Model a Moving Glacier

Students make a model of glacier motion and then design an experiment to figure out what affects the speed of a glacier.

Learning Objectives

• Students will learn how alpine (valley) glaciers move.
• Students will learn factors that affect how fast a glacier moves.
• Students will construct a simple model of a glacier.
• Students will make a hypothesis and test it using data collected from a simple model.
• Students will interpret data and present findings.

Materials

Ingredients to make the glacier model material (known as flubber)

• Two containers for mixing
• ¾ cup warm water
• 1 cup white glue
• ½ cup warm water
• 2 teaspoons Borax

Each group will need:

• Large diameter PVC pipes about two feet long, that have been cut lengthwise
• Cardboard boxes or books (to prop up PVC at one end making a slope)
• Ruler
• Permanent marker
• A watch or stopwatch

For part 2 of the activity, students may need some of the following for their experiment:

• Sandpaper
• Vegetable oil
• Water
• Protractor
• Hot water bottles with boiling water and ice water (or a refrigerator)

Preparation

1. Combine ¾ cup warm water, 1 cup of white glue in a container, and mix.
2. In a different container, combine ½ cup warm water and 2 teaspoons of Borax and mix thoroughly.
3. Pour the Borax mixture into the glue mixture. Mix all ingredients with your hands. You will need to lift and turn the mixture to incorporate as much of the liquid as possible.
4. Let the excess liquid drip off and the flubber will be ready for your glacier models.
5. Notes:
   • The flubber can be reused and will keep for several weeks in an airtight container.
   • Safety: White glue is typically non-toxic, but check the packaging of the type you are using to confirm. Borax is harmful if swallowed and the dust from the dry borax can be irritating if inhaled. Ensure students do not eat the flubber and wash their hands with soap and water after using it.

Directions

Introduce students to alpine (or valley) glaciers. Show images of alpine glaciers that illustrate how they fill valleys in many high altitude and high latitude areas. Emphasize that a special characteristic of glaciers and ice sheets is that they move over time, both by internal deformation and basal slip.

Introduce the idea of physical models to students. Models are representations of real-world conditions and can be used to test how the thing that the model represents works. Tell students that they will first make a model of a glacier to see how it moves down a valley (Part 1) and then they will design an experiment to test an aspect of how glaciers move (Part 2).

Part 1: During this part of the activity, students are introduced to the glacier model.

1. Provide each student group (3-4 students) with a piece of flubber, a PVC tube that is cut in half to simulate a valley, and a ruler.
2. Allow students to hold and play with the flubber to get to know its properties. Explain that Flubber is a polymer that has the properties of both a liquid and a solid. The molecules in the flubber are loosely arranged and can slide past each other. Explain that students will use the flubber to simulate glacier ice.
3. Have groups stack books or boxes under one end of the PVC to make a slope for the valley.
   Instruct students to put the flubber at the high end, patting it down to fill the top of the valley. You may wish to have students draw a line across the flubber with a marker to see which part of a valley glacier moves the fastest.
4. Have students monitor the flubber as it moves down the simulated valley, measuring how far it travels with a ruler.
5. Discuss how this model is like a glacier in a valley and how it is not like a glacier in a valley. Remind students that no model is perfect.

Part 2: During this part of the activity, students use the glacier model to test a hypothesis about some aspect of glacier movement. To facilitate this part of the activity with younger students, you may wish to have the whole class work together to come up with a hypothesis and experiment design (steps 1,2, and 3 listed below.)

