Land Ice

Part C: Make a Glacier

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Image courtesy of Leigh Stearns, University of Kansas.

Provenance: Image courtesy of Leigh Stearns, University of Kansas http://www.people.ku.edu/~stearns/leigh/page2/page15/flubber.html
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Ice is a special substance. Under steady pressure, such as that exerted by the weight of a glacier, ice will bend and flow. Under a lot of stress, ice will break. This is how crevassescrevasse: deep crack in an ice sheet or glacier. form in glaciers. From your chemistry class, you may recall that at a molecular level ice consists of stacked layers of hydrogen and oxygen molecules connected by relatively weak bonds.

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Crystal structure of hexagonal ice. Grey dashed lines indicate hydrogen bonds. Image source: Wikipedia

Provenance: Image source: Wikipedia (http://en.wikipedia.org/wiki/File:Hex_ice.GIF)
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Ever play with silly putty? This stretchy substance actually bends and flows very much like ice, and therefore makes an excellent medium for simulating the movement of glaciers. In this part of the investigation, you will make a model glacier out of homemade silly putty, sometimes called goo, gak, or flubber.

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1. Make the glacier gak.
   • In the first mixing bowl, combine 3/4 cup warm water and 1 cup glue. Stir until well mixed.
   • In the second mixing bowl, combine 1/2 cup warm water and 1 tsp of Borax powder and stir until the powder is fully dissolved.
   • Combine the contents of the two mixing bowls, and stir until a glob forms.
   • Put half of the glob back into the first mixing bowl. Add a few drops of food coloring.
   • Use your hands to knead the mixture in each bowl until it is well mixed (approx. 2-3 minutes). Wear rubber gloves to prevent staining your hands with the food coloring.
   • Break off pieces of the white gak and pieces of the colored gak. Lay them out in strips of alternating color. Smush the strips together to reform a single striped glob of gak.
2. Get a feel for the properties of the gak. Stretch it slowly. Pull on it quickly. How does it behave?
3. Prop up one end of the PVC pipe chute with books so the glacier will be able to flow downhill.
4. Place the entire "glacier" at the top of the chute. Use the dry erase marker to mark the position of the front end of the glacier (the terminus).
5. Set your timer for 5 minutes.
6. Mark the new location of the glacier terminus.
7. Measure the distance the glacier traveled from start to finish at the center, the left side, and the right side of the glacier.
8. Determine the rate of flow for all three by dividing distance by time. (Distance glacier traveled (cm) / Time (in seconds) )
9. Record your results.
10. Set up the experiment again, marking the terminus of the glacier.
11. Set your timer for 5 minutes
12. Poke the plastic drinking straw through the glacier as close to the top of the glacier as possible.
13. Add 5ml of water through the straw to simulate meltwater seeping down through the glacier.
14. Predict how you think the glacier will flow compared to the first time you ran the experiment.
15. Measure the distance the glacier traveled from start to finish at the center, the left side, and the right side of the glacier.
16. Determine the rate of flow now that you added water, and record your results.