Earthquake Shake Table

Students design and build model “buildings” from toothpicks and mini marshmallows, then test them on a pan of Jell-O/jelly that simulates shaking ground. By iterating their designs, they discover features (for example, cross-bracing, wide bases, tapered shapes) that improve earthquake performance.

1. Prepare the “shake table” by setting Jell-O in shallow baking pans the day before; keep covered so it stays springy.
2. Explain the design challenge and constraints: structures must be ≥2 toothpick levels high and include at least one triangle and one square.
3. Have students sketch ideas (label triangles, squares, footprint size, height) and then build prototypes using 30 toothpicks and 30 mini marshmallows.
4. Demonstrate a standard test: mark the table so every pan is shaken the same distance and for the same time using a steady back-and-forth shear motion.
5. Test one model at a time on the Jell-O; observe stability, tilting, and failures. Make a quick “after” sketch.
6. Discuss what worked (for example, cross-bracing, lower center of mass, wide base) and what failed (for example, tall slender towers without bracing).
7. Redesign and rebuild a second prototype that addresses weaknesses (add X-bracing, widen base, taper upper stories, tie levels together).
8. Retest using the same shaking protocol; compare first vs. second results and record conclusions.

Earthquake in the Classroom - TeachEngineering:

📄 Testing Model Structures: Jell-O Earthquake in the Classroom - ncwit.org - AUTHOR: https://www.teachengineering.org/activities/view/cub_natdis_lesson03_activity1

📄 Earthquake IN THE CLASSROOM - Cairns Regional Council: https://www.cairns.qld.gov.au/__data/assets/pdf_file/0011/469271/Earthquake-in-the-classroom-experiment.pdf

• Add “base isolation” by placing the structure on a stiff card resting on a few marbles/coins to model sliding supports.
• Change one variable at a time: height, footprint size, amount/location of bracing, or number of stories.
• Investigate “soft story” effects by making the first level taller/less braced and comparing performance.
• Explore resonance by shaking at different speeds and noting which frequency most strongly excites the structure.

• Do not eat the marshmallows or Jell-O used for testing; keep food items separate if offering a snack later.
• Wash hands before and after building; clean surfaces that contact Jell-O.
• Keep spills wiped up to avoid slips; cover pans when not in use to prevent drying and contamination.
• Use toothpicks carefully to avoid punctures; dispose of broken toothpicks promptly.

• Which design features helped most? (Cross-bracing/triangles, wide “footprint,” tied-together levels, and lower center of mass.)
• Why do triangles help? (They prevent shape distortion by resisting shear, adding lateral stiffness.)
• How does Jell-O represent real ground? (It models flexible, moving soil layers that transmit seismic waves.)
• How did you keep the test fair? (Same shaking distance, speed, and duration for every trial.)
• Why might a tall, narrow model fail more easily? (Higher center of mass and greater bending moments increase overturning and sway.)
• What does base isolation change? (It reduces motion transmitted into the building by allowing controlled sliding under the structure.)