Lesson 4: Earthquakes and Moving Plates

Activities

Activity 1: Make an Earthquake

Materials: 18-24 sugar cubes, 3 pieces of cardboard, clay (kit), newspaper, sand (kit), soil (kit)
Many factors influence how much damage an earthquake does to a building. Two important factors are the strength of the earthquake and how far the building is from the earthquake's epicenter. Other factors can include the ground the building is on, the materials used to construct the building, and the building's shape or design.

In today's demonstration, you will explore how a building's shape and the ground the building is constructed on affect its ability to withstand an earthquake. When you create your buildings, use the same number of sugar cubes each time but vary the shape of the building. One version may be very tall, one may be in a pyramid shape, and another may be a square or rectangle. Follow these steps:
  1. Cover the floor with newspaper or do the demonstration outdoors.
  2. Place one or more cardboard sheets on a table with 2 inches of cardboard hanging off the end.
  3. Put down three separate mounds (about 1" high) on which to build your buildings -- use soil, clay, and sand either from near your house or from the science kit. Note: If you use the clay, sand, and soil from the science kit, use just the amount needed and try to keep the mounds separate so that you can sweep the materials back into the bags afterward. You will use the clay, sand, and soil in future lessons.
  4. Place 3 buildings made of 6-8 sugar cubes each on top of each mound. Make each building the same size and shape.
  5. Tap the bottom of the cardboard. Keep tapping until one or more of the buildings loses some sugar cubes.
  6. Repeat Steps 4 and 5 with a different building shape.
Share your observations with a parent. Which type of "ground" provided the most stability? Which building shape was sturdiest? Did the buildings' distance from the "epicenter" (the place you were tapping) make a difference?
Your child will do a demonstration to test the effects of an earthquake. This is a messy activity and should be done outside, in an area easy to sweep, or over newspaper that can be thrown out afterwards. Note that your child can collect sand, clay, and soil from near your house or can use the materials provided in the science kit. If she is using the science kit materials, remind her to use only part of each bag, and help her keep the 3 mounds separate from one another. After the activity she should sweep each material back into its bag for use in future lessons. (It's ok if a little of one material mixes with another, but they should be kept mostly separate.)

Ask your child to share her observations with you. Also ask her what factors architects and engineers might consider when designing or constructing buildings in areas that tend to experience strong earthquakes.

Activity 2: Making Some Waves

Materials: Dirtmeister's Nitty Gritty Planet Earth by Steve Tomecek, 10' piece of rope*, Slinky or Slinky Jr. (kit)
When an earthquake occurs, a huge amount of energy is released. This energy moves outward from the fault in the form of vibrations or waves. As these strong waves move through the earth, the ground shakes. For this activity, you will create some waves similar to the ones produced by an earthquake.

If you have a long piece of rope (about 10 feet long), try the demonstration found at the bottom of p. 36 in the book. Afterward, follow these steps:
  1. Firmly tie one end of the Slinky to the doorknob of a closed door. (If a parent or friend is available to help, that person can hold one end for you. Your helper should keep his or her end of the Slinky firm and steady throughout the demonstration.)
  2. While you hold one end of the Slinky, walk away from the door (or helper) so the Slinky isn't slagging in the middle. Do not stretch it all the way out.
  3. To make a P wave, quickly push and pull your end of the Slinky toward and then away from the door/helper. Don't let go of your end! Watch as the wave travels down the Slinky. The wave may even bounce at the other end and head back toward you.
  4. To make an S wave, jerk your end of the Slinky quickly side to side once. Again, don't let go. The wave should once again travel down the Slinky. Notice how this wave is different from the P wave.
  5. If you're having trouble seeing the waves, repeat Steps 3 and 4 at different distances from the door/helper and with different forces of pushing/pulling and jerking side to side. You can also try the demonstration on a table or on a bare floor with your helper again holding one end firm and steady.
Your child used a Slinky to help her better understand the two main types of energy waves (called seismic waves) that occur during an earthquake. If a long rope was available, your child also followed the directions in the book to create waves. Ask your child to explain the differences she saw between the two wave types. She should have noticed that the P wave (push/pull motion) moved the Slinky in the same direction the wave was traveling, but the S wave (side to side motion) moved the Slinky in a different direction than the wave was traveling. If she also did the rope demonstration, ask her how the waves she produced with the rope were similar to or different from the ones in the Slinky demonstration.

Activity 3: Nearby Fault Lines?

Materials: colored pencils
Find the "Earthquake Shaking Hazards in the United States" page. First, use colored pencils to color each patterned box of the key. Next, find your state on the map. Follow your key and color in the pattern in your state as well as all adjacent states. (Adjacent states are ones surrounding yours. Some states may have only a few adjacent states while others may have several. Alaska and Hawaii have no adjacent states.) What is the earthquake hazard level for your state? What about nearby states? Are you surprised by the earthquake risk in your area? Share this information with a parent.
In this activity, your child will investigate earthquake hazard areas and determine the earthquake hazard level in your state and surrounding ones. If your area has a history of earthquakes, share this information with your child.