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Liquefaction

In this activity, students explore how vibrations can make solid ground unstable.

Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading.  Liquefaction occurs when vibrations from seismic waves increase water pressure between soil grains, transforming once cohesive soil into a slurry of mud!

Liquefaction is more likely to occur in loose to moderately saturated granular soils with poor drainage, such as silty sands or sands and gravels. If the pressure of the water between soil grains is great enough, it will have the effect of holding the particles apart and of producing a condition that is practically equivalent to that of quicksand.

Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world. The building codes in many countries require engineers to consider the effects of soil liquefaction in the design of new buildings and infrastructure such as bridges, embankment dams and retaining structures

Objectives

  • Describe the effect of earthquakes on mud and sand

Materials

  • Per Demo or Group:
    metal cake pan
    sand
    water
    smooth brick
    rubber mallet
    ping pong ball or cork (optional)

Key Questions

  • What happens to the sand and brick?
  • Was this the same as your predictions?

What To Do

  1. Fill the pan with sand. The deeper the sand, the better.
  2. Put the pan on the table.
  3. Pour water into the pan so it reaches just below the surface of the sand.
  4. Wiggle the skinny end of the brick down into the wet sand so it stands up like a building would.
  5. Now very gently, repeatedly tap the side of the pan with a mallet.

Extensions

  • Submerge a buoyant object (ping pong ball) in the sand before starting the demo and watch the result on that object: Why is it able to float to the surface?

Other Resources

IRIS Earthquake Science | Amplification and Liquefaction | How will 3 buildings, engineered equally, on different bedrock, react to an earthquake?

Prepared BC | Earthquake and Tsunami Guide PDF

Government of British Columbia | Earthquake Preparedness and Response

Government of Canada | Natural Resources Canada |  Earthquakes Canada

U.S. Geological Survey | Earthquake Hazards Program | Earthquakes for Kids

Cybersleuth Kids | Earthquake Resources