Download Structure of the Earth - South Kingstown High School Home Page

Plate tectonics
Notes
Drilling into the mantel: NPR article
Radio program
http://www.npr.org/2011/03/25/134855888/
Drilling-To-The-Mantle-Of-The-Earth
 Video:
http://www.sciencefriday.com/program/arc
hives/201103253

Structure of the Earth

Mantle
The Earth is
made up of 3
main layers:
Outer core
Inner core
 Core
 Mantle
 Crust
Crust
Inner Core
 center
of the Earth
 made of iron and nickel
 that is in a solid state,
 1200 km thick
Outer Core
Surrounds the inner core
 liquid iron and nickel
 2270 km thick
 Liquid is in constant motion
 Moving electric charge
creates the Earth’s
magnetic field

http://oceanexplorer.noaa.gov/explorations/05galapagos/logs/dec22/media/magfield_600.gif
Mantle
between the outer core and crust
 Mafic composition: means made
of heavy elements like iron,
magnesium, and silicon (ex:
basalt rock)
 2900 km thick.
 The asthenosphere is the layer
of the upper mantle that is made
of rock that is partially melted.

Crust




outermost layer of the earth
Felsic composition: means
made of lighter elements
(example: granite rock)
10 km at ocean basins, and
65 km thick below the
continents.
Lithosphere is made of the
upper part of the mantle and
the crust. The lithosphere is
a solid that is broken in
pieces (tectonic plates).
Cross Section of the Earth
Alfred Wegener: German Scientist who proposed the
theory of continental drift.
Continental Drift: All continents were once a part of a
single supercontinent and they’ve moved
Wegener 1930
launching weather
balloon in the
arctic.
http://www.pbslearning
media.org/resource/ess
05.sci.ess.earthsys.weg
ener1/plate-tectonicsthe-scientist-behindthe-theory/ video about
Wegner 4 minutes
Continental Drift
Evidence to support theory of continental drift
1. The shapes of many
continents look like they are
separated pieces of a jig-saw
puzzle.
Picture above from this website to visit:
http://www.sio.ucsd.edu/voyager/earth_pu
zzle/puzzle_together.html
Evidence to support theory of
continental drift
2. the rock types and fossils found on multiple
continents match suggesting the populations once
lived on a continuous
land mass


Website to visit:
http://www.sio.ucsd.edu/voyager/earth_puzzle/earth_puzzle_main/fossils/fossils.html
Continental Drift was not quickly
accepted by scientists because:

Wegner did not have a supported
explanation for how the continents move
and what provided the energy source to
move them.
Answers to Wegener’s opponents
lead to Theory of Plate Tectonics
The plates move because the crust is
divided into separate pieces: tectonic
plates also called lithospheric plates
 These plates are in motion over the
liquid-like asthenosphere.
 The asthenosphere moves due to
convection currents in the lower mantle

Cold
rock is
brittle
Hot rock is
plastic
Very Hot
rock is
Melted
What’s happening in the
asthenosphere?

Convection currents and they are moving
the lithosphere above!
Convection currents & plate movement
“Plates” of lithosphere are moved around by
convection currents in the underlying hot mantle
http://www.earth4567.com/talks/plates/plates.ppt#265,11,Plate Movement
Extra diagrams Sea Floor and Convection Currents
Convection inside the mantle
The source of heat driving the convection
currents is radioactivity deep in the Earth’s
mantle.
PROCESS
 Heated asthenosphere is less dense then its
surroundings so it rises.
 Once it gets close to the earth’s surface it cools,
becomes more dense so it sinks.The more
dense material then sinks
 The process continues forming a circular pattern
called a CONVECTION CURRENT

Convection current definition
PROCESS
 Heated asthenosphere is less dense then
its surroundings so it rises.
 Once it gets close to the earth’s surface it
cools, becomes more dense so it sinks.
 The process continues forming a circular
pattern called a CONVECTION CURRENT
Observe an animation of
convection in the mantle.
Convection current simulations
http://education.sdsc.edu/optiputer/flash/c
onvection.htm
 simulation of convection in the mantle:
http://www.classzone.com/books/earth_sci
ence/terc/content/visualizations/es0805/es
0805page01.cfm?chapter_no=visualizatio
n
 http://earthguide.ucsd.edu/eoc/teachers/t_t
ectonics/p_convection2.html

Good web site not yet used
 http://www.indiana.edu/~g105lab/1425cha
p13.htm

How do we know that tectonic
plates are moving due to
convection currents in the
asthenosphere?

