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Chapter 7
Plate Tectonics in Earth History
Chapter Outline:
I.
Origins of Plate Tectonics
a. Continental Drift
b. Seafloor Spreading
II.
Plate Boundaries
III. Mountain Building
Key Terms:
plate tectonics theory
continental drift
seafloor spreading
basins
continental crust
oceanic crust
pangea
glossopteris flora
grabens
aulocogen
guyots
paleomagnetism
hot spots
lithosphere
asthenosphere
divergent plate boundaries
passive margin
subduction zone
convergent plate boundary
transform fault
tectonostratigraphic terranes
orogenesis
ophiolites
foreland basin
clastic wedge
In-Class Activities:
Instructor Notes for In-Class Activity 1
Title:
Alfred Wegener: Pioneer of the theory of Continental Drift
Time:
5-10 minutes prep; 40– 60 minutes in class (or can assign research
between class periods)
Materials:
Internet required. Print worksheets as handouts.
Handouts:
A list of questions for students to research and discuss. Information on
Alfred Wegener and his theory of Continental Drift can be found in the
section of their textbook titled “Origins of Plate Tectonics” and at the
following websites:
http://www.youtube.com/watch?v=bVdrg5ZId1M
http://www.ucmp.berkeley.edu/geology/techist.html
http://pubs.usgs.gov/gip/dynamic/historical.html
http://www.bbm.me.uk/portsdown/PH_061_History_b.htm
Procedures:
Have students review the section “Origins of Plate Tectonics” in the
textbook.
Next, have the students watch the following videoclip:
http://www.youtube.com/watch?v=bVdrg5ZId1M
The students can use the information gained from their textbook, the
video and websites such as the following three to answer the 10 questions
listed below.
http://www.ucmp.berkeley.edu/geology/techist.html
http://pubs.usgs.gov/gip/dynamic/historical.html
http://www.bbm.me.uk/portsdown/PH_061_History_b.htm
1) Did Alfred Wegener believe that the oceans and continents are
permanent features of the earth in steady state? Explain.
2) What is Pangea, and what did Wegener think happened to it according
to his theory of continental drift?
3) List four lines of evidence that Wegener used to support his theory of
continental drift.
4) How did Wegener use the example of a torn newspaper to explain his
theory of continental drift?
5) In the years immediately after the publication of Wegener’s book on
Continental Drift, did most scientists accept or reject Wegener’s theory?
Why?
6) What events led to, and when did the majority of the scientific
community begin to accept Wegener’s theory of continental drift?
7) Did Wegener’s theory of continental drift support or refute the idea of
land bridges being behind the spread of Glossopertis flora more than 200
million years ago?
8) In the years immediately after Wegener’s introduction of the theory of
continental drift, what arguments did the opponents of this theory use to
oppose it.
9) List two types of actual rock evidence used by Wegener to show that
Pangea existed about 200 million years ago.
10) Is Wegener’s suggestion that the continents move by plowing their
way through the ocean floor supported by modern data?
Student
Instructions: See above.
Specific
Suggestions:
The instructor should point out that it was Wegener’s original ideas that
would lead to the eventual formation of plate tectonics theory in the
1960’s. Students should look at the evidence that Wegener used to
support his theory, and the reaction of the scientific community to it in
the early 20th century.
Objectives:
Students should be able to:
Grasp the basic concepts associated with “Continental Drift” theory.
List the original evidence that Alfred Wegener used to support his theory.
List the objections that detractors had to Wegener’s thory.
Describe how Wegener’s work would eventually changed the way
scientists view the continents and oceans.
Describe the history that would eventually lead to the acceptance of
Wegener’s ideas.
In-Class Activity 1: Handout
Alfred Wegener’s theory of “ Continental Drift” was proposed in a book called “ The Origin of
Continents and Oceans” in 1915. The majority of the scientific community rejected or even
ridiculed his ideas. Wegener himself died of a heart attack while trying to cross the ice caps of
Greenland. He never had the opportunity to see how his theory would lead to a revolutionary
change in the way scientists viewed the Earth. This would not happen until the advent of “Plate
Tectonics” theory in the 1960’s. It is important to remember though, that the theory of
“Continental Drift” led to that of “Plate Tectonics” The purpose of this in-class exercise is to
introduce you to Wegener’s theory, to look at the evidence he used to support it, to study the
reaction of the scientific community to his book, and to see how his theory would change the
field of Geology on a grand scale.
First, read the “Continental Drift” section of your textbook, and watch the following video to
gain some knowledge as to the basics of this theory.
http://www.youtube.com/watch?v=bVdrg5ZId1M
Next, use the following websites and your textbook to answer the following questions. Each
member of the group should participate, and the questions should be discussed, and the
consensus answer should be neatly written down on paper. Finally, your answers should be
submitted to your instructor for grading.
1) Did Alfred Wegener believe that the oceans and continents are permanent features of the earth
in steady state? Explain.
2) What is Pangea, and what did Wegener think happened to it according to his theory of
continental drift?
3) List four lines of evidence that Wegener used to support his theory of continental drift.
