Plate Tectonic - Earthquakes (K) Post Lab
 OBJECTIVES: Dramatizing the different types of earthquake intensities. Simulating the shaking during an earthquake. VOCABULARY: earthquake moderate stress strong volcano weak MATERIALS: none Students learn the shake, quake game. Pt. Reyes, 1906
 BACKGROUND: According to plate tectonic theory, the Earth's crust is fractured into a number of large tectonic plates, composed of the crust and upper mantle. The plates have moved very slowly, sliding over the the Earth's asthenosphere (a partially molten layer in the mantle). This movement causes a great amount of stress as the plates either bump together, moves away from, or slide past each other. The stress from plate motion builds up in rocks until they break. On the surface of the Earth, the break appears as a fault or fracture, such as the 1906 rupture in the picture above. When the break happens, the stress is released as seismic waves, which travel through the Earth. The larger the break, the greater the release of energy. In this Post Lab, the students will play the "Quake, Shake Game," which is a large motor skill activity. PROCEDURE: Review that earthquakes occur when the outer portion of the Earth's crust, is under stress. Slow movement inside the Earth and from rotating on its axis, all add stress. Emphasize slow by saying, "much slower than a turtle walking or the last drop of ketchup from a bottle." The movement of the Earth's crust is many times slower; it is actually about the speed at which fingernails grow. To relieve this surface stress, the Earth experiences volcanoes and/or earthquakes.    Explain that this slow movement will eventually cause breaks in the crust: earthquakes. When an earthquake occurs, it releases energy in the form of waves. It is this wave energy that we feel.    Explain the rules of the "Quake, Shake Game," to the class. In this game the students will pretend to be earthquakes and will dramatize the energy released by various earthquakes using their body movements.     A weak earthquake consists of slight body movement, a moderate earthquake consists of a little more violent motion than that of a weak earthquake, and a strong earthquake consists of shaking, rocking, and rolling.    Instruct one student be the shake master (similar to "Simon Says.")    The shake master announces one of the following:        "The surface of the Earth is under a little stress; I am a weak earthquake."     "The earth is under some stress; I am a moderate earthquake."     "The earth is under a lot of stress; I am a strong earthquake."    The rest of the class does the appropriate type of shaking. The teacher acts as the "judge" to observe if the students acted out the right kind of earthquake.    Change the "Shake Master" as needed.