Where Are We Going?

A Look at Plate Tectonics and the Evidence Behind the Theory

By Jennifer Rogstad

 

Powerpoint Presentation

 

Note to Teacher: I have compiled questions for students to think about and answer as they explore fantastic animations, pictures and information on a CD-ROM. The Multimedia CD-ROM is The Theory of Plate Tectonics by Ed Tarbuck and Fred Lutgens Version 2.1 produced by Tasa Graphic Arts, Inc. (See ordering info below) By utilizing the CD-ROM, students have the opportunity to see what is happening with the Earth’s plates and take-in the information at their own pace (within reason of course!). The Theory of Plate Tectonics has excellent questions at the end of each section that the student can even print out. However, I really wanted a set of questions that students could answer as they progress through the CD. My hope is that this will motivate students to look at, read and analyze each slide/frame rather than just flip through the CD until they find the answers to the questions at the end. I recommend that beyond the scope of this lesson you talk about each piece of evidence for the Theory of Plate Tectonics, look at several animations (the animations by Dr. Tanya Atwater are wonderful! Check them out at http://emvc.geol.ucsb.edu/), and explore the continents on maps. Then, at some point during your unit on Plate Tectonics, go to the computer lab where students can answer the questions I have provided below. Oh, and make sure students choose the “Advanced” version on the Table of Contents when they begin the session. I am not sure how long this set of questions will take students to complete since I am not teaching Earth Science this year and have no students to test it out on. I compiled the questions in sections, so you don’t have to assign them all at once. You can print out the questions for students or…however you want to use them!

 

I created a quick PowerPoint with the same info (but without the questions) and with a few pictures that I took near the San Andreas Fault. Other pictures are from the USGS web site at www.usgs.gov and Tanya Atwater’s web site at http://emvc.geol.ucsb.edu. It is a great

site with many more amazing pictures! To check out the pictures I used and others, visit the web site. Click on the “geology” link. Click on the “Search the USGS” heading. Then, in the search box, type in “plate tectonics pictures”. Go to the “Educators page for volcanoes”. Click on “This Dynamic Earth- The Story of Plate Tectonics”. Choose from the “Contents” selections.

 

This lesson addresses the following Grades 9-12 Earth Science Standards:

3a. Students know features of the ocean floor (magnetic patterns, age, and sea-floor topography) provide evidence of plate tectonics.

 

Ordering Information: Obviously, I highly recommend this CD. Again, it is the Version 2.1 Multimedia CD-ROM The Theory of Plate Tectonics by Ed Tarbuck and Fred Lutgens and produced by Tasa Graphic Arts, Inc. The CD also includes animations, pictures and information on Divergent, Convergent & Transform Fault Boundaries, Testing the Plate Tectonics Model, What Drives Plate Motions, and Pangaea: Before And After. The Single User cost of the CD is $59.00 and the Multi User cost is $155.00. (The last time I checked anyway! Double-check on prices.) You can order by phone: 1-800-293-2725 or by internet: www.TasaGraphicArts.com. You can also email for more information on purchasing CDs at info@tasagraphicarts.com.

 

 

 

Where are we going?

A Look at Plate Tectonics and the Evidence Behind the Theory

 

As any good scientist would do, we'll begin by asking a few questions:

How did the mountains get there?

What caused the huge tsunami?

What causes some volcanoes to erupt while others lay dormant?

 

These questions arise when we look around us and question what's going on.

