Plate Tectonics 2015

The Earth is divided into 4 layers.

MANTLE

CRUST

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.

Heat source

Moves up

Heats Up

Cools Down

Moves down

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

1 2 3 4 5 6 7

 Plate Name

Latitudewithin Plate

Longitudewithin Plate

 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      

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 35Plate Motion Data Table

1 2 3 4 5 6 7

 Plate Name

Latitudewithin Plate

Longitudewithin Plate

 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

Page 35Plate Motion Data Table

1 2 3 4 5 6 7

 Plate Name

Latitudewithin Plate

Longitudewithin Plate

 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

Page 35Plate Motion Data Table

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 NotesRead 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

Page 36

Seafloor Spreading NotesRead 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 - mountain range located on the seafloor in the middle of the ocean

•seafloor spreading - new oceanic crust forms at a mid-ocean ridge as - old oceanic crust moves away from the

ridge•magnetic reversal - event in which the magnetic

field reverses direction•normal polarity - today’s magnetic field;

magnets orient themselves to point north

•reversed polarity - magnetic field in - which magnets orient themselves to point south

Process of Seafloor Spreading1. 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

On your own piece of paper

Boundaries Tour

Type of Boundary Location Crust Type

Subduction? Volcano?

Earthquake?Mountain?

Word Definition

stress

deformation

Fault

Hanging wall

Footwall

Fault Notes

Word Definition Diagram

tension

compression

shearing

Strike-Slip Fault

Normal Fault

Reverse Fault

Use the Orange Textbook

pages 54-57page 38-39

Faults•Stress – a force that acts on rock

to change its shape or volume

•Strain - a change in the shape of rock caused by stress

•Compression – squeezing stress•Tension – stress that pulls something

apart•Shear – parallel forces acting in

opposite direction•Fault - 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-SlipThrust (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?