TOPICS: Weather, heat transfer, crystal structure
LEVEL: Middle and high school
TIME: One period for field work; additional time before and after field work to discuss predictions and analyze results.
ADVANCE PREPARATION: The activity works best when the air temperature is well below freezing. Students will need clipboard or other flat surface on which to record data outdoors.
NOTE: You may wish to use the Inuit (Eskimo) Snow Terminology sheet from the Snow Terminology activity
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PREDICTION:
In class discussion, encourage creative, logical, and critical thinking. We recommend that you introduce the following ideas if they are not suggested by students: Soil temperature under snow is usually warmer than air temperature. Therefore, the snow is usually warmest near the soil. On sunny days or when the air temperature is near or above freezing, the top layer may be warmest
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PROCEDURE:
Students should work in pairs or larger groups.
QUESTIONS 6-10 require higher-order thinking skills. We recommend that you discuss these questions in class before having students write out their answers
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2.
Answers will vary
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3.
Crystals in the bottom layer are often larger and more widely separated than denser snow layers above
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4.
In general, the warmest layer of snow is the bottom layer, the top layer is the coldest. See Prediction note above
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5.
Soil temperatures under deep snow are usually warmer than air temperatures in midwinter
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6.
The air temperature will directly influence the layer of snow beneath it, as the soil affects the layer snow above it
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7.
The bottom layer of snow is often less dense because it is warmest. Snow near the soil loses water vapor (mass) to colder layers above, increasing the air spaces in the bottom layer
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8.
The air temperature fluctuates daily based on the amount of sunlight received. The soil, when it is insulated by the snowpack, remains relatively constant throughout the winter. It may remain unfrozen throughout the entire winter
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9.
Based on its location next to the soil, the bottom layer is usually the warmest. The layers above provide insulation. The large air spaces and weak linkages between crystals allow small animals to tunnel more easily beneath the snowpack
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10.
The large air spaces and weak linkages between crystals often make the bottom layer the weakest layer in the snowpack. The weight of the overlaying snow layers can cause the snowpack to shear away from a sloping surface, resulting in an avalanche.