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Glaciers Then and Now

Teri Eastburn, Lisa Gardiner, Windows to the Universe

In this activity, students compare two photographs (with time spans of 30-100 years between photos) of specific Alaskan glaciers to observe how glaciers have changed over the time interval. Activity is a good kickoff for learning about glaciology - how and why glaciers form, grow and shrink, and their relation to climate change.

Activity takes one to two class periods.

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Melting Ice and Permafrost
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Grade Level

Middle (6-8)
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A little simplistic for 8th grade but very suitable for grades 6-7.

Regional Focus

US Alaska
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Climate Literacy
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Climate change has consequences
About Teaching Climate Literacy
Other materials addressing Climate change has consequences

Excellence in Environmental Education Guidelines

2. Knowledge of Environmental Processes and Systems:2.1 The Earth as a Physical System:A) Processes that shape the Earth
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A) Processes that shape the Earth.

Notes From Our Reviewers The CLEAN collection is hand-picked and rigorously reviewed for scientific accuracy and classroom effectiveness. Read what our review team had to say about this resource below or learn more about how CLEAN reviews teaching materials
Teaching Tips | Science | Pedagogy | Technical Details

Teaching Tips

  • Students would be likely to learn more from the activity and be better able to respond to the discussion questions if they did their own investigation of the nature of glaciers worldwide, using the resources provided at the end of the activity.
  • Targeted to grades 4-8, but educators should adapt accordingly; older students will need to do more than compare photographs.

About the Science

  • The background information on glacier formation is minimal and needs to be supplemented by the educator.
  • Includes a very illustrative documented series of glacier images that provide a good general exposition of glacier change.
  • Activity looks at glaciers in Alaska, but discussion questions appear to apply to glaciers globally, making the assumption that what is happening in Alaska is happening everywhere - should be supported by some additional materials.
  • Comment from scientist: “Continental Glacier” is equated with “Ice Sheet” in the activity, which is not quite correct. “Continental Glacier” is an ambiguous term, and although it is used as a synonym for ice sheet (e.g. in the Wikipedia entry on glaciers), it also refers to a glacier of any size located in a continental environment (as opposed to a maritime environment). It's suggested educators drop this term. Another error: iceberg calving is not listed among the causes of glacier retreat. Most of the photo pairs shown here depict retreat due to calving.
  • Comment from scientist: The educator should introduce the concepts of accumulation (see paragraph 2) and ablation (or loss), and then present growth and decay (or advance and retreat) as the balance between these. The text only describes accumulation and retreat and doesn't emphasize that glaciers can exist in a steady state.
  • Comment from scientist: For advanced classes, the educator could also describe the distinction between retreat by climatically-controlled mass balance (i.e. accumulation vs. melt, primarily) and retreat by calving, which can be quite independent of climate forcing. This would be an arcane point far beyond the level of the activity, except for the fact that 5 of the 8 photo pairs show calving retreat. Calving retreat is far more complex than simple melt.

About the Pedagogy

  • Visual comparisons of changes in glaciers over time is dramatic evidence of environmental change and a good basis for examining possible causes.
  • Activity provides students with the opportunity to investigate for themselves the nature of glaciers.
  • A good set of assessment questions at the end of the activity.

Technical Details/Ease of Use

  • All materials are provided and can be downloaded and printed.

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