Plate Boundaries and Interactions
Name ______Date______Period______
Materials: 2 pieces of 2 x 4” lumber 3 pieces of 4” dowels (any diameter)
Fence diagram (last page)
Procedures:
1. Obtain and assemble the equipment as shown in the following diagram, as follows:
a) Cut the fence diagram in half along the center dotted line. Do not trim excess ends.
b) Staple the left fence piece (#1 on the left) to the lumber as shown in the diagram. Roll up the other end around a dowel.
c) Take the right fence piece (#14 on the left) and roll this end on the dowel leaving enough paper to set up as shown on the right side of the diagram.
2. Use the equipment to model a steady sea-floor spreading and subduction, as follows:
a) One student holds the two rolled-up dowels in one place, loosely, so that they can turn but not shift their position. Another student holds the stapled piece of 2 x 4 lumber “continent” and pulls it away from the rolled-up dowels. A third student holds the dowel and piece of 2 x 4 lumber “subduction zone” at the other end loosely in place. A fourth student pulls the paper strip from under the piece of 2 x 4 lumber “subduction zone.”
b) Be sure to unroll the paper strips at the same rate, so that the numbers of the stripes stay matched up as they appear.
Conclusions:
1. What boundary does the area at the rolled paper strips on the dowels represent? ______
2. What is happening to plates at these types of boundaries on Earth?
______
3. What boundary does the section of paper between the dowels and the continental lithosphere represent? ______
4. What is happening to plates at these types of boundaries on Earth? ______
G
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Extensions:
Use the equipment to model a collision of a spreading ridge and a subduction zone, as follows:
1) Begin with the materials arranged in the same way at the end of Step 1.
2) While two students pull the paper strips to unwind the two rolled-up dowels, the student holding those dowels slides them slowly toward the subduction zone.
3) The student operating the subduction zone needs to make sure that the stripes appearing at the spreading ridge continue to have their numbers matched up.
Questions:
1) What happens to the length of the strip of paper between the dowels and the “continent” side in this situation?
2) What happens to the length of the strip of paper between the dowels and the “subduction” zone?
3) At what “place” does the spreading ridge eventually arrive?
Think about the following questions, predict what would happen, and write a brief answer to each.
4) In the first part of the modeling (Step 2), how long will the ocean on the “subduction” side last?
5) In the second part of the modeling (Step 3), what do you think would happen in real life when the spreading ridge arrives at the subduction zone?
6) In the second part of the modeling (Step 3), how would the ocean on the “continent” side change after the spreading ridge arrives at the subduction zone?
7) In both cases, what do you think would happen in real life if the continent became blocked in its movement away from the spreading ridge by something happening on the other side of the continent?
Reading & Prediction Activity
How Transform Faults Are Formed
When the theory of plate tectonics was young, back in the 1970s, there was an experiment to see how divergent plate boundaries are formed. Scientists might describe this experiment as “beautiful” or “elegant.” It was small enough to be done on a table top. You can run it as a “thought experiment.” A diagram of the setup is shown below. Use a shallow square pan. Fill it with melted wax, and heat the bottom of the pan to keep the wax melted. Cool the surface of the wax with a fan, so that it crusts over to form “lithosphere.” Install roller cylinders along opposite edges of the top of the pan. These two rollers can be rotated outward in opposite directions to pull the solid surface of the wax apart.
Discussion Questions:
1. Predict what will happen to the crust of wax when the rollers are rotated. Assume that everything is perfect (composition of the wax; heating at the bottom; cooling at the top; speed of the rollers).
2. Predict what would happen to the liquid wax below if a break were to occur in the surface wax.
In the actual experiment, the “lithosphere” broke along a crack across the middle of the pan. As the two “plates” on either side of the crack were formed, new “lithosphere” formed as the liquid wax oozed up into the crack and solidified. The amazing thing about the experiment was that the original crack was formed with exactly the same pattern of ridge-crest segments and transform faults that can be seen in the real mid-ocean ridges!
Conclusions:
1. Were your predictions correct?
2. How do you explain any differences between what happened and your predictions?
3. What does the experiment suggest about the age of the transform faults compared to the mid-ocean ridges?
Plate Boundaries on World Maps Activities
Name ______Date______Period______
Look at the world map below, which shows the relative motion of the plates as seen by the RED arrows. Observe what it shows about how the plates move relative to each other.
Analysis:
1. Name two plates that are moving toward each other (colliding/converging).
______
2. Name two plates that are moving apart (diverging).
______
3. Name two plates that are sliding past each other.
______
Materials: Colored Pencils or Highlighters (3 different colors)
Use the world map below to make a map that shows the three major types of plate boundaries.
Procedures:
Remember! Do not outline both of the plates completely; color or highlight only the boundary between the two plates.
1. Use one color pencil or highlighter to color each boundary line that separates two converging plates.
2. Use another color to highlight the divergent plate boundaries, (where plates are moving away from one another).
3. Use a third color to highlight the plate boundaries where plates slide past one another (called transform boundaries).
4. Make a key that shows the color code and boundary type name.
Conclusions: Describe the plate-tectonic setting of your community.
1. How far is your community from the nearest plate boundary? ______
2. What type of plate boundary is it? ______
3. Predict how your community might change its position relative to plate boundaries in the
future? ______
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