In Part A: Students begin by reading this excerpt about land ice (Acrobat (PDF) 305kB Jul2 11) from the NSIDC page All About the Cryosphere. They then explore glacial accumulation and ablation processes using an online interactive produced by the University of Kentucky that shows them how scientists are able to determine whether a glacier is growing or shrinking and whether changes in the glacier's mass balance are related to climate change.
Time estimate: 25-50 minutes
In Part B: Students read a short background essay and watch the NOVA Science NOW video Fastest Glacier (running time approximately 5 minutes). They then do a simple experiment that demonstrates how a layer of melted water acts as a lubricant that speeds up glacial movement. This experiment can also be done by teacher as a demonstration at the front of the class. As a class, discuss the content of the video and how it relates to the experiment/demonstration.
Materials:
- Small wooden block
- ice cube
Encourage interested students to explore more about how scientists measure the speed of glaciers by watching the video in the How Do We Know What We Know? section. Time estimate: 50-75 minutes
In Part C: Students make a model glacier out of homemade silly putty, sometimes called goo, gak, or flubber. You will need the following materials for each group of students:
- Borax powder
- water (cold/room temperature, warm, & hot)
- white glue
- 2 mixing bowls
- popsicle sticks, for stirring
- food coloring
- rubber gloves
- airtight container or ziplock bag
- chute made from PVC Pipe or cookie sheet (Also, the suggestion to use a short piece of plastic rain gutter for the chute is one that came from teachers. An 8-foot or 10-foot section of rain gutter is very inexpensive and easy to cut up into 2-foot lengths for students just with a good pair of scissors. And for a slow-moving glacier, a 2-foot section would be plenty long.)
- books to prop up chute
- dry erase marker
- ruler
- timer
- plastic drinking straw
- 5 ml water
If you'd like to have students compare the effects of different glacier flow rates, have them play around with the proportions of Borax and water in their gak recipe. Here are two tested recipes:
Recipe 1 (faster-moving):
- 1 tsp Borax powder
- 1 & 1/4 cup warm water
- 1 cup white glue
To make the gak:
- In a mixing bowl, combine 3/4 cup warm water and 1 cup glue. Stir until well mixed.
- In a 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.
Recipe 2 (slower-moving):
- 2 tsp Borax powder
- 4 oz. hot water
- 2 oz. cold or room temperature water
- 1 cup white glue
To make the gak:
- In a mixing bowl, combine the glue & 2 oz cold/room temperature water. Stir until well mixed.
- In a second mixing bowl, dissolve borax in hot water & slowly add it to glue mixture—working quickly, as the mixture will thicken.
- 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.
Time estimate: 50-75 minutes
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