By, Louise Huffman, Kate Pound & Robin Frisch-Gleason(with help from the galley staff, McMurdo Station, Antarctica!)
Background:
Ice sheets cover almost all of East and West Antarctica, and most of Greenland. They are as much as 3 km thick. As snow accumulates, it gets buried and turns to ice. The ice flows out from the center of accumulation, and then moves across the landscape under the influence of gravity. The ice follows existing valleys and other low points; eventually it will cover the entire landscape; only the highest peaks might poke through the ice. The ice may also carve its own valleys. The ice may be blocked by mountains. If the ice reaches the ocean it floats on the water as an ice shelf.
Objectives:
To model how ice sheets build up at, and flow away from ice centers. To see how mountain ranges and valleys constrain the movement of ice.
Materials: per student or pair of students:
Clay [for continent]
Small plate, bowl or pan
Corn Starch mixed with a little water [for ice sheet] — check consistency by picking it up
between your thumb and index finger—it should run off like a liquid; tap it with your index finger—it should feel like a solid
Recipe for clay if you don’t have some modeling clay from the store:
1 cup salt
1 1/2 cup flour
½ cup vegetable oil
Water—enough to mix it and make a modeling clay consistency—like thick cookie dough—adjust water
and flour until it is easy to mold—humidity may affect the quantities
Directions:
1. Use the modeling clay to build a continent—give your continent geologic features like mountains and valleys.
2. To represent the ice sheet, place a 5-6 tablespoons of cornstarch mixture in the location that the ice sheet will first start forming. Watch where the ice sheet moves.
3. Add more snow (ice) to the ice sheet by putting more cornstarch mixture at the ice center.
4. Observe where the “ice sheet” moves.
Teachers:
As your students observe the movement of the ice sheet on their continent, lead them in a discussion of the key points in the background information. Then discuss how this model is like a real ice sheet (mountains will constrain it; it will flow out over the ocean and become an ice shelf; continued accumulation can cover landscapes and even mountains, etc.), and how it is not like a real ice sheet (the whole ice sheet is moving and it does not “cascade” like the corn starch mixture will move; ice on the bottom of the ice sheet is under the most pressure and moves the fastest, but in this model that is not apparent).
Key Vocabulary:
Ice Sheet-- a broad, thick sheet of ice covering an extensive area such as a whole continent for a long period of time (Dictionary.com Unabridged (v 1.1)