4) How did Wegener use the example of a torn newspaper to explain his theory of continental
drift?
5) In the years immediately after the publication of Wegener’s book on Continental Drift, did
most scientists accept or reject Wegener’s theory? Why?
6) What events led to, and when did the majority of the scientific community begin to accept
Wegener’s theory of continental drift?
7) Did Wegener’s theory of continental drift support or refute the idea of land bridges being
behind the spread of Glossopertis flora more than 200 million years ago?
8) In the years immediately after Wegener’s introduction of the theory of continental drift, what
arguments did the opponents of this theory use to oppose it.
9) List two types of actual rock evidence used by Wegener to show that Pangea existed about
200 million years ago.
10) Is Wegener’s suggestion that the continents move by plowing their way through the ocean
floor supported by modern data?
Your graded answers will be handed back to you next week. Carefully go over your graded lab
next week to prepare for a test in the near future.
Instructor Notes for In-Class Activity 2
Title:
An introduction to one of the most important scientific theories
introduced during the 20th Century: Plate Tectonics.
Time:
5 – 10 minutes prep; 40 – 60 minutes in class (or can assign research
between class periods)
Materials:
Print instruction sheets as handouts.
Handouts:
A list of questions for students to answer and discuss and recommended
websites. Information pertaining to plate tectonics can be found on the
following websites.
http://www.youtube.com/watch?v=QDqskltCixA
http://www.ucmp.berkeley.edu/geology/tectonics.html
http://www.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html
http://pubs.usgs.gov/gip/dynamic/dynamic.html
http://www.bbm.me.uk/portsdown/PH_063_PlateTec.htm
Chapter 7 in your textbook is also an excellent reference for answering
the questions.
Procedures:
Hand out instruction sheets to students. Using the websites listed above,
and Chapter 7 in the textbook, to answer the following questions.
Where do most of the world’s earthquakes occur? Why?
Where do most of the world’s volcano’s occur? Why?
Where does the energy that drives plate tectonics come from?
What is Rodinia? How did it form, what happened to it?
Briefly describe what may cause the earthquakes and volcanoes
that occur in the middle of plates?
6. Does the magnetic stripe and polar reversal data support Plate
Tectonic theory? Briefly explain.
7. Draw two pictures and briefly describe in words the processes of
sea-floor spreading and subduction.
8. Where is new seafloor being formed, where is it being destroyed?
9. What is a passive margin? Does subduction occur there, how
about earthquakes and volcanism?
10. Who first proposed the theory of seafloor spreading (which would
lead to Plate Tectonic theory), when did this occur?
1.
2.
3.
4.
5.
If time remains, ask the students to discuss how the advent of Plate
Tectonics changed the way Geologists viewed the Earth.
Student
Instructions: See above
Specific
Suggestions:
Objectives:
The instructor should emphasize that student need to become familiar
with the processes of seafloor spreading and subduction.
Students should be able to:
Describe the relationship between plate boundaries, volcanism and
earthquakes.
Describe in pictures and words the process of seafloor spreading and
subduction.
Describe how and where seafloor is formed and destroyed.
Briefly recite the events that led to the formation of Plate Tectonics
theory.
Describe the use of paleomagnetic data in testing Plate Tectonics theory.
In-Class Activity 2: Handout
Prior to the advent of Plate Tectonics theory, scientists knew that we had earthquakes, volcanoes
and mountain building, but they did not know why they occurred in the geographic patterns that
we find them. Also before this theory was introduced, most scientists believed that the
continents and the oceans were permanent features as old as the Earth itself. Plate tectonics
theory is probably the most important scientific theory introduced by geologists in the 20th
century, and entirely changed the way geologists study earth processes. The purpose of this inclass exercise is to study some of the basic principles of this exciting and important theory.
http://www.youtube.com/watch?v=QDqskltCixA
http://www.ucmp.berkeley.edu/geology/tectonics.html
http://www.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html
http://pubs.usgs.gov/gip/dynamic/dynamic.html
http://www.bbm.me.uk/portsdown/PH_063_PlateTec.htm
Using your textbook and the above references, answer the following questions.
Where do most of the world’s earthquakes occur? Why?
Where are most of the world’s volcanoes located? Why?
Where does the energy that drives plate tectonics come from?
What is Rodinia? How did it form, what happened to it?
Briefly describe what may cause the earthquakes and volcanoes that occur in the middle
of plates?
6) Does the magnetic stripe and polar reversal data support Plate Tectonic theory? Briefly
explain.
7) Draw two pictures and briefly describe in words the processes of sea-floor spreading and
subduction.
8) Where is new seafloor being formed, where is it being destroyed?
9) What is a passive margin? Does subduction occur there, how about earthquakes and
volcanism?
10) Who first proposed the theory of seafloor spreading (which would lead to Plate Tectonic
theory), when did this occur?
1)
2)
3)
4)
5)
If time remains, discuss with your other group members how the acceptance of this theory has
changed the way geologists view Earth processes.
Hand in your answers to your instructor for grading. Knowledge of the answers to the above
questions will prepare you both for a future quiz and exam.