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Discover a changing climate in an ice core

By Mike, 4 July 2013 Activity

Do you wonder why scientists are down in the Antarctic? One reason is to take ice cores, which keep a record of how the Earth’s climate has changed. To learn more (and make a tasty snack) try this totally cool activity!

Cocoa, lemonade, orange juice, food colouring and plastic cups.

You will need these materials.

food safety hazard iconSafety: When dealing with food, use clean hands and clean equipment.

You will need

  • Water
  • Freezer
  • Plastic cups
  • Lemonade (the fizzy, carbonated kind)
  • Food colouring
  • Fruit juice
  • Cocoa
  • Small mixing bowl
Plastic cup with a frozen layer on the bottom and a liquid layer on top.

Make your ice core by freezing it in different layers.

What to do

  1. Mix the components of each layer together following the instructions below, and pour the mixture into each plastic cup, filling up a third of each cup every time.
  2. Make and freeze each layer before adding the next, starting with layer one.
  3. When all three layers are frozen, you can eat it!

Layer one — A volcano has erupted and there is ash in the atmosphere. There is also pollen from flowering plants.

  • A cup of fruit juice. The pulp in the fruit juice represents pollen from plants found in the atmosphere.
  • A teaspoon of cocoa. This represents the ash and dirt in the atmosphere from a recent volcanic eruption.
Plastic cup with three differently coloured, frozen layers.

At the end you will have three different layers in your ice core.

Layer two — There is pollen in the atmosphere and carbon dioxide levels are increasing.

  • A cup half filled with fruit juice and half filled with lemonade. The bubbles in the lemonade are bubbles of carbon dioxide gas that represent carbon dioxide gas in the atmosphere.

Layer three — There is a dramatic increase in human-made carbon dioxide and a volcanic eruption.

  • A cup of lemonade. The bubbles of carbon dioxide in the lemonade represent the increased levels of carbon dioxide in the atmosphere.
  • A drop of red food colouring. The Earth is warming.

What’s happening?

Earth’s climate changes over time. The amounts of different gases, ash, dust and pollen in the atmosphere changes, as does the temperature of Earth.

Plastic cup with three different layers. The contents are overflowing.

Make sure you don’t fill the cup up too much!

In snowy areas, such as the Arctic and Antarctic, or on glaciers, snowfall freezes each year leaving a layer of ice as a record of that year’s snowfall. The frozen water in this ice record can tell us the approximate temperature of the Earth when the snow fell. Bubbles of air can also be trapped in the ice when it is frozen. When analysed, these small pockets of ancient air can tell us which gases and how much dust and dirt were in the air up to 800 000 years ago!

Ice cores are tubes drilled out from the ice, and can be up to three kilometres long. The ice cores are taken back to the laboratory so researchers can discover the information trapped inside.


Significant volcano eruptions in the past can be found and measured in ice cores. An erupting volcano will increase the amount of chemicals – such as sulfate – in the falling rain, snow and sleet (precipitation). This increase in sulfate can then be detected in the ice.

Researchers in Antarctica have found evidence for a large eruption that they think occurred in the year 1459 in an ice core taken from a place called Dome Summit South. Around 64 cm of snow falls at this site each year. You can find ice here that fell from the skies more than 80 000 years ago.

Ice cores can also tell us about out changing climate. Researchers have found that over the last 200 years the gas composition in the atmosphere has changed. The amount of carbon dioxide has risen by 45%, methane has risen by nearly 250% and nitrous oxide has risen by 18%.

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