Transcript Chapter 10

Plate Tectonics
Evolution of the Earth
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How do we know anything about the Earth
Page 20,22:
Pg. 20
3 Column Vocab
1. Mid ocean Ridge
2. Sea floor spreading
3. Plate Tectonics
4. Asthenosphere
5. Lithosphere
6. Convection cell
7. Pangaea
Pg. 22
8. Subduction zone
9. Rifting
10. Divergent boundary
11. Convergent
boundary
12. Transform boundary
**Not all terms are in
glossary—some are
italicized within the
chapter
How to do 3 column vocab.
Word
Definition
Picture
Page 16
How are scientists able to study the composition
and size of the interior layers of the Earth?
a. By direct observation
b. By analyzing surface rock samples
c. By using seismic waves
d. By deep drilling into the interior layers
Page 16
• Which statement BEST describes how new
scientific views become accepted?
a) A group of scientists come to common
agreement over an idea at the same time.
b) New ideas become a theory when hypotheses
are proven to be correct.
c) When a theory gains so much support it
becomes a scientific law.
d) When observations of our natural world produce
plausible explanations.
In: pg 18,19
• Watch the movie clip “ The Earth’s Interior”
and write down 15 facts.
1.
2.
3.
4.
5.
Use the diagrams below to answer the question.
Page 16
• Which type of plate boundary is shown in the diagram?
a. Divergent
b. Transform
c. Convergent
d. Universal
Page 16
• Prior to Alfred Wegener’s theory of continental
drift geologists thought continents were fixed in
their locations. In developing his theory which of
the following evidence was NOT used by
Wegener?
a) Fossil similarities between southern continents.
b) Evidence of polarity change in found along the MidAtlantic Ridge.
c) Similarities in the paleoclimates of South America
and Africa.
d) The apparent fact the South America and Africa
seemed to fit together.
20
Warm up
Wrap up
21,23,25
Earth’s interior
Chapter 10
Interior
Interior
Thru 1: Pg 21
The Earth’s Interior Questions
• Read the front and complete the questions on
the back.
• Tape in as a flap
Thru 1: pg. 21
Please copy this concept map and then complete it by filling in
one appropriate descriptor at the end of each arrow. Use pages
239-241 in the textbook.
When discovered
Scientist
Definition
Theory of
Continental
Drift
What is missing?
Continents
Supporting Evidence
Fossils
Rock
Climatic
Formations
Quiz #1 Sep. Sheet
1.
2.
3.
4.
5.
6.
7.
Pg. 25 What is the title of Ch. 10?
Pg. 27 What is the answer to #2?
Pg. 27 What is the answer to #10?
Pg. 27 How thick is the core?
Pg. 29 What is the answer to #5?
Pg. 29 What is the answer to #10?
Pg. 31 What was the name of the scientist who
came up with the Theory of Continental Drift?
8. Pg. 31 The Theory of Continental Drift says that
the continents are___________.
Thru 2
Pg. 23-use the
supercontinent on pg. 33 and
the book to answer these
questions.
Analysis Questions:
1. What are 3 pieces of
evidence you used to fit
together the continents?
2. Why is this called a
supercontinent?
3. How does this model
help support the Theory
of Continental Drift?
4. Why aren’t the
continents still in this
location today?
Pg. 25
Supercontinent Cutout.
Cutout the continents
and fit them together to
make the
supercontinent that
Wegener proposed.
Glue them on this page.
Alfred
Wegener
Theory of
continental
drift
• Harry Hammond Hess
Harry Hess commanding the USS Cape Johnson.
• Born May 24, 1906 Died August 25, 1969
Suggested that the convection of the Earth's mantle was the
driving force behind plate tectonics. .
Tectonic Plates
Today plate boundaries are determined by examining
the location of volcanoes and earthquakes.
Volcanoes result from the friction (heat) of the plates
motion.
Earthquakes occur where plate rub against one another
Tectonic Plates
Tectonic Plates
Tectonic Plates
Tectonic Plates
Evidence of Continental Drift
Pangea
• What is Pangaea?
• Pangaea was a super continent at one time.
• Scientists use the similarity of rock types and fossil types that date to the
same age to support their theory that the continents were connected to
form a super continent.