One piece of evidence is preserved in
rocks of the ocean floor!
The ocean floor

Draining the oceans simulation:
http://www.classzone.com/books/earth_sci
ence/terc/content/investigations/es2301/es
2301page03.cfm
Features on the Ocean Floor
Henry Hess and Graphing activity
Sea floor spreading

Animation:
http://www.uwsp.edu/geo/faculty/ritter/glos
sary/S_U/sea_flr_spread.html
Demonstration to do before sea floor spreading lab
WHAT DOES A COMPASS DO
WHEN PUT CLOSE TO A
PIECE OF ROCK THAT
CONTAINS A LOT OF IRON?
Explain how igneous rock can record information regarding the
direction of the Earth’s magnetic field.
• Magnetic rock contains iron atoms.
• Iron will freely rotate when it is magma.
• Each atom acts like a tiny magnet aligning
itself north and south with the earth’s
magnetic field.
• When the magma cools it preserves a
record of the earth’s magnetic field at the
time the rock was formed
Magnetic reversals
Earth’s magnetic poles have reversed
several times in the past.
 Evidence for this is seen in bands of
igneous rock on the ocean floor.

http://www.answersingenesis.org/assets/images/articles/am/v2/n2/figure-2-c.jpg
Sea floor spreading lab

http://www.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.wegener2/plate-tectonics-further-evidence/
video 2 minutes

http://www.edumediashare.com/media.php?id=1325 moving
animation of sea floor spreading with compass
http://novella.mhhe.com/sites/dl/free/0078746361/561688/129_age_ls_170c.gif
Convection currents cause sea
floor spreading
http://www.bcscience.com/bc10/images/0_quiz-12.2-03.jpg
Sea floor spreading




Magma rises along a rift valley in the ocean floor
where 2 oceanic plates are diverging from one
another.
The magma forms new igneous rock.
Magnetic minerals in the rock record the
magnetic field at the time it was formed.
Bands of magnetic rock along the mid ocean
ridge show an alternating pattern of magnetic
poles indicating new rock has been formed as
the earth’s magnetic field has changed.
Earth’s magnetic field: What’s
happening in the core?

The moving metal core creates the earth’s
magnetic field
Electricity and magnetism review
Earth’s magnetic field
Movement of molten iron
and nickel in the Earth’s
core generates electrical
and magnetic fields that
produce Earth's
magnetism.
 The movement of the
metal and therefore
magnetic field has

http://www.windows2universe.org/earth/Magnetosphere/earth_magnetic_field.html
Background for seafloor spreading:
Earth’s magnetic field
Electricity charge, magnetism powerpoint
 Earth's Inconstant Magnetic Field radio
article
http://science.nasa.gov/sciencenews/science-atnasa/2003/29dec_magneticfield/
 Magnetic storm video

Electric Charge
Magnetic fields
Electromagnetic Forces
Electricity and magnetism review
An objects electric
charge depends on
the imbalance of its
protons and
electrons



Negatively charged objects:
more electrons than protons.
Positively charged objects:
more protons then electrons


Protons and neutrons normally remain in the
nucleus
Electrons are easily transferred from one atom
to another
The direction in which electrons are
transferred depends on the materials
Ion (has to do with electrons)

Ion: An atom that has
an unequal number of
protons and electrons.

Example: Lithium

3 (+) protons and 3 (-) electrons



Ions have a positive or
negative charge
Atoms that have a
neutral charge are not
ions

Neutral – no charge
3 (+) protons and 2 (-) electrons

+1 charge – positive ion
Electricity and magnetism review
Like charges repel ( +,+ or -, -)
Opposite charges attract (+, -)
Electricity and magnetism review

Demonstration: Rub balloon on hair
 Compare

Like charges or opposite charges? How do you
know?
 Compare

the charge of a balloon and hair
the charge of two balloons
Like charges or opposite charges? How do you
know?
Electricity and magnetism review
Charged particles produce an
electric field in the space around it.
http://downloadanswer.com/images/ab_Electricity7.JPG
Electricity and magnetism review
Electric field between two charges
http://downloadanswer.com/images/ab_Electricity7.JPG
Electricity and magnetism review
The strength of the electric force
depends on two factors
The distance between charged objects
As distance decreases force increases
 The amount of charge of the objects
The greater the charge the greater the
electric force

Electricity and magnetism review
All magnetic fields are the result of
moving electric charges.
The Invisible World of Magnetic Fields
http://www.windows2universe.org/spaceweather/info_mag_fields.html
Electricity and magnetism review
Magnets are sources of magnetic
fields. The forces can be
illustrated with magnetic field
lines.

