Demonstrating P and S Waves with a Slinky

Pier Bartow, Klamath Community College.

This page is a supplement to the original activity description found here

Short description of the activity:

P and S seismic waves can be demonstrated with a slinky. P waves have energy traveling parallel to the direction the wave is moving. S waves have energy traveling perpendicular to the direction the wave is moving.

How does this activity lend itself to teaching the methods of geoscience?

The students can see that I am putting energy into the slinky in two different ways. A quick push down the length of the stretched out slinky demonstrates a pressure wave and a quick flip of the wrist will send a shear wave down the slinky. This allows the students to answer questions about why P waves travel faster than S waves. Also, they can see why P waves can travel through a liquid while S waves cannot.

Specific Adaptations: How do these help the activity address the methods of geoscience?

I first do the demonstration as described above then they break up into groups to experiment for themselves. I provide one slinky for every 4 students. We then talk about the liquid outer core of the Earth and how this would effect seismograph readings around the globe. Then I give a quiz to help them focus on what they have learned.

Assessment: How are the methods of geoscience assessed?

A short quiz asks the students to explain the differences between P and S waves, and their unique attributes.