Pressure and Ice
Process Skills
Focus on Earth Science Teacher Resource Book, 1987, Merrill Publishing, Columbus, OH.
observing
measuring
interpreting data
forming hypotheses
separating and controlling variables
experimenting
formulating models
Focus on Earth Science Teacher Resource Book, 1987, Merrill Publishing, Columbus, OH.
Problem: How does pressure affect ice?
Materials
2 pie pansbrickice cubesclock or watch
Preparation Notes: This activity may also be done as a demonstration. You may want to freeze some sand into some of the ice cubes. The ice around the sand exposed at the edges of the cube will melt faster, as the sand warms due to pressure.
Procedure
1. Put an ice cube in each pan.
2. Place the brick on top of one ice cube.
3. Record the time.
4. After 15 minutes, measure the amount of watercollected in each pan.
Questions
1. Which cube melted faster? Why? The cube under the brick melted faster due to increased pressure.
2. What causes pressure in a glacier? In a glacier, pressure is caused by the weight of the ice.
3. Where in a glacier does the ice melt because of pressure? at the bottom
4. How does pressure affect the melting of ice? Pressure increases the rate at which ice melts.
Glacial Plucking
Process Skills
Focus on Earth Science Teacher Resource Book, 1987, Merrill Publishing, Columbus, OH.
observing
inferring
interpreting data
formulating models
Focus on Earth Science Teacher Resource Book, 1987, Merrill Publishing, Columbus, OH.
Problem: How does ice wedging aid glacial erosion?
Materials
Focus on Earth Science Teacher Resource Book, 1987, Merrill Publishing, Columbus, OH.
test tube
coffee can
crushed ice
spoon
metric ruler
salt
water
glass marker
Focus on Earth Science Teacher Resource Book, 1987, Merrill Publishing, Columbus, OH.
Preparation Notes: Caution students to wear their goggles when crushing ice.
Meeting Needs: Adding food coloring to the water may help visually impaired students see and measure the water line in the test tube.
Preparation Notes: This activity may also be done as a demonstration. You may want to freeze some sand into some of the ice cubes. The ice around the sand exposed at the edges of the cube will melt faster, as the sand warms due to pressure.
Procedure
1. Fill the coffee can half full of crushed ice.
2. Sprinkle about two tablespoons of salt over the ice and stir the mixture.
3. Fill the test tube half full of water. Mark the height of the water on the side of the test tube with the glass marker.
4. Place the test tube in the salt-ice mixture.Be sure that the tube is surrounded by ice and that ice comes up to the top of the tube.
5. When the water in the tube freezes, mark the height of the ice.
Questions
1. What happens to the volume of water as it becomes ice? It increases.
2. What happens to cracks in rocks if water freezes in them? Cracks expand as water freezes to accommodate ice's large volume.
3. How is the freezing of water in fractured rocks related to glacial plucking? Water freezesin cracks in fractured rocks. As the glacier moves away from the valley wall, the rock is taken along with the glacier.
4. How does the freezing of water help glaciers erode bedrock? When meltwater penetrates cracks in the bedrock and freezes, the rocks break off and are carried by the glacier. These rocks then abrade and scour the bedrock over which the glacier moves.
Focus on Earth Science Teacher Resource Book, 1987, Merrill Publishing, Columbus, OH.