Human Wave: Modeling Seismic Waves in the Classroom

How can we model seismic waves in the classroom?

How can I get across the idea in a classroom activity using no props?
Given the motion behavior for the human wave, can you guess which wave, P or S will be faster?Can I model a liquid core using this method?

Roger Groom* has his class model P and S seismic waves through solids and liquids.

This is a DRAFT version to be updated. Caveats include:  The arms-over-shoulders method is a far better analogy to hand-holding method for best physics as noted in subtitles in the video. With hand holding, energy propagates down the line due to internal energy from the particles (the brain telling the other arm to raise)  rather than transferring from one particle to the next as in the arms-over-shoulders method that happens automatically.

NOTES FOR TEACHING:

This demo is a simplified model of natural phenomena. As such it is especially important to emphasize both the strengths and weaknesses of the model to students. Such an explicit discussion helps students focus on the model as a conceptual representations rather than a concrete copy of reality. See Key points below.

*Mount Tabor Middle School, Portland OR


Keypoints:

Points to address with students:

  • The model has  scale and compositional limitations
  • Seismic waves only travel outward all directions; not just in one direction like the line of students
  • Seismic waves also travel at speeds that are much faster, about 3000x faster, than the waves in the Human Wave model
  • The particle motion of an S wave can be in any direction that is perpendicular to the direction of wave propagation; not just up and down as shown in the demo
  • Even though kinetic theory is not the targeted learning outcome of this demonstration, instructors should be specific about pointing out that in this demo the student “particles” are stationary for the purposes of the demo, but actual particles are constantly in motion, even in a solid


Level: Novice

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