 

For example: Look at the picture. This picture was taken near the San Andreas Fault. What made the rocks in the hillsides curve like that?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


This is caused by movement of the Earth's tectonic plates. The idea that the Earth has plates of material that are actively moving around and changing the shape of our planet was not articulated until 1912 by Alfred Wegener in what is now known as the Theory of Continental Drift. Wegener believed that these plates were once part of one giant supercontinent, Pangaea, which broke apart and allowed the continents to “drift.” Since then it has been determined that the continents are not just “drifting” but rather moving apart due to plate tectonics. Wegener’s theory was, however, instrumental in paving the way for the Theory of Plate Tectonics. The Theory of Plate Tectonics, as proposed by William Ewing and Harry Hess, states that the Earth’s outermost layer is fragmented into a dozen or more large and small plates that are moving relative to one another as they ride above the hotter, more mobile material below. (USGS) In this lesson, we will look at the existing evidence for this theory.  This evidence includes:

 

Fit of the Continents

Fossils

Rocks

Paleoclimatic Patterns

Paleomagnetic Patterns

Sea Floor Topography

 

 

This lesson addresses the following Grades 9-12 Earth Science Standards:

3a. Students know features of the ocean floor (magnetic patterns, age, and sea-floor topography) provide evidence of plate tectonics.

 

 

 

 

The Theory of Plate Tectonics

Questions correspond with the Multimedia CD-ROM version 2.1 (Advanced) written by Ed Tarbuck and Fred Lutgens and published by Tasa Graphic Arts, Inc.

 

I.         Introduction

 

1.         True or False: The Earth is a static, unchanging planet.

2.         Was the Grand Canyon around 200 million years ago?

3.         Was North America closer in location to or farther away from Africa 200 million years ago?

4.         Earth Scientists have shown that the ____________ are ____________ fixed.

5.         What generates earthquakes, volcanoes, mountains and new ocean basins?

6.         What helps explain the distribution of fossils?

7.         Plate Tectonics is the name given to the scientific theory that describes what?

8.         On slide 14, what color is what is now known as North America?

9.         The hypothesis that preceded the theory of Plate Tectonics is known as ____________  ____________.

 

II.      Continental Drift: An Idea Before Its Time

 

1.       Who is credited with the development of the Continental Drift hypothesis? ____________  ____________

2.       Wegener hypothesized that over 200 million years ago there was a ____________ called ____________ meaning “all land.”

3.       Using the down arrow on the keyboard (slide 19), see how the positions of the continents have changed over time (at 0° longitude). Was South America still connected to Africa 130 million years ago? _____ 100 million years ago? _____

4.       What 4 pieces of evidence did Wegener and his colleagues collect to support the Continental Drift hypothesis?

 

Fit of the Continents

 

5.       Wegener thought that ____________  ____________ and ____________ fit together like pieces of a jigsaw puzzle. Why would they probably not fit together perfectly today?

6.       In what year did Alfred Wegener publish a picture of the supercontinent in the 4th edition of The Origins of Continents and Oceans?

7.       Can you fit together the continental shelves of South America and Africa just as the scientists did in the early 1960’s (slide 27)?

 

Fossil Evidence

 

8.       When did Wegener first take the idea of continental drift seriously?

9.       Fossils of the same ancient ____________ and ____________ were found on widely separated continents.

10.   Describe a Cynognathus.

11.   Where were Cynognathus fossils found?

12.   Describe a Lystrosaurus.

13.   Where were Lystrosaurus fossils found?

14.   On which continents has evidence of the plant Glossopteris been found?

15.   Does fossil evidence indicate that the Mesosaurus was able to swim to India?

16.   What 3 ideas were proposed to explain how identical fossils could be found on continents separated by thousands of kilometers of open ocean?

17.   What was Wegener’s explanation for this mysterious distribution of fossils?

 

 

Evidence From Rocks

 

18.   When working with a jigsaw puzzle, what are two requirements?

19.   In the “Continental Drift Puzzle,” rocks must be of similar ____________ and ____________.

20.   Similar 2 billion year old rocks have been found in ____________ and in the ____________  ____________.

21.   The Appalachian Mountains in North America appear to be very similar to mountains in the ____________ Isles and ____________.

 

Pale climatic Evidence

 

22.   Between ______ and ______ million years ago, vast ____________  ____________ covered extensive portions of Earth’s landmasses.

23.   Click on the shovel in slide 52. Where did evidence of this glaciation come from?

24.   What lies below these layers?

25.   Where on the globe is much of the glaciated area found?

26.   Why have scientists rejected the explanation that the equatorial region was once as cold as Antarctica is today?

27.   Click on the shovel in slide 55 and keep clicking on “forward.” Stop when you come to the remains of a plant. What are two characteristics of plants that grow in the tropics?