• The map below give just one example of areas on different continents that
show the same fossils and rock types.
Pangea
• Pangea
Tectonic Plates
Evidence
Our first evidence of tectonic motion is based on similar fossils and
rock types on opposing sides of the ocean
Tectonic Plates
Tectonic Plates
Radioactive Dating
Another source of
evidence is based
on seafloor ages
which get younger
as we approach
sea floor ridges
Tectonic Plates
Our final piece of
evidence is the
magnetic record
of the ocean floor.
This shows the
pattern of reversal
and we find a near
perfect mirror image
on opposing sides
of the ridge
Where are we going?
We appear to be headed for another
super continent as North America,
South America, Asia and Australia converge in the
ever shrinking Pacific Ocean
Composition vs. Motion
We can look at the interior of the Earth based
on the composition of the rocks or based on the movement
Based on Composition
• Crust – solid, relatively low density silicate rock
• Mantle – Semi fluid, denser, mafic (iron and magnesium
bearing) rocks
• Core – Liquid then solid iron and nickel with traces of
heavier elements
Based on Motion
• It turns out that the upper section of the
mantle is adhered (stuck to the underside
side of the crust to form what we call
tectonic plates
Plate Types
• Oceanic plates: basalt
– Dark (black) and dense rock
type composed of silicates,
iron and magnesium
• Continental plates – granite
and andesite
– Light colored (pink, white and
gray) and low density rock
type composed almost
entirely of silicates.
Plate Boundaries
• Convergent – plates move toward one
another
• Divergent – plates move away from each
other
• Transform – plate moves sideways from
each other
Plate Boundaries
Convergent Plates
Convergent Plates
Convergent Plates
The only subduction zone
in the Atlantic
Convergent Plates
Black arrows show subduction zones and
the direction of plate movement
• Subduction.swf
ocean-con
ocean-ocean
con-con
Divergent Plates
• Divergent
• sfloorspreading.swf
Divergent Plates
Divergent Plates
Divergent Plates
Transform Plates
• Trboundary.swf
Transform Plates
San Andreas
Fault
Mid-Plate Hotspots
Mid-Plate Hotspots
Mid-Plate Hotspots
Mid-Plate Hotspots
Hotspotvol.swf
Why do the Plates Move?
Why do the Plates Move?
• No single idea explains everything but we can
identify several forces that contribute to the
movement of the plates.
– Slab pull
• The sinking of the cooled dense oceanic plates pulls on the rest of
the plate
– Ridge rises
• The material deposited on the top of the ridge slides downs from
the rise pushing on the plate
– Convection
• Movement within the mantle could be part of the driving force
behind the motion of the plates.
The Big Picture
Volcanoes
• Volcanoes are the result of hot spots within the crust
or mantle of the earth.
• The hot, liquid rock will break through weak spots in
the surface and form volcanoes or flood basalts.
• Many volcanoes do not release lava, instead they spit
ash and small bits of lava called lapilli.
• Some eruptions are quiet with very fluid (low
viscosity) lava flows while others are explosive
Volcanoes
Quiet
lava
flows
Volcanoes
Mt. St. Helen before the explosive eruption
Volcanoes
Volcanoes
Time lapse of the eruption
Volcanoes
Mt. St. Helen after the eruption
Volcanoes
Earthquakes
Tidal waves or Tsunamis result when the low amplitude long wavelength waves
reach the shallow shoreline and begin to feel the bottom of the sea floor. This
Shortens the wavelength and increase the amplitude (height).
Earthquakes
Location of worldwide earthquakes
Tsunami
Ch. 10 Plate Tectonics
Thru 1: pg 35
Cornell Notes
The Theory of Continental Drift
• Continents were once in a single landmass or
supercontinent that drifted apart into the
continents we see today.
– Supercontinent was called Pangaea
• Alfred Wegener came up with the Theory of
Continental Drift in 1911.
• Used the shape of continents, distribution of
fossils and rock formations to hypothesize that
the continents were at one time all together.
• No mechanism until 30 years later.
The Supercontinent
Mid-ocean Ridges
• Undersea chains
of volcanic
mountains that
run along the
ocean floor.
• Have deep
valleys in the
center where
magma comes
up.
Sea Floor Spreading
• The ocean floor is moving outward from the
mid-ocean ridges.
