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Earth Science Chapter 5
Plate Tectonics
Big Ideas
• Earth’s Interior
• Convection and the Mantle
• Drifting continents
• Sea-floor Spreading
• Plate Tectonics
Earth’s Interior
•How far do you think
it is to the center of
the Earth?
•Almost 4,000 miles!
•The deepest mine in the
world is only 2 miles
• How do you think scientists
know about the center of
the Earth?
• Geologists use 2 main types of
evidence to learn about Earth’s
interior:
–Direct Evidence from rock
samples
–Indirect evidence from
Evidence from Rocks
• Humans have drilled holes and
extracted rock from depths of
12 miles
• Blasts from the Earth have
brought rocks from 100 ft to
the surface
Evidence from Seismic Waves
• Earthquakes produce seismic
waves
• The speed of seismic waves
and the path they take show
the structure of the planet
Three main layers
• The three main layers of
Earth are the crust, mantle,
and the core
• These layers differ in size,
composition, temperature,
and pressure
Temperature
• The first 20 meters beneath
Earth’s crust is cool
• After this depth, temperature
rises 1 degree Celsius per 40
meters
• Heat comes from the molten
layer and radioactive substances
Pressure
•The deeper you go, the
higher the pressure
•This pressure is equal to
that of a swimming pool
Pressure
Lab Skills Activity
• Work with a partner,
• Read the directions to the Lab Zone Skills
Activity
• Create the Data Table on page 129
Crust
• Crust is a layer of rock that
forms Earth’s outer skin
• Crust includes both dry land
and ocean floor
• Crust is very thin compared to
the other layers of Earth, only
5-70 km thick
Crust
Crust
• The crust beneath the ocean is
oceanic crust and usually made of
basalt
• Continental crust consists of
rocks such as granite
• I was very disappointed in the behavior
of some of you on Friday.
• That was extremely disrespectful of you
to run from the classroom when the bell
rang.
• You need to remember that I dismiss you
and not the bell.
• Please take your seat and sit quietly
while you wait for class to begin
Mantle
• The mantle is about 40 km below
the surface
• It consists of a hot, solid rock
• It can be divided into layers
• The mantle is about 3000 km
thick
Mantle
Lithosphere
• The crust and the uppermost part
of the mantle form the
lithosphere
• It is about 100 km thick
• Lithos means “stone” in Greek
Lithosphere
Asthenosphere
• Under increase heat and pressure
• Less rigid-soft like tar, but still
solid
• Asthenes means “weak” in Greek
The Lower Mantle
• Beneath the asthenosphere
the mantle is solid
• This material extends to the
Earth’s core
Lower Mantle
The Core
• Consists of mostly nickel and iron
• Made of two parts, a liquid outer
core and solid inner core
• Together it is about 3486 km thick
• Despite extreme pressure, the outer
core is molten surrounding a dense,
solid inner core
• Evidence suggests that the extreme
pressure in the inner core will not
allow the solid metal to spread and
become liquid
Core
Core and Magnetic field
• Scientists think that movements
in Earth’s liquid outer core create
Earth’s magnetic field.
• This magnetism is what attracts a
compass’ needle towards north
(it aligns with Earth’s magnetic
field)
Individually
• Complete the section 1
assessment on page 131,
including the “writing in science”
assignment. If you do not
complete these in class, they will
become your homework and will
be due tomorrow.
Make a Chart
Types of Heat Transfer
Radiation
Explanation/definition
Conduction
Explanation/Definition
Convection
Explanation/Definition
When you complete the chart
• Read the sections “Convection Currents”, and
“Convection Currents in Earth.”
• 1. Define Convection Currents
• 2. Explain how convection currents work,
using a real example
• 3. Create an illustration of a convection
current
Bellwork
• What are the three types
of heat transfer and give an
example of one that is not
in your book!
Drifting Continents
• http://www.youtube.com/watch?v=WaUk94A
dXPA
Continental Drift
• Prior to Columbus, mapmakers
did not know about the new
worlds
• Shortly after they began to
notice how the coastlines of
several countries seemed to fit
together like a puzzle
Continental drift
• Early 1900s German Scientist
Alfred Wegener made a
hypothesis:
• All of the continents were
once joined together in a
single land mass and have
since drifted apart.
