Unit C: The Dynamic Earth

What causes a volcano to become extinct?

1. Get Set to Explore

Vocabulary

  • extinct: No longer active.

Building Background

  • You may wish to introduce the simulation with a demonstration volcano, made of clay or papier maché. The strato (explosive) volcano could be filled with confetti in a funnel that has an air tube attached to the narrow end. The shield volcano could have a jar containing some baking soda to which you add a mixture of vinegar, dish detergent, and red food coloring for the bubbling-over effect. After the demonstration, ask the class to contrast the two types of volcanoes you demonstrated. Explain that in the simulation, they will learn how these two types of volcanoes differ geologically.
  • Review the vocabulary word. Ask students what they think an extinct volcano is. Guide them to realize that an extinct volcano is one that is no longer active.
  • Pose the Discover! question and have students propose possible answers in a class discussion. Write their answers on the board to refer to later.

2. Guide the Exploration

  • Direct students to launch the Discover! Simulation. They should spend some time watching the animation of the strato volcano and the hot spot volcano.
  • Point out that students can review definitions of any of the terms used in the simulation by moving their cursor over the labels in the diagram.
  • Before students do Step 3 of the simulation, return to the Discover! question. Let students explain what they think causes some volcanoes to become extinct. Have them add to, revise, or correct their previous answers on the board.

3. Review/Assess

  • Have a volunteer read Step 3's Wrap-up text aloud. Show students how the Wrap-up text helps answer the Discover! question: A volcano forms right over a hot spot, but as the tectonic plate that the volcano is on moves, the volcano moves, as well; when the volcano is no longer over the hot spot, it becomes extinct.
  • Present the Extension question: What are some other natural disasters that might be caused by the moving tectonic plates? Lead a class discussion for students to generate answers. You can refer them to Student Edition page C52–C57 for more information. Help students understand how the following natural disasters can be caused by the movement of tectonic plates:
    • violent volcanic eruptions
    • lava flows and forest fires from lava flows
    • earthquakes
    • tsunamis
    • landslides, mudslides, and avalanches
    • flooding or drought related to disruption in normal weather patterns

If time permits, present students with the following questions and activities:

  • Critical Thinking Analyze Hawaii is a chain of islands. The islands that form the southeast part of the chain have active volcanoes. Those that form the northwest part of the chain have extinct volcanoes. Based on this information, where in the chain do you think the hot spot is and which way do you think the tectonic plate Hawaii is on is moving, relative to the hot spot? Answer: The hot spot is under the southeast portion of the chain of islands; the plate is moving northwest relative to the hot spot.
  • Inquiry Skill Use Models Use modeling clay, cardboard, foam blocks, and possibly other materials to make models of a plate moving over a hot spot and of plates moving at a convergent boundary. Refer to books or Internet sources, if necessary, to get details. Use each model to show how volcanoes form and how the plates move. Answer: The model of the hot spot should include a stationary source of magma with the plate moving over the source. The model showing a convergent boundary should include one plate bending under the other plate. The volcanoes form on the plate that is not being subducted.

4. Reaching All Learners

Challenge

Challenge interested students to make models of seafloor spreading, volcanoes, or hydrothermal vents or all three of these at different divergent boundaries. They should research where each occurs on Earth and label their models with the names of actual places. Give students an opportunity to explain their models to the class and to put them on display for others in the school to see.