– The rock closer to the ridges is younger than the
rock far from the ridges
– Oceanic rock is much younger than continental
rock.
– Explains how the continents move.
• Magma rises to the surface and solidifies and
new crust forms
• Older Crust is pushed farther away from the ridge
Sea Floor Spreading Animation
Lithosphere and Asthenosphere
• Lithosphere is the rigid
outer layer of the
Earth.
• Made of the crust and
the solid outer layer of
mantle.
• Asthenosphere is the
layer of “plastic” rock
in the lower mantle.
• Flows like a very thick
liquid.
Lithospheric Plates
• Lithospheric Plates-The
rigid lithosphere is broken
into blocks or plates
– Also called Tectonic Plates.
– Float on the semi rigid,
moving asthenosphere.
Tectonic Plates
Theory of Plate Tectonics
• Theory of Plate Tectonics explains how the
lithospheric plates move.
Convection Currents
HOT!!!!
Convection currents caused by the very hot
material at the deepest
part of the mantle rising,
then cooling and sinking
again --repeating this cycle
over and over.
***Remember…this heat is
generated by the core!!
How Plates Tectonic Works
As magma heats up and rises, it exits through the rift in the
middle of the mid-ocean ridge. It cools and pushes the plates
apart. The Asthenosphere is also moving in convection
currents(created by unequal heating), carrying the plates
Now!
• Write 3 questions in the left hand column and
a 3 sentence summary at the bottom.
Out
Tent Paragraph-use the following words
correctly in a paragraph. Highlight the words
within the paragraph.
• Lithosphere
• Asthenosphere
• Tectonic plate
• Convection cell
• The movement of tectonic plates is inferred by
many scientists to be driven by
a. tidal motions in the hydrosphere.
b. density differences in the troposphere.
c. convection currents in the asthenosphere.
d. solidification in the lithosphere.
In: pg. 38
• Use your notes on pg. 35 to answer these questions:
1. Who came up with the Theory of Continental Drift?
2. _______ are undersea chains of volcanic mountains
that run along the ocean floor.
3. ________ spreading explains that the ocean floor is
moving outward from the mid-ocean ridges.
4. The ______is the rigid outer layer of the Earth.
5. The ______ is the layer of the lower mantle that flows
like a thick liquid.
6. The lithosphere is broken into _____ plates.
7. The Theory of ______ ______ explains how the plates
move.
8. The mantle moves in _________ currents created by
the unequal heating of mantle material.
Thru 1: Pg. 39
Plate Boundaries Diagrams
http://geology.com/nsta/
Plate boundaries
Different Types of Boundaries
http://pubs.usgs.gov/gip/dynamic/understanding.html
Divergent Boundary –
Arabian and African Plates
Convergent Boundary – Indian and Eurasian Plates
Convergent Boundary – Oceanic & Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Convergent Boundary – Oceanic & Oceanic
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Convergent Boundaries - Continental
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
Transform Boundary – San Andreas Fault
www.geology.com
Out
When 2 plates converge, one plate will normally
subduct.
• What does the word “subduct” mean?
• What is a subduction zone?
• What determines which plate will subduct?
Wed. 2/27 and Thurs. 2/28
In: pg. 40
• Match the type of
boundary with the
structure that will form.
1. Oceanic/oceanic
2. Oceanic/continental
3. Continental/continental
A. Mountain ranges.
B. Trenches and island
arcs
C. Trenches and volcanic
arcs
Thru 1: pg. 41
• Tectonic Plates Map Worksheet.
– Complete the questions and tape in the
worksheet.
Out
• A friend tells you that California is going to fall
off and Nevada will one day be waterfront
property. Please explain what is wrong about
this statement.
In: pg. 34
• Take the cup at your table to the sink and fill it about ½ full of water.
Return to your table and drop the colored ice cube in the cup. Watch
the water that melts off of the ice cube and draw what you see. Use
arrows to represent the movement of the red water.
1. Did the cold water
coming off of the ice
cube sink or float?
2. Which is more densecold or warm water?
Convection
• When a substance is
heated it becomes less
dense and rises.
• When a substance
cools, it becomes more
dense and sinks.
• This creates a circular
movement in the
material called a
convection cell or
current.