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Cavern Geography
Because the dissolution of limestone takes place under the surface in the bedrock, a cavern may not have an entrance. Most entrances are formed after a cavern is formed. Entrances may be created by a valley enlarging and exposing a section of the cavern on the side of a hill, the collapse of a sinkhole, or the intrusion of man's developments into the surface.
Limestone caverns are commonly found in karst terrain. Karst comes from the Slav word krs meaning crag or stone. The word became a term to describe the rocky region along the Dalmatian coast of the Adriatic Sea. Karst terrain is generally characterized by bare rocky ground, sinkholes, underground rivers and the absence of surface streams and lakes. It should be noted that a karst area does not necessarily contain a lot of caves and at the same time an area with extensive caves may have little karst terrain.
Experiments & Activities
Grades K - 4 "Dissolution Experiment"
Materials
- 27 or more sugar cubestoothpicks
- A clear fish tank with straight sides
- 1 spray bottle with water
- 2 lbs. modeling clay
Procedure
- Stack the sugar cubes against the inside of the fish tank. Make the structure at least four cubes high and wide, and three deep. For a more realistic look, a few columns may have one or two more cubes. Explain how the sugar cubes represent large areas of limestone and the spaces between the cubes represent the natural cracks and fissures in the limestone through which water travels.
- Cover the sugar structure with approximately 1/8-inch of clay. Make sure there are no gaps. The clay represents the surface dirt.
- Using the toothpick, poke several holes through the clay into the sugar. This will allow water to seep through.
- If needed, you can explain dissolvability by dissolving salt or sugar in a glass of warm water.
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