Plate Tectonic - Hazards (K) Pre Lab
 OBJECTIVES: Learning to think critically during an earthquake. Exploring the sounds of an earthquake. VOCABULARY: bang crash earthquake rumble MATERIALS: worksheet crayons Students compare the sounds of an earthquake. Damage in San Fernando, California, 1971
 BACKGROUND: The first sign of an earthquake is often a sharp thud, signaling the arrival of compressional seismic waves (P wave). The second sound and sensation are a rumbling caused by ground rolling from surface waves. A geologist in the Valdez, Alaska, 1964 earthquake described the motion as follows: "The first tremors were hard enough to stop a moving person and shock waves were immediately noticeable on the surface of the ground. These shock waves continued with a rather long frequency which gave the observer an impression of a rolling feeling rather than abrupt hard jolts. After about 1 minute the amplitude or strength of the shock waves increased in intensity and failures in buildings as well as frozen ground surface began to occur..." The severity of an earthquake can be expressed in several ways. The magnitude of an earthquake, or the amount of energy released can be expressed by the Richter scale. The Modified Mercalli Scale expresses the intensity of an earthquake's effects in a given locality, as experienced by people. PROCEDURE: This coloring and word exercise serves as a springboard to begin a discussion with your students about the sounds caused by an earthquake. Discuss that there are natural sounds from an earthquake, like "rumble," but there are also other sounds like "bang" and "crash" that indicate that something is falling or breaking.    Ask the students which sounds should serve as a warning if an earthquake should occur. This exercise emphasizes to the students how to evaluate the situation during the earthquake, using all their senses. For example, by listening to the noise the earthquake makes and observing shaking objects, they would be able to determine whether an earthquake is a weak, moderate, or strong event. This will make them better prepared to take action.    Instruct the students to color the worksheet, and to think about sounds made by earthquakes. You may also want students to simulate the sound of an earthquake "rumble" by having them all softly make a rumble sound. Practice as a whole group and then have students do a "rumble wave" (like the waves made by a crowd at a football game, where the sound gets progressively louder and then softer). This would simulates the movement of the "energy wave."