Floating Plates

Object of the Activity

Read about, then demonstrate, tectonic phenomena and events involved in the creation of the Aleutian range. Teach your classmates the concept assigned to your group.

Search the hot links on the Internet to learn about the tectonic concepts assigned to your group. Then, follow the directions for your group to create a demonstration model to use in your teaching presentation. Note: After your presentation, be prepared to answer the following questions in class.

• If you could "fast forward" the events that took place from the movement of the Aleutian Terrain to the explosion of Mt Novarupta, what would you expect to see and hear?
• How would the atmosphere be affected?
• What would be happening to the ground on which you would stand?

Steps to Follow:

Use the attached Hot Links to help you learn about the topic assigned to your group.

Before you begin, assign roles to group members. Base these roles on the things you must do to complete the demonstration. Choose a team captain and a team secretary.

Read all the directions for creating your presentation and discuss the best way to use the demonstration to explain the assigned topic.

Discuss ways to make your presentation eye-catching and memorable.

Practice with the person or persons assigned to make the actual presentation to the class. Include in your presentation a connection to the actual tectonic events that formed the Aleutian Mountain ranges as described in the video.

Resources/Materials/Supplies

Video Segment

Per small group:

Internet access

Supplies for Group 1:

• 1 large sheet of poster board
• 250 ml of dried beans
• 250 ml of paper clips
• 250 ml of pennies
• 250 ml of raisins
• glue
• scissors

Supplies for Group 2:

• 1 large sheet of poster board
• 2 sheets paper 14 x 21 cm
• scissors
• tape
• crayons

Supplies for Group 3:

• 6 large chocolate bars, 3 each of 2 different densities (For example: Hersheys plain, solid chocolate bar and a 3 Musketeers Bar)
• paper
• pencils or markers

Working Tips and Hints

Be sure you sign up for time working at a computer that has Internet access. If possible, divide the work among group members and use computers at home.

Group 1: Evidence of Continental Drift by Matching Shape, Rocks and Fossils

Demonstrate the evidence for continental drift. Cut the largest circle you can out of the poster board.

Glue beans, raisins, paper clips and pennies to the circle in overlapping sections.

Cut the circle into 5 or 6 irregularly shaped pieces so that only 2 or 3 pieces contain the same combinations of "toppings."

When using your model to demonstrate continental drift, think of each piece as continents that began welded together, much as Pangaea is imagined. The continents separated as the plates moved, carrying rocks and animal and plant fossils with them. You can see by their shape, as well as by the "rocks and fossils," how the continents began and how they have moved.

Separate the pieces of the model and show them around the room. Ask other students to help you put the pieces together again, while you explain the connection between the model and the drifting continents.

Plan how you can use the model to demonstrate the plate that led to the formation of the Alaskan peninsula, as described in the video.

Group 2: Evidence of Plate Movement through Sea Floor Spreading

Demonstrate the phenomenon of sea floor spreading. Cut a slit 14 cm lengthwise in the center of the cardboard rectangle, representing the ocean floor.

Stick both pieces of paper (the 14 cm edge) up through the slit so that about 5 cm show above the cardboard. These sheets of paper represent magma rising up through a crack in the ocean plate.

Fold both sheets downward away from each other and smooth them out flat against the surface of the cardboard.

Color both strips of paper above the slit. Show rocks and fossils on the strips.

Repeat the procedure, using a different color, pulling the paper up about 5 cm each time.

Show different types of rocks and fossils on each sheet. Hint: If you want to be truly accurate, find information in either texts or encyclopedias or the Internet about the different kinds of animals that developed over time in the oceans. Use this information on your paper strips.

As the strips spread out from the slit in the cardboard, you are demonstrating the slowly spreading sea floor. Rocks farthest away from the rift or split in the ocean floor are the oldest. Magma flowing up through the edge of the rift hardens onto the plate edges and pushes the plates apart. As time passes, magma continues to rise, filling the rift, hardening and moving outward.

Determine the best way to use your model to explain the importance of sea floor spreading to the theory of plate tectonics.

Group 3: Evidence of Plate Movement on the Planet's Surface

Use the Internet resources to discover the 3 different ways in which the plates moved relative to each other and the results for the Earth's surface.

Be sure you know which one is more dense, oceanic or continental plates.

Demonstrate the 3 kinds of plate interaction using different density candy bars.

•  Divergent Movement: Occurs when plates move apart, such as when the sea floor spreads. Group 2 will model this.
•  Convergent Movement: Occurs when plates butt up against one another.
•  Transform Movement: Occurs when plates move roughly parallel to each other in opposite directions.

First use the paper and pencil to draw 2 charts each with 2 rows and 2 columns. Label one column Continental and one column Oceanic; label one row Continental and one row Oceanic.

The first of these 2 charts should be titled: Convergent Plate Movement and the second Transform Plate Movement.

Divide your chocolate bars according to their density. That is, the heavier, solid bars will represent continental plates; the less dense bars will represent oceanic plates. You will use these to simulate plate movement.

• Convergent Plate Movement Simulation
  1. Place 2 dense chocolate bars (continental plates) end-to-end on a flat surface. Push them together and observe what happens. Hint: They should crumble upward where the bars meet. This is called uplift and where it occurs you can find mountains in an "uplift zone."
  2. Repeat this with 2 of the less dense bars (oceanic plate).
  3. Sketch the results in the chart labeled Convergent Plate Movement. In the box where the Continental column and the Continental row meet, draw a picture of the 2 dense bars converging. In the box where the Oceanic column and the Oceanic row meet, draw a picture of the 2 less dense bars converging.
  4. Repeat Step 1 with one dense bar and one less dense bar. What happens? Hint: The dense bar should rise over the less dense bar. The tendency for the less dense plate to dive under the dense plate is subduction. At these points, the heat and pressure of the subduction creates magma and, sometimes, results in a volcanic explosion.
  5. Record this in the appropriate space on the matrix.

   

• Transform Plate Movement Simulation
  1. Place 2 dense chocolate bars (continental plates) side by side, touching.
  2. Slide the 2 bars in parallel, opposite directions, sides touching. What happens to the edges of the bars? What would happen if the bars edges were rough and not straight? Explain.
  3. Record the results in the Transform Plate Chart where the Continental Column and Row meet.
  4. Repeat Steps 1 and 2 using two less dense chocolate bars (Oceanic plate) and one dense and one less dense bar. Repeat the experiment after using scissors to make the bars edges less even.
  5. Record the results of each experiment in the appropriate square on the Transform Plate Chart. Note: The area where the two plates meet and slide against each other is called a fault zone.