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Biscuit Geology

A tasty way to crack geology!

Australian Curriculum links

  • Science > Earth and space sciences > Year 6 > ACSSU096
  • Science > Earth and space sciences > Year 9 > ACSSU180

You’ll need

  • Flat cream-filled biscuits such as Oreos

Try this

  1. Take a cream-filled biscuit and slide the top in one direction. What happens?
  2. Break the top layer of a cream-filled biscuit and separate the two halves. What happens?
  3. Break the top layer of a cream-filled biscuit and try to slide one half under the other. What happens?
  4. Break the top layer of a cream-filled biscuit and push one half up and the other half down while sliding against each other. What happens?

Further investigation

  • Can you think of a plate boundary that acts like each of these actions?
  • Which was the most difficult?
  • Which caused the most damage to the biscuits?

What’s happening?

The top layer of the biscuit represents the Earth’s crust or lithosphere, where we live. These also represent tectonic plates. The creamy layer represents the asthenosphere, which is soft and molten. The bottom layer of biscuit represents the lower mantle, which is hard. The plates slide over the mantle, just as the biscuit slides over the creamy layer. The biscuit halves sliding away from each other represents the divergent plate boundary. These occur in mid-ocean rifts, where the mantle emerges and cools forming new rocks. When we try to slide one biscuit under another, this represents a transform plate boundary.

Real life links

Marine fossils have been found on the summit of Mt Everest. About 50 million years ago, the Indian Plate began crashing under the Eurasian plate. As the Indian plate was forced underneath the larger Eurasian plate, it caused crumpling in the Earth’s crust and created the highest mountain range in the world. The Indian plate is still crashing into the Himalayas and they are still growing taller at 5 mm per year. However, there are many earthquakes in this region due to the colliding plates.