- empty plastic bottle
- scissors
- cement mix
- ruler
- plastic spoon
- sand
- two large paper cups
- plaster of paris
Cut off the top of the plastic bottle. Fill the bottle halfway with water. Pour in a two inch layer of cement mix. Do not disturb the bottle until the cement is hard. Use a plastic spoon to mix equal parts cement mix and sand in a paper cup. Pour the cement-sand mixture into the bottle to form a layer about one inch deep. Allow this mixture to settle and become hard. Mix equal parts of sand and plaster of paris in another paper cup. Pour this mixture into the bottle to form a layer about one inch deep. After this mixture becomes hard, pour off any water that remains. The hard material inside the bottle is like layers of sedimentary rock.
