Lesson: Balancing Act

Watch a video about earthquakes and discuss their effects.

• Show the video “Inside Earthquakes.” Ask: What kinds of things are most likely to topple during an earthquake? (Things that are not well-balanced or not secure, etc.) Show students photos of balancing boulders from the article. Ask: What might happen if a strong earthquake were to occur near these rocks? (They could fall over.)

Conduct a simple demonstration of shaking and toppling.

• Tell students they are going to model how earthquakes can cause structures or objects to topple. Give each student two quarter sheets of paper and a book (or a flat item that slides easily) to mimic an earthquake. Show students how to fold one sheet “hotdog style” (folding across the short edge) and the other “hamburger style” (folding across the long edge). 
• Have students stand the sheets up on top of the book, with the folds vertical and facing the same direction. Ask: What will happen if you push and pull the book with more force over time to show stronger earthquakes? Have them test their predictions and discuss what happened. (Most likely, the taller one will topple before the shorter one.) Demonstrate how to increase the strength of the “earthquake” by sliding the book more quickly back and forth.

Read the article and describe key information. 

• Preview the article. Read the main story aloud, then the sidebar “How Balanced Rocks Can Form.” Have students closely compare the illustrations for steps 2 and 3. Ask: What does weathering from wind and water have in common with an earthquake? (They both can change the boulders.) How are they different? (Weathering is much slower.) 
• Have students reset their papers and materials used in Step 2. Ask students: Imagine these pieces of paper are rocks. They are balancing and standing right now. Has there been an earthquake strong enough to knock them down? Tell students to shake them gently and then stop. Ask: Was that “earthquake” strong enough to knock the rocks down? Repeat the shaking with more intensity. Then discuss how this earthquake and these rocks connect to conclusions scientists drew about the strength of earthquakes that had already occurred in an area.  
• Have students complete the No-Sweat Bubble Test in pairs and discuss answers as a class.

Experiment with the concept of balance and center of mass using index cards and pencils.

• Preview the Find Your Balance skills sheet. Complete steps 1-6 as a class. Then give students additional index cards for steps 7-8 and have them discuss ideas with a partner. Let students share how they balanced their index card. 

Analyze an investigation, focusing on the data collected and the conclusions scientists drew.

• Preview the “Investigate It!” questions on the skills sheet. Allow students to work together before discussing as a class.

⇨ Learning Extension: Have you ever experienced an earthquake? Write a short story about the experience. Or, try to imagine what one of those earthquakes would be like. What would you see, hear, and feel? How would you react?