Abstract
Caves have been used for much more than just exploring throughout Earth's history. Caves have been used for shelter, for religious purposes, and for burial sites. They were even used for food storage, before refrigeration, because they are cool and have constant high humidity. But how are caves formed? What causes those fantastic formations in caves? How do cave formations change as you go deeper in the cave? Get ready for an adventure as you visit a local cave and learn more in this science fair project!Summary
Michelle Maranowski, PhD, Science Buddies
Objective
To learn more about speleology, and to count the number of speleothems versus distance into a cave.
Introduction
What do you think about when you hear the word cave? Do you think about a large, dark, scary place like Batman's Batcave? Caves are actually places of geological wonder and they are a variety of sizes. A cave is defined as an underground void large enough for a human to enter. There are four major causes of cave formation: rainfall, lava, waves, and microbes. There are several kinds of caves, including solution caves, primary caves, sea caves, and glacier caves. Solution caves are formed by dissolution in limestone or in other kinds of soluble rock, caused by rainfall, along with groundwater mixed with carbonic acid (H2CO3) trickling down through limestone to the water table and dissolving the limestone over time. Solution caves are usually formed when the area is under the water table. The solution cave comes to light once the water tables falls. When the water table falls, secondary mineral deposits, known as speleothems, start to grow. As rainwater trickles through the limestone ceiling, it picks up carbon dioxide (CO2) and minerals, such as calcium carbonate. Calcium carbonate is also known as calcite, the main ingredient of limestone, and is derived from marine shells. Water carries the dissolved calcium carbonate through the rock where it hits the air in the cave and hardens. The hardened material collects and forms the speleothem. Stalactites, stalagmites, and helictites are all examples of speleothems.
Figure 1. These are examples of helictites in Jenolan Caves in Australia. Helictites seem to defy gravity because of the way they twist around. (Wikipedia, 2008.)
Primary caves are caves that are formed at the same time as the surrounding rock. An example of this is a lava tube. Instead of dissolving rock, a lava flow will slowly solidify over itself and create a tube. Once the lava flow stops, the lava in the tube drains out, leaving behind the tube. Sea caves are formed by ocean waves hitting a weakened area of rock. Salt water is not as erosive as freshwater so the sea cave is formed by the mechanical process of the wave hitting a weakened cliffside rock.
Glacier caves are formed within a glacier. Water finds its way inside a glacier and melts the ice from within. Air movement can then help enlarge the glacier cave. Another way that glacier caves are formed is through geothermal heat from volcanic vents. An example of this is the Kverkfjoll glacier cave in Iceland. Glaciologists can study glaciers by exploring glacier caves.
Caves do not have direct contact with sunlight. This affects the kind of food found within caves and thus, the kinds of animals you find inside. The variety of animals found in caves can be surprising. Everyone is familiar with bats, but there are also snakes that live in the caves and feed on unsuspecting bats. On the floor in some caves, cockroaches feed on the bat feces, called guano. Troglobites are animals that have evolved to live in darkness. These animals have lost the pigment in their skins and in some cases have also lost their eyes. Then there are bacteria called extremeophiles that can survive in the harsh conditions of certain caves.
In this science fair project, you will investigate your nearest cave system and count the number of speleothems you see in different rooms. Do the numbers and colors change as you move into the cave? What about sizes? Be prepared to be amazed by the speleothems you see!
Figure 2. This shows the Giant Crystal Cave in the Naica Caves in Mexico. Note the man standing in the middle! These giant crystals are made of gypsum. (Javier Trueba/Madrid Scientific Films.)
Terms and Concepts
- Dissolution
- Soluble
- Water table
- Speleothem
- Stalactite
- Stalagmite
- Helictite
- Lava
- Glaciologist
- Troglobite
- Hygrometer
Questions
- How many different kinds of caves are there and how are they formed?
- Where is the largest cave system in the world?
- How many different kinds of speleothems are there? Which one is your favorite and how is it made?
Bibliography
This website has in-depth information about the different kinds of caves and their formations:
- Bewley and Bunnell D. (2008, April 24). The Virtual Cave. Retrieved August 25, 2008.
This website provides a lot of information about caving, or spelunking:
- Wikipedia Contributors. (2008, November 12). Caving. Retrieved November 12, 2008.
This NOVA website has a good animation on how different caves were formed. The root website has information on extremeophiles, as well as some spectacular photographs of the Lechugilla Caves, named by some as the most beautiful cave on Earth.
- Groleau, R. (2002, September). How Caves Form. Retrieved August 25, 2008.
This DVD discusses some of the animals that live in caves. It also has a segment on the Lechugilla Caves.
- Fothergill, A. (Producer), (2006). Caves [Episode]. Planet Earth. [Documentary]. Bristol: British Broadcasting Corporation.
For help creating graphs, try this website:
- National Center for Education Statistics. (n.d.). Create a Graph. Retrieved November 12, 2008.
Materials and Equipment
The first three items listed below are safety gear. Call the authorities in charge of the cave system that you are interested in exploring and ask what other safety items they recommend, require, and have available. You can also visit this Wikipedia article about caving to get more ideas for what you should have:
- Hardhat with mounted light
- Overalls
- Sturdy shoes or boots with good treads
- Backpack
- Pedometer, available from an online supplier such as Carolina Biological catalog #920092A.
- Rope, 10-25 feet in length
- Indoor/outdoor thermometer
- Hygrometer; available from an online supplier such as Carolina Biological catalog #745538. Note this hygrometer includes an indoor/outdoor thermometer.
- Writing utensil
- Lab notebook
- Adult volunteer
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Experimental Procedure
Prior to starting this science fair project, you should do your research and become familiar with the different kinds of speleothems.
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Find a cave with different rooms that you can visit and explore. Before going into the cave, you should do the following:
- Learn how to use the pedometer.
- Make a counting grid from your rope. A counting grid sets up a constant measuring area so that when you go from room to room within the cave you are always measuring within a constant area and then can compare your results. Decide on the kind of grid that you want. It can be a circle or a square. Cut the rope pieces to make a square, or tie the rope to create your circle. Or, you can cut exactly 10 feet of rope, then hold the rope along a wall and count the formations along 10 feet of the wall.
- Pack your rope, pedometer, thermometer, hygrometer, a writing utensil, and lab notebook in the backpack.
- Put on your hardhat, overalls, shoes, and all safety gear.
- Enter the cave with your adult volunteer, who should also be wearing appropriate attire and safety gear, keeping track of how many steps you have taken with your pedometer. Stop in an area where you see interesting formations. Record the number of steps you have taken in your lab notebook. Record the temperature and the humidity of the area in your lab notebook. Do you see any water in this area? Record you observations in your lab notebook.
- Lay out your grid and count the number of speleothems inside the grid. Sort the speleothems you see into categories. Examples of categories are: soda straws, helictites, stalactites, stalagmites, and flowstone.
- Go farther into the cave and repeat steps 2 and 3 two more times in different areas. Record all data in your lab notebook.
- Plot your data on a bar chart. If you need help or would like to make your plots online, try Create a Graph. Label the x-axis with the different categories of speleothems. Make a plot for each area that you visited. Did the number of speleothems change as you moved into the cave? Did a particular speleothem increase or decrease in number as you moved into the cave?
Ask an Expert
Variations
- Take along a set of colored pencils on your next cave trip. In addition to counting and categorizing the speleothems, draw and record the color of the formations. Then research the cause of the colors in the formations.
- Keep your eyes open for the different kinds of animals that call the cave you are visiting home. Did the variety of animals change as you moved into the cave?
Careers
If you like this project, you might enjoy exploring these related careers:
