• So hot that it behaves like
a plastic material; it flows
• 2,900 km thick
• Temperature 870°C
• Composition: silicon,
oxygen, iron, magnesium
Mantle
•The movement of
the mantle create
the movement of
the Earth’s plates.
Outer Core
• Composition: iron and nickel
• Temperature: 2200°C
• State of Matter: thick liquid (molten metal)
• LOTS of pressure
• 2,250 km thick
Inner Core
• Composition: iron and nickel
• Temperature: 5000°C
• State of Matter: Dense solid metal
• Extreme pressure (squeezes that atoms
of iron and nickel so much they can’t
spread out and become liquid)
• 1,200 km thick
Earth’s Magnetic Field
• Currents in the liquid outer core force the solid inner
core to spin. The inner core spins at a slightly faster
rate than the earth’s rotation. Because of this
movement, it causes Earth to act like a giant bar
magnetic. The magnetic field protects us from the
sun’s damaging UV rays.
Earth’s Magnetic Field
• Earth is a gigantic magnet
surrounded by a magnetic
field
• Dipole (bar magnet)
• Source is the liquid outer core
• Molten iron in the liquid outer
core flows around the solid
inner core
• Unlike bar magnet the Earth’s
field changes over time
Convection Currents
• As liquid heats up, it becomes less dense and rises.
When it is away from the heat source, it cools down
and becomes more dense and sinks. Heat from the
lower mantle and the cores (inner and outer) cause
convection currents in the asthenosphere.
Moves up
Cools Down
Heats Up
Moves down
Heat source
Plate tectonics
– theory that states that pieces of the lithosphere are
in constant slow motion driven by convection
currents in the mantle
Convergent Boundaries
• Two plates collide
• The denser plate sinks below the
more buoyant plate in a process
called subduction.
Examples
• Ocean-Continent: Subduction and
Volcanic arc
• Cascade Mountains (Mt. St. Helens, Mt.
Rainier), Andes Mountains
• Continent-Continent: Mountains Form
• Himalayan Mts.
• Ocean-Ocean: Subduction and Volcanic
Arc
• Lesser Antilles
Divergent Boundaries
• Two plates separating
Examples
• Ocean-Ocean: Seafloor spreading
• Mid-Atlantic Ridge
• Continent-Continent: Widening and
separating of land
• Eurasian Plate, African Rift Valley
Transform Boundaries
• Two plates slide horizontally past one another
Examples
• Continent-Continent: Earthquakes
• San Andres Fault
• Ocean-Ocean: Earthquakes
• East Pacific Rise
Plate Boundaries Foldable
Plate Motion Data Table
1
Plate Name
2
Latitude
within
Plate
3
Longitude
within Plate
Example
20°S
120°E
Pacific
20 N
160 W
North American
60 N
60 W
Caribbean
15 N
80 W
Eurasian
40 N
0
Nubia/African
0
0
Cocos
10 N
110 W
South American
0
60 W
Page 35
4
5
6
7
Revised
Latitude
(degrees N
(+), S (-))
Revised
Longitude
(degrees E(+),
W(-))
Direction
(clockwise
from N)
Speed
(mm/yr)
-20
+120
Plate Motion Data Table
1
Plate Name
2
Latitude
within
Plate
3
Longitude
within Plate
Page 35
4
5
6
7
Revised
Latitude
(degrees N
(+), S (-))
Revised
Longitude
(degrees E(+),
W(-))
Direction
(clockwise
from N)
Speed
(mm/yr)
Example
20°S
120°E
-20
+120
Pacific
20 N
160 W
+20
-160
North American
60 N
60 W
+60
-60
Caribbean
15 N
80 W
+15
-80
Eurasian
40 N
0
+40
0
Nubia/African
0
0
0
0
Cocos
10 N
110 W
+10
-110
South American
0
60 W
0
-60
Plate Motion Data Table
1
Plate Name
2
Latitude
within
Plate
3
Longitude
within Plate
Page 35
4
5
6
7
Revised
Latitude
(degrees N
(+), S (-))
Revised
Longitude
(degrees E(+),
W(-))
Direction
(clockwise
from N)
Speed
(mm/yr)
Example
20°S
120°E
-20
+120
Pacific
20 N
160 W
+20
-160
-59.73
105.11
North American
60 N
60 W
+60
-60
245.22
25.67
Caribbean
15 N
80 W
+15
-80
252.93
29.68
Eurasian
40 N
0
+40
0
239.35
20.12
Nubia/African
0
0
0
0
249.12
16
Cocos
10 N
110 W
+10
-110
25.5
16.95
South American
0
60 W
0
-60
257.34
46.76
1.
Which plates do you think will impact North America? Shade it in with your
pencil
• Add the names of those plates to column 1
2.
Choose a location with in each plate where it is easy to read the latitude and
longitude.
• Put a dot on the location
• Add the latitude and longitude of each location within the plate to the
columns 2 and 3
3.
Convert the latitude and longitude of the locations and enter them into
columns 4 and 5
• Revised Latitude:
If location is °N the number is positive. (20°N = +20) If
location is °S the number is negative. (20°S = -20)
• Revised Longitude: If location is °E the number is positive. (20°E = +20) If
location is °W the number is negative. (20°W = -20)
4.
Then go to the plate motion calculator site (http://tectonics.rice.edu/hs3.html
5.
Enter the name of the plate and your revised latitude and revised longitude
(column 4,5) for the location within that plate. Click on Execute calculation.
6.
Enter Speed (Rate) and Direction (Azimuth) into the table. Note: “cw” stands for
clockwise.
Seafloor Spreading Notes
Page 36
Read pages 194-200 in the textbook. Then answer the following questions
and define the words below
1.
What is seafloor spreading?
2.
What evidence is used to
support seafloor spreading?
• mid-ocean ridge
• seafloor spreading
• magnetic reversal
• normal polarity
• reversed polarity
Seafloor Spreading Notes
Read pages 194-200 in the textbook. Then answer the
following questions
1. What is seafloor spreading?
2. What evidence is used to support seafloor spreading?
• mid-ocean ridge
• seafloor spreading
• magnetic reversal
• normal polarity
• reversed polarity
- mountain range located on
the seafloor in the middle of
the ocean
- new oceanic crust forms at a
mid-ocean ridge as - old oceanic
crust moves away from the ridge
- event in which the magnetic
field reverses direction
- today’s magnetic field;
magnets orient themselves to
point north
- magnetic field in - which
magnets orient themselves to
Process of Seafloor Spreading
1. At the mid ocean ridge molten material comes up
from the mantle, cools, hardens and becomes
new crust
2. The new crust spreads out and pushes the old
rock to the sides in a continuous process
3. When older oceanic crust reaches a continental
crust the more dense oceanic plate is subducted
down and forms a trench on the surface.
4. The older crust melts back into the mantle and is
recycled by convection currents
Draw and label the diagram
representing seafloor
spreading and subduction
zones
• Basalt
• Granite
• Oceanic crust
• Continental crust
• Divergent boundary
• Convergent boundary
• Mid-ocean ridge
• Trench
• Volcanic arc
• Oldest rock
• Newest rock
• Seafloor spreading
• Subduction zone
• Convection currents
• Mantle
• Magma
Draw and label the
diagram representing
seafloor spreading and
subduction zones
• Basalt
• Granite
• Oceanic crust
• Continental crust
•
•
•
•
•
•
•
Divergent boundary
Convergent boundary
Mid-ocean ridge
Trench
Volcanic arc
Oldest rock
Newest rock
•
•
•
•
Seafloor spreading
Subduction zone
Convection currents
Mantle
Draw and label the
diagram representing
seafloor spreading and
subduction zones
• Basalt
• Granite
• Oceanic crust
• Continental crust
•
•
•
•
•
•
•
Divergent boundary
Convergent boundary
Mid-ocean ridge
Trench
Volcanic arc
Oldest rock
Newest rock
•
•
•
•
•
Seafloor spreading
Subduction zone
Convection currents
Mantle
Magma
On your own piece of paper
Boundaries Tour
Type of Boundary
Location
Crust Type
Subduction?
Volcano?
Earthquake?
Mountain?
Fault Notes
Word
Use the
Orange Textbook
pages 54-57
page 38-39
Definition
stress
deformation
Fault
Hanging wall
Footwall
Word
tension
compression
shearing
Strike-Slip Fault
Normal Fault
Reverse Fault
Definition
Diagram
Faults
• Stress
• Strain
• Compression
• Tension
• Shear
• Fault
– a force that acts on rock
to change its shape or
volume
- a change in the shape of
rock caused by stress
– squeezing stress
– stress that pulls something
apart
– parallel forces acting in
opposite direction
- A break in the Earth’s crust
where slabs of rock slip past
each other
• Shearing, tension and compression work over millions of years to
change the shape and volume of rock
• Any change in the volume of Earth’s crust is called deformation. It
causes the crust to bend, stretch, break, tilt, fold and slide.
Three Types of Faults
Strike-Slip
Thrust (Reverse)
Normal
Hanging Wall
Footwall
• Forms the upper half of
the fault
• Block of rock that forms
the lower half of a fault
Strike-Slip Fault
• Shearing creates strike slip faults.
Rocks on either side of the fault
slip past each other sideways
with little up or down motion
Normal Faults
• Tension forces cause these faults. The
fault is at an angle so that one block
lies above the fault while the other lies
below the fault.
Reverse (Thrust) Faults
• Compression forces. Has
the same structure as a
normal fault, but the blocks
move in the opposite
direction.
Mountain Building
• Over millions of years, fault movement can change
a flat plain into a towering mountain range
•
•
•
•
Form by Faulting
Folding
Anticlines and Synclines
Plateaus
Fault-Block Mountains
• A Mountain that forms
where a normal fault up
lifts a block of rock.
Folding Mountains
• Pushing together of part
of the earth's crust from
the ends, causing it to fold
and ripple in the middle.
Anticline and Syncline
• Anticline – a fold in rock that bends upward
• Syncline – a fold in rock that bends downward in
the middle to form a bow;
Plateaus
• Large area of flat land elevated high above sea
level. Some form when vertical faults push up a
large flat block of rock
Discuss with your partner/neighbor
1. What are the 3 main types of stress in rock?
2. Describe the movements that occur along each of
the three types of faults.
3. How does Earth’s surface change as a result of
movement along faults?
4. If plate motion compresses part of the crust, what
landforms will form there in millions of years?