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Liquefaction Tank

Falling over isn’t the only risk from an earthquake. What happens when you mix earth and water?

Australian Curriculum links

  • Science > Earth and space sciences > Year 6 > ACSSU096

You’ll need

  • A large, clear plastic tub
  • Water
  • Sand or soil
  • Wooden blocks and/or toy cars and figures
  • A mallet OR a skateboard or trolley on wheels

Try this

  1. Fill the tub with soil so it is at least 8 cm deep
  2. Pour water over the soil, so that the water level is about half of the soil level.
  3. Smooth and pat down the soil surface. Add more dry soil if the top soil is starting to get wet.
  4. Place wooden blocks, toys and figures on the surface of the soil
  5. Place the tub on a trolley or skateboard and rock strongly from side to side for about 30 seconds, or until the water seeps through the surface. If you do not have a trolley or skateboard, hit the side of the tub with a mallet until the water seeps through the surface.

Further investigation

  • What happens if you compress the soil more firmly before you shake it?
  • What happens if you mix the soil or sand into an even mixture with the water before you shake it?
  • Try different types of soil and sand mixtures. Are some of these less likely to liquefy?
  • What happens if you do not add water before shaking?
  • Try using cornflour and other materials.

What’s happening?

Liquefaction occurs when wet soils are compressed due to earthquakes or other natural processes. The water is forced out of the soil due to the high pressure from the earthquake as the grains of soil are pushed together. This causes soil and sand to flow as water.

Real world links

Liquefaction is a real risk in some low-lying, earthquake-prone areas. It mostly occurs in relatively new soils, such as estuaries and flood plains, which are also relatively wet. In the Christchurch earthquake of 2011, liquefaction occurred in many areas. People reported that sand bubbled up out of the ground, which left buildings and cars submerged in mud once the earthquake subsided. It also made the streets very covered in mud and difficult to clean up.