|Geology Rocks |
These activities align with the following National Science Education Standards: Content Standard D: Earth and Space Science—Changes in the earth and sky; structure of the earth system; earth's history.
The Rocky Mountains can serve as a primer on geologic activity for you and your students. Crustal movements, including folding, uplift, and volcanic activity, helped to create the high peaks, many of which are more than 4,000 m high. Forces of weathering and erosion went to work almost immediately and continue to shape the mountains today. In the following activities, which can also be performed as teacher demonstrations, you and your students can investigate some of the complex geologic processes that helped shape the Rocky Mountains.
Shaking It Up
- ½ cup of small rocks—rough, not smooth (less than 3 cm in diameter)
- sturdy plastic container with top, capable of holding the rocks and approx. 1 ½ cups of water
- balance scale
- stopwatch or timer
Time required: Overnight preparation of rocks; one class period or less
1. Place the rocks in the container, add the water, and soak overnight.
2. Pour the water and rocks through the strainer, and then weigh the rocks. Note the weight on the chalkboard or have students make note of it in their journals.
3. Put the rocks and more water back into the container. Cover tightly.
4. Have the students take turns shaking the rocks and water, with each student shaking for about 2 minutes.
5. After a total of 20 minutes of shaking, strain the rocks and water again. Rinse the rocks.
6. Weigh the rocks again, and compare their weight with the previous measurement.
7. Ask students to explain what happened. (They should conclude that the tumbling action caused by the shaking caused tiny pieces of the rocks to come off—the same weathering action that occurs in a fast-moving mountain stream, for instance.)
It's All Downhill
- 3 metal baking pans, approx. 20 x 30 cm
- a mixture of soil and gravel—approx. 2 cups of soil and 1 cup of gravel for each pan
- water in a plastic squeeze bottle
- 2 or 3 wooden blocks—each about 3 cm high (books also work)
Time required: One class period
1. Place the soil and gravel mixture into one end of each of the baking pans to a depth of about 3 cm, as illustrated.
2. Take one of the blocks and place it under the soil-and-gravel end of one pan. This represents a low hill.
3. Squeeze water from the bottle in a slow, but steady, stream onto the top of the soil-gravel hill. Observe what happens.
4. Under the soil-and-gravel end of the second pan, place two blocks one on top of the other, thereby increasing the elevation of the hill. Again, squeeze water from the bottle, attempting to keep it flowing at the same rate as in step 3.
5. Repeat step 4 with another block underneath the end of the third pan, making the hillside even steeper.
6. Have students explain how the steepness of the hillside affected the rate of erosion.
Glaciers at Work
- Sand—approx. 2 ¼ cups
- Gravel—approx. 1 cup
- Water—approx. 1 cup
- small paper cup—approx. 175 mL
- access to a freezer
- metal baking pan—approx. 20 x 30 cm
Time required: Overnight preparation of "glacier" and then intermittent observations over a period of several days as the "glacier" melts
1. Add equal amounts of sand and gravel to the paper cup to a depth of about 3 cm. Mix together well.
2. Add water to the cup to within about 2 cm of the top. Place the cup in the freezer overnight.
3. When you're ready to begin the experiment, place two cups of sand in the baking pan and add a small amount of gravel and enough water to make a "mountain."
4. Remove the cup from the freezer, peel off the paper, and place the frozen mixture (your "glacier") ice side up on top of the mountain.
5. Observe what happens as the glacier melts. Where do the rocks (the gravel) in the glacier go? Does the mountain change in appearance?