Activity time: 20 minutes
Materials for Activity
- Clear plastic cups (about 3 inches deep/3 inches wide), two for each participant
- Modeling clay
- White play sand and several containers and scoops
- Aquarium gravel (natural color), a large colander, and several containers and scoops
- Pitcher(s) of clean water
- Food coloring, blue or red
Preparation for Activity
- Rinse the aquarium gravel in the colander to remove powdery residue which could cloud the water in the cups. Pour aquarium gravel into containers for participants to share. Set containers on work tables.
- Pour play sand into containers and place on work tables.
- Place food coloring and modeling clay on work tables for participants to share.
- Pour cups of water for all participants and set aside (so participants will not drink them).
- Set an empty cup for each participant.
- Make an aquifer to provide a model for participants and to increase your confidence leading this activity.
Description of Activity
Gather participants at work tables. Tell them they will make aquifers and see how the ground holds water. Show the group the aquifer you have made.
Invite participants to take an empty cup and pour white sand on the bottom, about 1/4 inch deep.
Distribute the cups filled with water. Instruct participants to pour enough water into the sand in their aquifer cup to wet the sand completely but leave no standing water on top of the sand.
Let participants see how the water is absorbed. They will notice that the water remains around the grains of sand. Suggest participants gently shake or tap their cup to level its contents.
Now invite participants to make the second layer of their aquifer with modeling clay. Tell them to pinch a small piece of the clay into a thin, flat disc that can cover about half the sand. Ask them to lay the disc on the sand and press one edge of the clay up against the side of the cup to make a tight seal. Check to make sure all participants have a good seal. This clay will represent a "confining layer"-compacted rock and soil that keeps water from passing through. Invite participants to pour a very small amount of water onto the clay. Draw their attention to how water sits on top of the clay.
Now invite participants to form a third layer, using the aquarium pebbles. Place the pebbles over the sand and clay, covering them completely. Suggest they slope the rocks to form a hill on one side of the cup and a valley on the other.
Explain that the layers in the cup represent some of the many layers of the Earth's surface.
Now invite participants to pour water into their aquifers until the water in the valley is even with top of the hill. Instruct them to watch as the porous aquarium pebbles allow water to flow and sit between them. Soon each cup should contain a small lake as well as ground water. This is a model of how the earth holds water above and within the ground. A well works because it is a hole through which ground water can be pumped to the surface.
Invite participants to use the food coloring to see how garbage, pollution or a chemical spill can affect ground water. Ask them to put a few drops of food coloring on top of their rock hill, as close to the inside wall of the cup as possible. and observe what happens. They should see the color spread through the rocks, then to the surface water and finally through the "ground" water into the white sand at the bottom of their cup.
Help participants understand that pollution or contamination of land and even air can pollute the Earth's water. Adults in the group may remember crises around acid rain, where air pollution from coal burning fell as rain into lakes and killed many fish. Others may be familiar with the story of Erin Brockovich, who uncovered corporate chemical dumping that contaminated ground water and made area residents very ill. Cleaning up our environment helps all of us live healthier lives.
Leave some time for clean-up. You might have participants add their unused clean water to your chalice bowl. Recycle used plastic cups.
Including All Participants
Some participants, such as young children, may lack the fine motor skills to build this aquifer. You could have mixed-skills or -age groups work together.