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Don't get foolED

By what floats

Photo of an iceberg nearby the shore with a dozen people looking at it

We often say that only the tip of the iceberg can be seen, which suggests that there is much more ice under the water level. But how much of the iceberg is in the water compared to what we see above water? And how does such a huge and heavy amount of ice float?

In this session, we will create our own icebergs and measure their equilibrium position. We'll be able to compare the results from our experiments with our home-made icebergs to the observations made using an iceberg simulator. Ice has very unique properties that allows it to float in water but a large amount of the iceberg can't be seen from the shore of Newfoundland or when on a boat at sea for example. This hidden underwater part of the iceberg could be a risk for navigators.


Part 1 - Make your icebergs

1. Material: balloon, plastic bag (ziplock type) and freezer

2. Fill in the balloon with water until it reaches the size of a big orange then tie it. Do the same with the plastic bag.

3. Put them both in the freezer for a few hours until they are frozen

Part 2 - Make your hypothesis

1. While you wait for your icebergs to freeze, draw different shapes of iceberg on the simulator bellow and observe how each iceberg floats

2. Write down your observations. It could for example include, the orientation of the iceberg (vertical? horizontal? it depends?) and how much of the iceberg is under and above the water (mostly above water? half-half? mostly underwater? it depends?)

3. Do you notice similarities in your observations when trying different shapes? Can you make an hypothesis (a guess you make based on information you already know) about how icebergs usually behave in the water?

Draw an ICEberg and see how it floats: 

  • Click in the blue section and draw a shape then release and your iceberg will appear.

  • How big are the sections of the iceberg above ABOVEand UNDERwater?

  • What is the orientation of the iceberg? 














Part 3 - Prepare for the live experiment

1. Material: Large transparent container (bowl, bucket, fish tank or else), ruler and calculator

2. Keep your iceberg in the freezer until we set the experiment together

Credits to Joshua Tauberer for the Iceberger simulation. Inspired by tweets by @GlacialMeg 


Megan Thompson-Munson is a PhD student in geology at the University of Colorado, USA. She is an expert in glaciology and studies ice sheets in Greenland.

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