Demonstration of field lines with
iron fillings on magnet
Electricity and magnetism review
Bar magnet with iron fillings
http://www.stmary.ws/highschool/physics/home/notes/electricity/magnetism/intro/MagnetFilings.png
The force of magnetism coming from the magnet is called
the "magnetic field", and is illustrated by lines. The magnetic
field is strongest where the lines of force come together (and
turn red), and is weakest when the lines of force are far
apart (and turn blue).
Electricity and magnetism review
http://www.windows2universe.org/physical_science/magnetism/magnetic_field.html
Electricity and magnetism review
Demonstration with iron fillings
in cylinder
http://www.collectibles-articles.com/antique/collectible-image-large/3-d-magnetic-field-demonstrator-iron-filings-magnet_400034425478.jpg
Geographic north vs Magnetic North

Earth's magnetic field
is slightly tilted with
respect to the planet's
spin axis; there is
currently a difference
of about 11° between
the two.
http://science.nasa.gov/science-news/science-at-nasa/2003/29dec_magneticfield/
Electricity and magnetism review
Electromagnet

1.
2.
3.
Directions:
Wind the wire around the nail. Hold insulated wire with
the ends against the batter terminals
Move compass/or paperclip toward the nail to
determine whether the nail is magnetized.
Switch connections to the battery so the current is
reversed. Bring the compass/or paperclip toward the
same part of the nail.
Video about electromagnetic crane:
http://www.youtube.com/watch?v=6yhNOX
QkMpY
Electricity and magnetism review
Earth as an electromagnet

Moving electric charge creates a
magnetic field.
A battery can cause a moving
electric charge in a metal wire
wrapped around a nail. This
creates a magnetic field around the
nail.
 The moving metal in the earth’s
core causes moving electric charge
that creates a magnetic field around

Electricity and magnetism review
Extra slides

When two magnets are brought together, the force
will attract the two magnets together if the poles are
opposite, that is if the pole of the first magnet is
positive and the pole of the second magnet is
negative. If that condition is true, the two magnets
will be "forced" to stick together.

If two magnets of the same polarity are brought
together, the force of magnetism will repel the two
magnets from each other, and they cannot be made
to stick together.
http://www.sciencetech.technomuses.ca/english/schoolzone/Information_Magnetic.cfm#whatare
http://www.windows2universe.org/physical_science/magnetism/force_of_magnetism.html
Electricity and magnetism review
(Background information)
Magnetic field’s importance to humans:
Earth’s magnetic field deflects some of the
harmful radiation from the sun (solar winds)
http://www.ngdc.noaa.gov/geomag/icons/solarexp.jpg
Notes of the Earth’s Magnetism






The Earth’s magnetic pole and geographic pole
are 2 different places.
The geographic pole is the axis for the rotation
of the planet.
The Earth’s magnetic pole changes. It is
currently in Northern Canada. It has completely
reversed at different times in the Earth’s history.
The magnetic pole is caused by the movement
of the liquid metallic outer core.
The Earth’s inner core is a solid ball of iron and
nickel that spins faster then the planet itself.
The Earth’s outer core is a “ocean” of liquid
metal that moves and even has swirling
sections, similar to a hurricane
Theory of Plate Tectonics
 The
Earth’s crust
is divided into 12
major plates
which are moved
in various
directions.
Evidence to support the Theory of
Plate Tectonics
1.
2.
3.
4.
The shapes of many continents fit like
puzzle
Fossil evidence
Seafloor spreading showing magnetic
reversals
Location earthquakes and volcanoes
4. There are a large amount of
earthquakes & volcanoes along
the plate boundaries.
Pacific Ring of Fire
Volcanism is
mostly
focused at
plate
margins
Plate Tectonics
This plate motion causes them to collide,
pull apart, or scrape against each other.
 Each type of interaction causes a
characteristic set of Earth structures or
“tectonic” features.

TYPES OF PLATE MOVEMENT
& FEATURES THEY CREATE
Three types of plate boundary

Divergent

Convergent

Transform
http://www.earth4567.com/talks/plates/plates.ppt#268,14,Slide 14
http://www.eoearth.org/files/164501_16460
0/164590/mid-ocean-ridge-1.gif
Website simulation of Plate
movement
Plate Tectonics: The Scientist Behind the Theory
http://www.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.wegener1/platetectonics-the-scientist-behind-the-theory/

Plate Tectonics: An Introduction
http://www.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.plateintro/platetectonics-an-introduction/

Plate Tectonics: Further Evidence
http://www.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.wegener2/platetectonics-further-evidence/

Mountain Maker, Earth Shaker
http://www.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.shake/mountainmaker-earth-shaker/

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es
0804page01.cfm?chapter_no=visualizationb

