Targeted Age: Elementary to High School Activity Structure: Group Activity (2 to 3 students) Indiana Standards and Objectives: 6.3.22, 7.3.4, and ES 6.3 Materials:
- Container, at least 8 cm (3in) deep
- 1 to 2 large spoons
- 1 to 2 ping pong balls
- Building replica or wooden block
- Clean, well-sorted sand
This activity allows students to construct a small-scale model of liquefaction, a hazard associated with strong-magnitude earthquakes. The sand, water, and ping pong ball(s) represent the composites of soil: sediment, water, and air, respectively. The shaking, representative of seismic waves, will be generated by the students.
Liquefaction is a physical process that causes soils to temporarily lose strength and behave more like a viscous fluid than a solid. Once liquefaction has occurred, the soil is no longer able to support the foundations of structures such as buildings and bridges.
High-energy seismic waves that pass through saturated, silty, or sandy soils can increase the pore water pressure and allow air contained in the sediment to escape. This increase can exceed the strength of the soil column, causing liquefaction. The change in pressure allows soil particles to easily move with respect to each other. Dynamite blasts can trigger a similar effect on a much smaller scale.
Liquefaction is typically limited to relatively loose, silty or sandy soil deposits where groundwater is within 9 meters (30 feet) of the surface.
- Have the students fill a container with playground sand to a depth of at least 6cm (2.5 in).
- Add enough water to moisten the sand grains completely but not so much to cause standing water to build up on the surface of the sand. Use a large spoon to periodically mix water and sand.
- Once all the sand grains are moistened, bury the ping pong ball(s). Make sure the ball is completely covered with sand.
- Gently smooth out the surface of the sand and place the replica of a building on the surface of the sand somewhere near the center (fig. 1).
- Now gently shake the container to simulate an earthquake. This may take a few seconds. Students should continue to shake the container until water begins to appear on the surface and the ping pong ball emerges (fig. 2).
- Ask students to describe what they observed during the shaking.
- To repeat the activity simply remix the water and sand until the surface water is no longer visible.
- What does the sand and water represent in this model? What naturally occurring event does the shaking represent?
- What causes the water and the ping pong ball(s) to rise to the surface?
- What happened to the building once liquefaction was visible? Does this accurately reflect the response of structures during liquefaction?
- After the earthquake shaking stopped, describe the appearance of the surface? Look at the surface again after 30 minutes. Explain any changes that have been observed.
Extension or Enrichment Suggestions:
Ask students to use Indiana Geological Survey Miscellaneous Map 81 or 86 to determine the liquefaction potential of the surface materials in their local community. There are data also available on IndianaMap (http://maps.indiana.edu/) as a GIS layer.
Redesign the activity so that each group uses a soil of a different composition. Have students report their observations to the class and then ask the students to determine which soils are more prone to liquefaction.
The Indiana Geological Survey has additional educational resources that support the teaching of earthquakes and liquefaction:
- The Quake Cottage Program (http://igs.indiana.edu/EarthquakeExperience/)
- Online Web Articles (http://igs.indiana.edu/Earthquakes/)
- Miscellaneous Map 81 (scale,1:193,061) and 86 ( scale, 1:500,000): Map of Indiana Showing Liquefaction Potential of Surficial Materials (2011)
- Miscellaneous Map 84 (scale, 1:193,061) and 85 (scale, 1:500,000): Map of Known Faults and Historic Earthquake Epicenters Having Magnitude 3.0 and Larger in Indiana (2012)
- Preparing for Indiana’s Earthquake Risks (MI53)