Education »  Teacher's Toolbox »  Ice Cores (Secondary)

Ice Core Investigation

(Adapted from ASE Resources – Is there Life?’ http://www.sycd.co.uk/is_there_life/secrets_of_the_ice/activity.htm#resource)

Background:

This activity allows students to experience what kind of scientific work is being carried out at present by scientists working in Antarctica. Students play the role of an actual Antarctic scientist by analysing a section of an ice core.

Students analyse an ice core sample using a variety of scientific methods (see worksheet).

Assessment:

Students produce a formal written report on the experiment with an emphasis on the analysis of their results.

Activity:

Student Worksheet

How do scientists know what the Earths climate was like thousands of years ago?

They take ice cores from undisturbed places, such as Antarctica, and analyse what’s in the ice so that they can tell what the environment must have been like when the ice formed.

September, 2003 – Antarctica

A research team has been drilling ice core at Vostok, Antarctica. The core is 2 200 metres long and could date back as far as 500 000 years is shipped from Antarctica. The ice core is so long that it has been split into sections and sent to various research laboratories for testing.

What secrets does the ice hold?

TASK:

1. Read briefing
2. Separate, measure, and then melt layers of ice.
3. Carry out tests on layers to see what they contain.
4. Compare the results and suggest what the layers indicate about the environment at the time they were formed.
5. Write a report for other research teams to compare their samples with.

BRIEFING:

When snow falls it settles and turns to ice, every year more ice forms on top. Ice cores therefore hold information about the environment at the time the snow fell. Each research group has been sent an ice core made up of 2 distinct layers to be analysed and compared, to establish what the environment was like during the particular time in the Earths history that the ice formed.

ICE CORE TESTS:

A. Separate the Ice Core Layers

Procedure

1. Place ice canister water bath with hot but not boiling water.
2. When the ice around the edge starts to melt, take the canister out of the water bath.
3. Carefully remove the ice from the canister using a dinner knife if necessary. (If the ice doesn’t come out easily, put it back in the water bath and try again).
4. Dry the ice and break apart the two layers.

B. Investigate Snowfall

The thickness/depth of the layers indicates how much snowfall there was in that period – this in turn is an indicator of climate change.

Procedure

1. Use a ruler to measure the depth of each layer. (You need to do this quickly so the ice doesn’t melt!)
2. Compare the depths and each layer and suggest what conclusion can be made from your results.

MELT THE ICE CORE LAYERS IN SEPARATE LABELLED BEAKERS FOR THE FOLLOWING INVESTIGATIONS:

C. Investigate Volcanic Eruptions

Volcanic eruptions release a lot of dust into the atmosphere which can travel over great distances before falling back to Earth. The amount of dust in a sample can be used as an indicator of major volcanic eruptions in the past.

Procedure

1. Decant 20cm³ of ice water from one layer into a smaller beaker.
2. Using a dust scale* place your beaker over one dot at a time and finding which dot you can just see through the water/beaker.
3. Repeat steps 1 and 2 for the second layer.
4. Compare the relative dust concentration for each layer and suggest what conclusion can be made from your results.

* Make your own dust scale by drawing 6 circles and shading them on a white sheet of paper, one end being black and the other white and the remaining circles shaded different to different shades of grey. Number your circles, and record which dot can just be seen through the sample, this way the samples can be compared.

 

D. Investigate Pollution

An indicator of pollution is the amount of heavy metals, such as copper, dissolved in rain water.

Procedure

1. Use the same beakers of water you used in part 3 and place over a white tile.
2. Add a small amount of dilute sodium hydroxide from another test-tube to each beaker.
3. If copper is present your sample will turn slightly blue in colour. You can compare your sample to the original if you’re not sure whether there has been a colour change or not.
4. Compare the relative copper concentration for each layer and suggest what conclusion can be made from your results.

E. Investigate CO₂ Levels

CO₂ levels in ice layers are an indicator of air temperature at the time the ice was deposited.

