Dripstones: What are Stalactites and Stalagmites? (page 2)
- Further demonstrate how high humidity affects the growth of the crystals by preparing the cups as in the original experiment. Place the cups at each end of a see-through plastic storage box. Pour enough water into the box to cover the bottom with a thin layer of water. Cut a string long enough so that it reaches between the cups and hangs about 1 inch (2.5 cm) above the water's surface. Tie a washer to each end of the string. Wet the string as before, then place one washer in each cup. Cut a piece of black construction paper to cover a saucer, then place the saucer under the center of the string. Place the lid on the box. Set the box where it will not be disturbed. Observe the string every day for 7 days. Make daily drawings to use as part of the project display.
- Demonstrate low humidity by repeating the above procedure, but replace the water with borax (a powdered water softener found at the grocery store). Borax will absorb water from the air, making the air around the string dry.
- Caves are usually cool. In addition to humidity, does temperature affect the growth of the crystals? Repeat the previous experiments, preparing two boxes, a high-humidity box with water and a low-humidity box with borax. This time, place the boxes in a section of the refrigerator where they will not be disturbed. Carefully remove the boxes and make observations once a week for 2 to 3 weeks.
Check it Out!
- Dripstones are also called speleothems from two Greek words meaning "set down in caves." Use earth science texts and encyclopedias to find out more about speleothems. What are 43 the shapes of speleothems that are called columns, soda straws, helicitites, flowstone, and cave pearls? How are these structures formed?
- The calcium carbonate in speleothems is generally in the form of the mineral calcite. Sometimes the calcium carbonate forms aragonite crystals. Find out more about calcite and aragonite. How do these minerals differ? What is the difference in the appearance of speleothems formed by these minerals? What type of formations in caves are produced by other minerals, such as gypsum and epsomite?
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