TOPICS: Ecology, weather
LEVEL: Middle and high school
TIME: 1 or 2 class periods. Middle school students will require additional time.
NOTE: This activity can be done in any area of undisturbed snow close to school. Students are outside about 10-15 minutes if they are well-organized in advance.
ADVANCE PREPARATION: Label the 4 plastic beakers or bags "top layer", "middle layer", "bottom layer", "compacted snow"
.
MATERIALS:
Use a soil core sampler as a snow core sampler in step B. The snow scoop used in step C is a 365 ml soup or other metal can with both ends removed, with optional wooden handle bolted on. Materials for preserving snowflakes are described on the Snowflake Kit handout
.
PROCEDURE:
Make sure that students understand exactly what they have to do before going outdoors. You may wish to demonstrate the use of the materials before going outdoors, and assign tasks yourself.
QUESTIONS 6-12 require higher order thinking skills. We recommend that you discuss these questions in class before students write out their answers
.
1.
The wind chill equivalent temperature will be lower than the air temperature if there is a wind. The temperature below the snow should be higher than the air temperature
.
2.
The number of snow layers indicates the number of different snowfalls. Ice indicates melting and refreezing
.
3.
Differences may be small. pH of a snow layer depends primarily on the quality of the air through which the snow fell. Each snow layer may have a different pH since each snowfall may have had a different source of air
.
4.
The density of snow is much less than the density of water (1 g/cm3). Typically density increases with depth until the pukak (bottom) layer is reached. Recrystallization results in large ice crystals and large air spaces decreasing density compared to the adjacent layer. A suncrust would have a higher density than a fresh powder snow
.
5.
Snowflakes are hexagonal crystals, modified in shape by environmental conditions
.
6.
The greater the wind speed, the greater the temperature difference
.
7.
To protect yourself wear a hat, gloves and warm boots, and several layers of clothing. Small mammals burrow under the snow
.
8.
The snow acts as an insulating blanket retaining the earth's heat, so that the subnivian temperature is usually higher than air temperature.
.
9.
Compaction, melting and refreezing and sublimation of the snow changes the crystalline structure with depth
.
10.
The pH of a snow layer depends primarily on the quality the air through which the snow fell. Air pollutants depend on the source region of the air. In addition, there may be some ion migration which tends to decrease the pH with depth
.
11.
The bottom layer is typically warmer and less dense than the layer above. Compaction of the snow increases density which increases thermal conduction reducing insulation. The temperature under the snow is likely to fall making the conditions less favorable to small mammals
.
12.
You cannot remove all of the air by packing snow. Maximum packed snow density is about 0.5 g/c3
.
13.
Rodents, deer, rabbits are active during winter. They have fur for retaining body heat.