The Origin of Continents and Oceans
• Wegener gathered evidence from
different scientific fields to
support his ideas about
continental drift.
• He studied land features, fossils,
and evidence of climate change
Write a Book!
• Make your own version of Wegner’s book
• Use the same title as he did
• Read pages 138-138 about the evidence he
found
• Create a page for each type of evidence
• Explain how the evidence supports his
hypothesis and include illustrations if
appropriate.
The Origin of Continents and Oceans
• Page 1: Title
• Page 2: Evidence from land
features
• Page 3: Evidence from fossils
• Page 4: Evidence from climate
• Page 5: Conclusion
WHAT DID YOU FIND?
Sea-Floor Spreading
• http://www.youtube.com/watch?v=p0dWF_3
PYh4
Mid Ocean Ridges
Mid Ocean Ridge
• Curve like
seams through
Earth’s oceans
• Most
mountains are
under water,
except Iceland!
Iceland
Hess and Sea-floor spreading
• Harry Hess in 1960 realized that Wegener
was right and the continents were being
moved by sea-floor spreading:
–The sea floor spreads apart along both
sides of a mid-ocean ridge as new crust
is added
–The ocean floors act like conveyor belts
carrying the continents along with
them
Read pages 144-145
Editorial
• You are Harry Hess! (or Harriet Hess)
• You have just concluded your research about
sea-floor spreading
• Prepare a speech for your science conference
in which you will share your findings
• Include your theory, the evidence that
supports if from molten material, magnetic
stripes, and drilling samples, and end with a
conclusive argument!
• http://earthguide.ucsd.edu/eoc/teachers/t_te
ctonics/p_seafloorspreading.html
• http://serc.carleton.edu/files/introgeo/model
s/mathematical/examples/SeaFlrSpreadIpdf.p
df
• http://www.montereyinstitute.org/noaa/lesso
n02/l2la1.htm
Bellwork
• What were the three types of
evidence Harry Hess used to
support his theory of sea floor
spreading?
• http://www.youtube.com/watch?v=q_IYQdKk
WsU
• http://www.youtube.com/watch?v=6CsTTmvX
6mc
• http://maccallum.wikispaces.com/Lesson+15+AN
D+16+Continenetal+Drift+and+Sea+floor+spreadi
ng
• http://www.westerville.k12.oh.us/userfiles/4161
/Classes/9094/Sea%20floor%20spreading%20wo
rksheet.pdf
• http://science.berlinwall.org/files/bhs_science/C
ontinental%20Drift,%20sea%20floor%20spreadin
g%20and%20plate%20tectonics%20PDF.pdf
11-19 Activity
• Open your books to page 148
• We will be completing this lab activity in class
today
• Everyone needs to complete their own seafloor spreading model
• When you complete the model you will
answer the Analyze and Conclude questions
• You may talk to students near your desk about
the questions 1-6
• When you complete the activity,
• Come up with two original questions
from each of the four sections in this
chapter (make sure you can answer
your question)
• I will combine these questions for
your review session tomorrow!
Subduction at Trenches
• Deep-ocean trenches: deep
underwater canyons.
• At deep-ocean trenches the
oceanic crust bends down and
sinks beneath the continental
crust.
Subduction
• Subduction: the process by which
ocean floor sinks beneath the
deep ocean trench and back into
the mantle
• http://www.youtube.com/watch?v=K8J7t3KYr
9c
• http://www.youtube.com/watch?v=wkc4lbhh
SRs
Process of Subduction
• As the older rock is subducted,
younger rock moves away from
the mid-ocean ridge
• New rock is hot, but it cools and
becomes more dense as it ages
Old rock, New Rock, Red Rock,
Green Rock
Process Continued
• Eventually gravity pulls the
older, denser rock down at the
trenches
Subduction and Earth’s Oceans
• Subduction and seafloor spreading
can change the size and shape of the
oceans
• Ocean floor is renewed about every
200 million years
• The Pacific’s trenches are eating
more crust than the ridges can make
• In the Atlantic the opposite is the
case
• http://www.youtube.com/watch?v=hSdlQ8x7
cuk
Review
• http://www.youtube.com/watch?v=_5q8hzF9
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