Earthquake Waves. Purpose: To give students a visual example, using a slinky, of how an energy wave propagates through the Earth.

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1 Earthquake Waves Grades 4 & 5 Standards: Follows California Earth Science Standards for grades 4 & 5 Purpose: To give students a visual example, using a slinky, of how an energy wave propagates through the Earth. Questions for Students: What does a wave look like? Can a wave travel in more than two dimensions? Can a wave travel through metal, plastic, or wood? Materials Needed: 2 Student Helpers Space to stretch a slinky 5 and propagate waves Slinky Stopwatch Procedure 1. Stretch out the slinky on the bench top (or in the air) and ask a pupil to hold the other end. 2. Take a few coils of the slinky in your hand and suddenly let them go. Have a student start the stopwatch and time the wave until the wave bounces back and returns. Record on attached worksheet. Repeat 3 times. This produces a push-pull motion in the coils of the spring and a wave can be seen travelling. (The wave will also reflect back and forth a few times). This is a longitudinal wave, known to seismologists as a P-wave (primary wave). It can also be visualized as a push-pull, or compression, wave. 3. Let the wave dissipate out of the slinky. 4. Now give the spring a sharp sideways shake. Have a student start the stopwatch and time the wave until the waves bounce back. Record and repeat 3 times. This produces a transverse wave, which will reach the far end and reflect back and forth as before. Such waves are always slower than the P waves and are known as S- waves (Secondary waves). They are also known as shear waves. Observations: In the longitudinal wave the spring coils should look like a group traveling together through the length of the slinky. If this effect is not produced, try this portion of the experiment on a table. For the transverse wave, the slinky should have a wave shape traveling through the slinky. You do not need to shake the slinky to keep the wave shape forming; there should be only one wave traveling back and forth between you and the student.

2 Teacher Resource Background When an earthquake occurs, rock materials fail suddenly and the energy released travels in transverse and longitudinal waves. The first waves to propagate outwards are the P-waves (or primary waves). These waves travel faster due to their longitudinal form. The second wave set to propagate outwards is the S-waves (or secondary waves). The S-waves travel more slowly than the P-waves. This slinky demonstration was created to help students visualize the different patterns of these two wave forms. Learning Objectives: Students should be able to create a picture of how a wave propagates. Students will have a demonstration of the effect of earthquake wave propagation on the surrounding soil/rock materials. The students should also understand that although the slinky can move upwards or downwards or side to side, the final location of the slinky doesn t change after the wave has passed. Vocabulary: Longitudinal wave: a wave in which the direction of displacement is the same as the direction of propagation, as a sound wave. Transverse wave: a wave in which the direction of displacement is perpendicular to the direction of propagation. Pre-Activity Ask the students to share what they think of when they hear the word wave. How are waves related to energy released in an earthquake? Relate sound waves to energy waves and energy waves to the wave types propagated during an earthquake. Extra Resources Slinky Experiment: Video of waves:

3 Experiment Results: The students should be able to see the pattern illustrated below. Wave form (a) is P wave (Primary wave) and wave form (b) is the S wave (secondary wave). California Educational Standards, Grade 4 &5: GRADE 4: Standard Set 5: Earth Sciences (waves, wind, water, ice) 5. As a basis for understanding this concept: a. Students know some changes in the earth are due to slow processes such as erosion and some changes are due to rapid processes such as landslides, volcanic eruption and earthquakes breaks in the Earth s crust, called faults, experience slow movement called creep, and rapid movement that cause earthquakes. Standard Set 6: Investigation and Experimentation 6. Scientific progress is made by asking meaningful questions and conducting careful investigations. Students will: a. Differentiate observation from inference and how scientists explanations come from both observation and interpretation c. formulate and justify predictions based on cause-and-effect relationships e. construct and interpret graphs from measurements f. follow a set of written instructions for a scientific investigation. GRADE 5: Standard set 3: Earth Sciences (Earth s water)

4 NAME: DATE: Slinky Wave Experiment Pre-Lab: Question #1: What kind of waves do you experience in your everyday life? Question #2: Which of the following are types of waves that are the result of an earthquake? Experiment Observations: a. P-waves b. V-waves c. S-waves d. E-waves Question #1: What did the two types of waves demonstrated from this lab look like? Time Observations: Primary waves Secondary waves Average time Average time: Question #2: Which wave traveled faster? Does this follow what earthquake scientists have explained about the arrival times of the waves?

5 Slinky Wave Experiment ANSWERS NAME: DATE: Pre-Lab: Question #1: What kind of waves do you experience in your everyday life? Question #2: Which of the following are types of waves that are the result of an earthquake? Experiment Observations: a. P-waves b. V-waves c. S-waves d. E-waves Question #1: What did the two types of waves demonstrated from this lab look like? Label them. Primary Wave Secondary Wave Time Observations: Primary waves Secondary waves Average time Average time: Question #2: Which wave travelled faster? Does this follow what earthquake scientists have explained about the arrival times of the waves? The Primary wave traveled faster. YES. This follows the explained arrival time of waves.