1. What kind of boundary is this?
______________
__
________
________
__divergent__________ boundary
2. What is being formed on the earth’s
surface at this plate boundary?
New crust is being formed called mid ocean
ridge mountains.
3. What is the deep crack called? rift____
____Valley_________
1.
What kind of boundary is
this?
________________ Boundary
______________
__
______________
__
2. What type of plates are
interacting here?
______________
__
______________
__
______________
__
3. How does the density of the
ocean plate compare to the
continental plate?
4. Which plate subducts?
5. What happens to the sinking
plate as pressure increases and
temperatures rise?
1. What kind of boundary is this?
_______________ boundary
_______________
_
2. What type of plates are interacting here?
____________- ____________________
3 . How does the density of the two plates
compare?
4.. Why doesn’t one plate subduct underneath
the other?
5. What kind of surface feature is formed at
this boundary?
1. What kind of boundary is this?
_______________ boundary
2. When the movement does not happen
smoothly what happens?
Divergent Boundaries

Spreading ridges
 As
plates move apart new material is erupted to
fill the gap
http://www.earth4567.com/talks/plates/plates.ppt#269,15,Slide 15
Iceland: An example of continental rifting

Iceland has a divergent
plate boundary running
through its middle
Information about Iceland
http://www.platetectonics.com/oceanfloors/
iceland.asp
 http://www.platetectonics.com/book/page_
10.asp Surtsey Island

Convergent Boundaries

There are three styles of convergent
plate boundaries
 Continent-continent
collision
 Continent-oceanic crust collision
 Ocean-ocean collision
Continent-Continent Collision

2 plates of similar density. Forms mountains,
as the edges of each plate push together and
rock accumulates in the middles. e.g.
European Alps, Himalayas
Himalayas
Continent-Oceanic Crust Collision
Called SUBDUCTION
 Continental plate less dense, oceanic
plate more dense

Subduction




Oceanic plate subducts
underneath the continental
plate forming a trench where
they meet.
Oceanic plate heats up and
dehydrates as it goes down
The melted rock rises
through the continental plate
forming volcanoes
Example: The Andes mountains
Ocean-Ocean Plate Collision



When two oceanic plates collide, one runs over the other
which causes it to sink into the mantle forming a
subduction zone.
The subducting plate is bent downward to form a very
deep depression in the ocean floor called a trench.
The worlds deepest parts of the ocean are found along
trenches.

E.g. The Mariana Trench is 11 km deep!
Transform Boundaries



Where plates slide past each other
Often cause earthquakes,
Surface features: sometimes form long linear features like gulley’s
Above: View of the San Andreas
transform fault
Plate Tectonics Summary






The Earth is made up of 3 main layers (core,
mantle, crust)
On the surface of the Earth are tectonic
plates that slowly move around the globe
Plates are made of crust and upper mantle
(lithosphere)
There are 2 types of plates (oceanic, continental)
There are 3 types of plate boundaries
Volcanoes and Earthquakes are closely
linked to the margins of the tectonic plates
EXTRA SLIDES NOT USED
2013-14
Plate boundaries quiz (
A
B
white text)
C
1. Which diagram shows a convergent boundary?
2. Which is a divergent boundary?
3. Which is a transform boundary?
http://www.mhhe.com/physsci/astronomy/fi
x/student/chapter8/08f21.html
A
B
C
4. Which forms trenches? B
5. Which forms a spreading ridge? A
6. Which form volcanic mountain ranges? B
7. Which show subduction? B
8. Which show new rock being formed?
9. Which form a rift valley? _____
A
Pg 235 Questions
1. What is Plate Tectonics?
a. What is plate tectonics? The study of the
formation and movement of the plates that make
up the lithosphere.
b. Identify the plates that are moving apart: RIDGE
with a RIFT VALLEY (African plate and South
American)
(North American and the
Eurasian plate)
moving together or colliding: TRENCH
(Nazca plate and South American plate)
sliding past each other: FAULT
(Pacific and North American)
2.
a. Describe the structure and properties of
the lithosphere. The lithosphere is made
of solid rock. It makes up the crust.
b. How are the composition and density of
continental crust different from that of the
rest of the lithosphere? The continental
crust is made of mostly granite and is
less dense then the oceanic crust which
is made of mostly basalt.
3.
a. Where is the asthenosphere? The upper mantle
/ below the solid lithosphere. A layer within the
mantle that is thought to cause plate
movement.
b. What is the major property of the
asthenosphere? It can move very slowly
because it is “partially melted”.
c. How do the lithospheric plates move where
convection currents are rising? Apart, new
material comes to surface.
d. How do the plates move where convection
currents are sinking? Together
Geohazards and plate boundaries
Location
Earthquakes
Volcanoes
Boundary
type
Peru
++
+++++
Convergent
with
subduction
Kuril Islands
near Japan
+++++
+++++
Convergent
with
subduction
San Andreas +++++
Fault near
San Francisco
Transform
Iceland
+
+++++
Divergent
Aleutian
Islands
+++++
+++++
Convergent
Himalayan
Range
+++++
+
Convergent
Contients
New Zealand
++++
++++
Transform
Conclusion