28.   Click on “return” and then go forward to slide 56. Today, how do scientists explain the location of ancient glaciated landscapes as far North as Green Bay, Wisconsin?

29.   Was present-day India once part of an ice sheet?

 

The Great Debate

 

30.   One critic of Wegener’s hypothesis said that the idea “takes considerable  ____________  ____________  ____________  ____________.”

31.   Go forward to slide 60. What is the Coast Guard Cutter POLAR STAR?

32.   Explain why Wegener was incorrect in his proposition that the continents broke through the ocean floor like an ice breaker cuts through ice?

33.   How much time passed before most of the scientific community accepted the idea that the continents had indeed moved?

 

III.   A Scientific Revolution Begins

 

Continental Drift and Paleomagnetism

 

1.         Why did people become interested in continental drift in the early 1050’s?

2.         Do the Earth’s magnetic and rotational poles line up exactly?

3.         Explain how a compass works.

4.         What is a “fossil compass”? Give one example.

5.         Give an example of a mineral with a lot of iron in it.

6.         Where is the iron-rich basalt flow of the Columbia River located? (click on the globe at the bottom, left-hand corner of slide 92)

7.         When lava with basalt in it cools, what happens to the iron-rich mineral grains?

8.         What is paleomagnetism?

9.         How does the present-day North Pole compare with the magnetic pole of 400 mya?

10.       Explain “polar wandering”.

11.      What is another possibility for the change in location of magnetic poles?

12.      What explanation best accounts for polar wandering?

13.      So, do some scientists think that the poles have moved? Or is it the continents that have moved?

14.      Are the migration paths of the poles more similar today or when the continents were together as one supercontinent?

 

Seafloor Spreading

 

15.      What new technology enabled scientists to gain a better understanding on the ocean floor?

16.      How can an echo sounder find out a particular water depth?

17.      What is your answer to the question on slide 118?

18.      Look at the data table on slide 121. What is the depth in meters at point 10?

19.      How is a profile of the ocean floor constructed?

20.      Once you plot points 12-22 on slide 123, does the profile rise at around 2900 km or does it remain flat?

21.      What do you notice about the middle of the profile of the ocean floor from New England to North America?

22.      What do we call this rise in seafloor?

23.      What was discovered at the middle of this rise in seafloor?

24.      What are 2 characteristics of the oceanic ridge system?

25.      Click inside the box to view the movie on slide 130. What is happening to the blue oceanic floor?

26.      What else was discovered by mapping the ocean floor?

27.      Is the ocean floor relatively young or old?

28.      This information was used to create which hypothesis?

29.      What effect do the convection cells in the mantle have on the seafloor?

30.      How is new oceanic crust created?

31.      What happens to older parts of the seafloor?

32.      So why is the ocean floor so “young”?

 

 

IV.  Plate Tectonics: The New Paradigm

 

1.         Plate tectonics is a theory that includes ideas from which two concepts?

2.         The stiff lithosphere is made up of the ____________  ____________ and the ____________.

3.         The asthenosphere is located in what layer of the earth?

4.         What allows the Earth’s rigid outer shell to move?

5.         The Earth’s plates are part of the ____________.

6.         How many major lithospheric plates are there? Name one of them.

7.         How is our knowledge of the plates today different from that of Wegener’s when he proposed the continental drift hypothesis?

8.         Are there smaller, intermediate-sized plates?

9.         On which plate is the West Coast of the U.S. on?

10.      Does one plate affect another plate when it moves?

11.      Why does most of the earthquake activity, volcanism and mountain building take place at plate boundaries?

12.      List the 3 types of plate boundaries.

13.      What is the symbol for a divergent boundary?

14.      Which plate is growing larger?

15.      Which plate is shrinking?

16.      Which plate may eventually split into 2 plates as a result of a divergent boundary?