Activity Summary
This activity takes a closer look at limestone cave geology and hydrology, using a cutaway drawing of a cave system. Students will learn additional cave vocabulary, and consider the implications of underground structures on planning human communities.

Educational Goals

1. Students will be able to:
   • Define dry cave, wet cave, underwater cave, sink hole, shaft, and water table.
   • Describe at least two ways that pollution can enter cave systems.
   • Explain why it is important for communities in limestone areas to map their cave formations.
2. Students will be able to explain that bats are not blind, and how they use sonar to navigate in the dark.

Background
Caves and cave animals figure in numerous popular stories. Why? There are many reasons. Caves have often served as secret hiding places for people, treasures, or other secrets. As recently as the Civil War, cave minerals were used secretly to make ammunition in caves. Caves are inherently dangerous. Their darkness guarantees both danger and mystery.

Caves also offer extraordinary beauty, as any geologist or caver will testify. The bizarre shapes and colors fascinate people of all ages. Then, of course, there are bats, providing a rich lore of legend in nearly every culture. Oddly enough, in our culture, the legends have built up around vampire bats. Vampire bats are found only in the American tropics and are a tiny fraction of all bat species. In China, on the other hand, graphic symbols of bats represent good luck rather than evil. To prepare for this activity, please consult the List of Multimedia Resources. See what you can find in your school and local library.

In many children's stories, caves bring together all the elements of good stories:

• interesting characters
• mystery, hidden things
• unusual and bizarre animals
• history and legend
• bizarre shapes, colors, smells
• danger.

Materials Provided

• Click to download Handout 5: Cave Diagram (gif image)
  (Diagram shows polluted stream runs down to the sinking stream and into a wet cave. Also shows sink holes, shaft, tunnel, dry cave, and underwater cave.)

Procedure

1. Ask the question: Why is cave mapping important? Discuss answers.
   (Maps prevent cavers from getting lost. They also keep road and building constructors from building on sink hole areas, and maps help prevent pollution of underground water.)

2. Distribute copies of Handout 5: Cave Diagram. Locate and discuss new features that have not been discussed before:

   Dry cave: a cave with no standing water or streams.

   Tunnel: a long, narrow, horizontal passage.

   Shaft: a long, narrow, vertical passage, going up and down or sloped, which may require special climbing equipment. Vertical shafts are often located at the bottom of sink holes.

   Sink holes: places where a cave used to be near the surface. When the limestone roof of the cave collapses, a sink hole is created. On the surface, a sink hole might just look like a steep hole. (Note: one sink hole is labeled. Ask students to locate the others.)

   Sinking stream: a stream suddenly disappears underground into a cave system.

   Water table: the level below which all openings in rock are filled with water.

   Wet cave: a cave with underground standing water, seepage, streams, or ponds.

   Underwater cave: a cave that develops below water level. Cave divers explore these caves.

3. Ask students to use a blue crayon to trace all the ways that water can get into the caves. Remind them that water will seep through soil. Ask them to color all bodies of water above and below ground.

   Use a red crayon to show how pollution could move from the factory, through cave passages, to the ocean.

4. Ask students to identify underground features that could be dangerous to people.

   Sink holes: If people do not have good cave maps, they won't know where sink holes are developing. Because of this, many houses, roads, animals, and farmlands have fallen into sink holes.

   Shafts: Good cave maps will show where shafts are. Cavers can use climbing equipment to get in or out of shafts. Maps will also keep people from falling into shafts in caves.

5. Ask students to identify dangers to caves.

   Sinking streams: If streams are polluted, they can carry pollution to cave fish and other animals. Pollution can come from houses, from factories, and from roads.

   Sink holes: Many people use sink holes for dumping garbage. Pollution from garbage can harm cave animals.

6. Ask the students what they would change about the drawing if they were in charge of where to build factories, houses, and roads. Discuss.

Discussion Questions

1. If bats are not blind, how do they find their way in the dark?
2. Why are no two caves the same shape?

New Words for Lesson 2.3

Grade Level	Volcabulary
All grades	diagram, dry cave, wet cave, underwater cave, shaft, sinkhole, sinking stream, pollution, water table
Kindergarten	wet, hole
Grade 1	dry, stream
Grade 2	danger, tunnel, diver
Grade 3	sink, pollute

Writing Assignment: Grade 2-3

1. Think about the different openings where water goes underground. What happens next? Write a paragraph describing how rainwater gets into a wet cave.
2. Think about how bats "see" in the dark. Explain how bat sonar works.

All USGS teaching packets are based on National Education Standards.