FAIRLY SIMPLE GEOLOGY EXERCISES
for
STUDENTS AND THEIR TEACHERS
Topics
Fairly Simple Mineral Identification
Fairly Simple Rock Identification
Easy (and Cheap) Crystal Growing
TERRA MOBILIS
John J. Thomas
Purpose
To let the students see for themselves that the continents may at one time have all been one big continent (called Pangaea, (all earth) Figure 4) and may have since separated and moved apart to where they are now creating the present Atlantic Ocean (the theory of plate tectonics). To recreate one of the original experiments that lead to the idea of mobile continents. To show how simple the approach to scientific experiments can be.
Definitions
Plate tectonics - the theory that the rock under the continents and oceans (oceanic crust) is divided up into several (seven major and several smaller) different plates of rock that are moving on the outside of the globe. The continents are being carried along passively on the backs of the ocean plates, thus showing the movement of the oceanic plates.
Oceanic Crust - the outermost layer of planet earth made up of basalt (the material of volcanoes) and about 120 kilometers (75 miles) thick.
Continental Crust - the continents, made up of granitic rock, lighter than basalt so it floats on the oceanic crust.
Ever since the eighteenth century, geologists have been bothered by several geological mysteries. One of the most famous is the fossil record of North America. Paleontologists have known since the middle of the 1800's that the Early Paleozoic rocks of New England and the most eastern part of New York have a completely different fossil fauna and flora than the rest of the continent. The eastern assemblage is distinctly European and bears no resemblance to the western, or North American, communities. The plants and animals are types that could not have swum across the present Atlantic Ocean. How did they get here? There were no birds to carry them and the ocean currents flow from North America to Europe so they did not drift across. The logical conclusion was that the Northeast had at one time been much closer to Europe.
In the early 1900's a German geographer, Alfred Wegener, became fascinated with the concept that North America might have been joined to Europe. He had no idea of how to demonstrate the possibility. Being a geographer, he stared at maps a lot. One day he noticed the striking similarity between the shape of the Americas and the lands across the Atlantic (see Figure 1). Is it possible that they once fitted together? How could one find out? Easy! Cut them out and fit them back together. This is exactly what he did and is what this exercise does.
Optional - An added benefit of this exercise is that you can use it as a geography review. The first part of the exercise can be to review the names and location of the continents. For this activity use Figure 2.
Optional - One of the questions that might be asked is if
the continents are now moving apart, could they also have moved together.
The answer is yes. This phenomenon is called continental collision. Colliding
continents are similar to colliding cars. If two cars run into each other,
they crumple where they meet. The same thing happens with continents;
the crumples are called mountains. If your students are advanced enough,
when you are locating and naming the continents, have them mark in the
Alps, Himalayan Mountains and the Ural Mountains, or use figure 3 as your
base map. The most striking example of continent-to-continent collision
is the Urals. This is the dividing line between what we recognize as Europe
and Asia. They are actually two continents and they have been joined by
collision with the Urals being the result. India is geologically a continent;
it is colliding with Asia creating the Himalayas. Africa is moving northward
pushing Italy into the Alps and the Mediterranean Sea is getting smaller
very slowly.
The Appalachian Mountains (our Taconic, Green and White Mountains) were
caused by the collision that brought the continents together to form the
one big continent, Pangaea, which this exercise will make. Note that all
mountain ranges are related to plate tectonics, but the Rocky Mountains
will have to wait for another exercise for their explanation.
Teaching Aids
For your background a good general reading book on plate tectonics is Basin and Range by John McPhee; Farrar, Strauss, and Giroux, New York. The book appeared as articles in The New Yorker magazine and is written for the layperson. It is, also, a story of McPhee's explorations in the New Jersey and Nevada with two different geologists. It is a very entertaining book, well worth the reading.
There are a variety of videos available to show Continental Drift or Plate Tectonics.
Interesting plate tectonics web pages:
http://www.uky.edu/ArtsSciences/Geology/webdogs/plates/reconstructions.html.
http://www.scotese.com/Default.htm.
http://www.ucmp.berkeley.edu/geology/tectonics.html.
http://www.odsn.de/odsn/services/paleomap/paleomap.html
http://www.odsn.de/odsn/services/paleomap/animation.html.
Materials
Figure 1,2 or 3
Pen or pencil
Scissors
Crayons or colored pencils (optional)
1) Have the students notice that North America and South America look like they could fit against Europe and Africa. Explain that scientists have long been curious about the similarity in shape and wondered if the continents might fit together like a puzzle. Tell them that they are all now going to test if they fit together just like a geographer did in the early 1900's.
2) Name the Continents. (You may have students color them in if you want. This gives the quick students something to do while the others catch up). This is the time at which they should mark in the mountain ranges.
3) Cut the continents out of the sheet of paper. The cutting does not need to be precise. They only have to cut out the approximate outlines.
4) Now have the students fit them together like a jigsaw puzzle. Their arrangement should look like Figure 4.
5) You can then talk to the students about the continents moving apart over the past 70,000,000 years to their present positions.
6) You can have the students move the continents back to where they are now and realize that, at least as a picture, the movement is an easy one.
Let the students take the puzzle home to show their parents.
Go to the top of Teacher Information.
Figure 1. Base Map for Terra Mobilis with Named Continents.
Figure 2. Base Map for Terra Mobilis
Figure 3. Base Map for Terra Mobilis with Mountains.
Figure 4. Position of the Continents after they have been cut out and fitted together.
If you want to do this exercise, all of these maps are full page in the PDF File.
Return to the top of the Student Exercise.
Return to the top of the web page.
An Adobe® Acrobat® PDF® copy of Terra Mobilis is available by clicking on the link.
If you do not have a copy of Adobe® Acrobat® Reader® for PDF® files, click on the link to download a free copy.