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Volcano's Deadly Warning
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Viewing Ideas
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Before Watching
Ask students to compare and contrast volcanoes and earthquakes. What causes a volcano to erupt? (Magma flowing from Earth's interior). What causes an earthquake to happen? (Continental plate movements cause most earthquakes.) What is similar about both? (They both involve seismic waves, can cause major destruction, and can be difficult to predict). Waves are a way of transmitting energy. While energy is transferred by a wave, the matter through which the wave moves does not travel with the wave. This can be demonstrated by shaking a piece of string up and down. (See illustration.) Explain to students that the volcanic seismic waves discussed in this program represent one way that energy is transmitted from Earth's interior to its surface.
The string moves up and down while the energy is transferred along its length.
Scientists must decide when to evacuate towns near a volcano that appears to be about to blow. If people are evacuated and the volcano does not erupt, they are less likely to trust the next evacuation request. Have students consider what they would do if they were asked to evacuate for an indefinite period. How would they decide whether to go? What would they bring?
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