Procedure

1. Put 5cm³ of each sample in separate test-tubes. Add a few drops of phenolphthalein indicator solution. This solution will stay clear in acid and go pink in alkali solution (CO₂ makes water acidic so your solution should stay clear).
2. Sodium hydroxide will neutralise the solution. Record the amount of sodium hydroxide in the burette. Add sodium hydroxide slowly from the burette to a sample placed on a white surface. As soon as the sample turns pink stop adding sodium hydroxide.
3. Record how much sodium hydroxide is left in the burette, and calculate how much was needed to neutralise the sample.
4. Repeat this process for your second sample.
5. Compare the relative CO₂ concentration for each layer and suggest what conclusion can be made from your results.

F. Investigate Plant Life

The presence of plant life is indicator of milder climates.

Procedure

1. Using a pipette put a drop of sample onto a microscope slide.
2. Observe through a microscope and look for any evidence of plant life in the sample.
3. Repeat this process for your second sample.
4. Compare your observations for each layer and suggest what conclusion can be made from your results.

TECHNICIANS NOTES:

Making Your Ice Cores

Requirements (for the class as a whole)

Ice core

The ice core is a piece of plastic tubing (approximately 20cm long with a diameter of 4-5cm is fine) with end caps holding two layers of frozen water. The layers have been doctored so they have different properties.

1st Layer (quantities per litre)

• 500 ml carbonated sparkling water plus 500 ml tap water, to put lots of CO₂ into solution.
• Stir in gently 5g of china clay or powder paint or ground up cat litter, to make the solution look dusty for Part C. Let it settle.
• Decant liquid to remove sediment at bottom
• Add 50ml of 0.1M copper chloride solution, to put lots of heavy metal ions into solution.

2nd Layer (quantities per litre)

• 100 ml carbonated sparkling water plus 900ml tap water to put a little CO₂ into solution.
• Stir in gently 2g per litre of china clay or powder paint or ground up cat litter, to make the solution a little bit dusty for Part C.
• Let it settle. Decant liquid to remove sediment at bottom
• Add 10ml of 0.1M copper chloride solution, to put a few heavy metal ions into solution.
• Add enough Chlorella for pupils to be able to see evidence of plant life. (Alternatively you could try ground grass or leaves). The amount needed varies depending on your Chlorella stock.

NB The quantities of chemicals are not critical. They are designed to give easily observable differences between the layers.

Depending on the size of your cores pour in enough of ‘layer 2’ to fill 2/3 of the container (around 200ml) and then freeze it.

Put a circular piece of tissue paper on top (this makes it easier to separate the layers), then carefully fill the rest of the container (around 130ml) with ‘layer one’ (remember to leave a small gap at the top as the water will expand when frozen). Finally, re-freeze.

Requirements per group

Part A

• 1 ice core in container
• Access to hot water bath or tub containing water from a kettle
• Dinner knife
• Paper towels

Part B

• Ruler

To melt the ice cores:

• Access to hot water bath
• 2 x 250ml beaker

Part C

• Small beaker
• 1 piece white paper
• Pencil

Part D

• Small beaker
• 1 white tile
• Sodium hydroxide solution (0.4M – 1.0M, depending on your own risk assessment)

Part E

• Small beaker
• Phenolphthalein indicator solution and pipette
• Fresh, dilute sodium hydroxide solution (0.1M) in a burette or supplied with a graduated pipette so pupils can measure start/end volumes

Part F

• Optical microscope
• Two slides

Safety

1M sodium hydroxide is corrosive and dangerous to eyes and skin.

Eye protection must be worn at all times.

Warn students that the solutions of sodium hydroxide are corrosive and dangerous to eyes and skin. Make sure that eye wash facilities are available.

Acknowledgement:

ASE Resources – Is there Life?’ http://www.sycd.co.uk/is_there_life/secrets_of_the_ice/activity.htm#resource