1. Brainstorm questions with students about how glaciers move, based on reading and introduction. What conditions cause glaciers to move faster? Slower? These ideas will turn into the variables that students test with their glacier models. Examples of some variable that students might choose to study through their model are listed below: (You may wish to guide younger students by providing these options and discussing how each might impact a glacier.)
   • Temperature: All ice is cold, but if the ice in one glacier is colder than the ice in another, will that affect how fast the glacier moves?
   • Slope: Does a glacier in a steep valley move faster than a glacier in a less steep valley?
   • Valley texture: Since glaciers move in part by sliding on their base (a process called basal slip), does the texture of the surface they are slipping on make a difference in the rate of movement? Also, there is evidence that meltwater might lubricate the base of the glacier causing it to move faster. (This is an area of active research.)
2. Making the hypothesis: Have student groups choose one of the conditions that they will test by experimenting with their model and then work together to make a hypothesis out of the variable they are going to test.
3. Designing the experiment: Student groups need to plan their experiment. Emphasize that to test one variable, they will need to keep all other conditions constant. Explain that they will have enough materials to compare two glaciers (i.e., two valleys, two balls of flubber) so designing an experiment that compares conditions would work well. Have student groups outline the method that they will use to test their hypothesis and list all materials they will need in addition to two PVC valleys and flubber. (At this point, you may choose to have student groups turn in their hypothesis and experiment plan so that you can check and ensure that they have a testable hypothesis and a plan that will be able to test the hypothesis.)
4. Testing the hypothesis: Student groups will need to gather the supplies that they need to test their hypothesis. Some of the typical supplies are listed in the materials section above. Students might devise experiments that use other supplies.
   • To test for differences in temperature: one piece of flubber can be cooled by putting it on a water bottle filled with ice water, while the other is warmed by putting it on a hot water bottle before allowing the glaciers to slide down the valleys.
   • To test for differences in valley slope: the two PVC valleys can be put at different angles and the angle of each slope measured with a protractor.
   • To test for differences in texture of the valley: sandpaper can be used to line the valley to add texture. Oil or water can be used on the valley surface to make it slippery.
5. Recording the results: Have a student in each group serve as timekeeper during the experiment and record how far each flubber glacier advances each minute. If time permits, have students repeat the experiment a number of times to see if the results are always similar.
6. Drawing conclusions: Have student groups work together to interpret what they think the results mean.

Communicating the findings: As with any activity in which students experiment to test a hypothesis they have made, this is an excellent opportunity to build communications skills. Have students share their results with the rest of the class through a PowerPoint slide presentation or by creating and presenting a poster

Background

About glaciers:

Alpine glaciers, also called valley glaciers, are found in high mountain valleys worldwide. At lower and warmer latitudes, they occur only at very high altitudes. At higher latitudes, closer to the Poles, they can occur in mountains at lower altitudes too. Glaciers that cover large areas of land and are not confined within valleys are known as ice sheets.

Alpine glaciers are responsible for carving mountains into distinctive shapes leaving pointed ridges between glaciers, u-shaped valleys where the glacier moved through, and hills of rock debris called moraines that were carried in, and pushed by, the glacier. Today, because of rapid global warming, alpine glaciers that are at tropical and mid-latitudes are melting very quickly. Many high latitude glaciers are also in retreat.

Snow that falls on a glacier may eventually become part of the glacial ice. The snowflakes become buried under more and more snow, eventually changing their shape because of the pressure from the layers of snow above and becoming part of the ice. Over time the ice crystals become so closely packed that the tiny pockets of air between them are squeezed out and the ice changes in color from white to blue.

Glaciers are not just giant ice cubes. All that ice can be a powerful force. Glaciers move over time scraping rock from the Earth's surface, bulldozing boulders, gravel, and sand into hills called moraines, and sending ice out over the ocean in massive ice shelves.

Glacial movement:

Under the pressure of its own weight, glacial ice flows downhill over time. The same is true of the flubber in this model. There are two main ways that this happens: (1) by internal deformation and (2) by basal slip.

Internal deformation: The ice moves plastically when under pressure from ice above. Weak bonds between the molecules in the ice allow layers of molecules to slip past each other. So, while glacial ice is a solid, over a long time it flows slowly like honey.

Basal slip: Glaciers also move downhill by sliding at their base. This process is called basal slip. Basal slip can be affected by friction at the base of the glacier. Basal slip can be enhanced if there is water at the base of the glacier. Pressure on the ice that is at the bottom of a glacier can cause some of that ice to melt producing a slippery little layer for the rest of the ice to slide upon. Also, there is evidence from Greenland that melt water can make its way from the top surface of the glacier to the bottom through tunnels in the ice called moulins.

About flubber:

Flubber is a polymer that has the properties of both a liquid and a solid. The molecules in the flubber are loosely arranged and can slide past each other.

If you find that your flubber mixture is too liquid or too solid, you can vary the ratio of glue to Borax. More glue will make the flubber more solid. More Borax will make the flubber more liquid. Make sure that the ratio that you use is consistent for all student groups to eliminate an unwanted effect of different varieties of flubber when students experiment during the second part of this activity.

Extensions

• Consider combining this activity with the Glaciers Then and Now activity.
• Have students take repeat photographs to make a time-lapse record of the flubber glacier flow.
• Discuss how this physical model of a glacier is like and is unlike a real glacier.