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Climate Change – Causes and Effects: How do we know how the climate changed during the Quarternary period?

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Minimum time required

25 minutes

Resources needed

Methodology & teacher’s notes

  1. Pose the following questions to students (write them on the board, provide them with a copy, use the optional worksheet etc…)
    1. How does ice made from snow that fell in the past give us readings of past climate?
    2. What is an ice core?
    3. How far back are scientists get climate records from ice?
    4. BONUS: What is meant by a ‘proxy’?
    5. BONUS: How do scientists get to the air trapped in the ice without contaminating it with today’s air?
  2. Students to cut out mystery cards (can be one set each, per pair or per group) students are to answer the above questions using the mystery cards – it is up to you how the students record their responses. Putting the mystery cards in the following logical order to tell a story is the easiest way to come up with ideas for answers:
  3. Earth’s Quaternary Period was a time of glaciation
  4. Even the ‘warm’ interglacial periods saw glaciers, snow and ice at Earth’s poles
  5. In glacial areas snow and ice are able to accumulate (build up)
  6. Snow traps air as it falls
  7. As it builds up, the layers of snow towards the bottom compresses to form ice
  8. The older the ice, the older the air trapped as bubbles inside
  9. The further you drill into ice, the older it is
  10. The oldest ice core column drilled so far is 2.7 million years old, taken from Antarctica
  11. Trapped bubbles give a reading of CO2 levels, and give temperatures by measuring isotopes of oxygen
  12. Readings from ice cores can be compared with other ‘proxy’ evidence left in tree rings, ocean sediments, coral reefs, and layers of sedimentary rocks

Referring to the list above:

Cards ‘d’, ‘e’ & ‘f’ help to answer question 1

Cards ‘g’ & ‘h’ help to define an ‘ice core’ (question 2) – a column of ice that is drilled, usually the longer the core the greater the time period it covers

Question 3 can be answered with card ‘h’, although it may be possible to go back further than this. Since you need ice to have accumulated even in warm periods, ice cores usually cover the Quaternary period (up to 2.6 million years ago).

Card ‘j’ gives a hint about what is meant by a ‘proxy’, which is an indirect measurement of something. For example, you can’t directly measure the temperature from thousands of years ago with thermometers for but tree rings can tell you how warm or wet a particular year was by how big they are (very simplified!)

No card helps with the answer to question 5, rather challenges students to think how it would be done. The standard way is cut a piece of ice, put it in a flask and pump out the air so the ice is in a vacuum. Then melt the ice so the flask contains the old air that can be analysed. Here is a segment of a really good video describing the process more fully, although students don’t need to know this level of detail.

Supplementary Activities from the #GeographyTeacher Community

Working very well in tandem with these activities, Ewan Vernon has created instructions using self-made mock ice cores based on a resource by Ohio State University. He has shared them freely via Internet Geography.

View the other lessons in this series:

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