Lesson Plan

Explore the world of crystals, fossils, rocks, and caves

Explore the cave with your students
Explore the cave with your students
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Grade Level:
Fourth Grade-Sixth Grade
30 minute classes over 5 days
Group Size:
Up to 36
National/State Standards:
4.P.1.1 Students are able to describe observable physical changes and properties in matter. 
5.P.1.1 Students are able to define matter on the basis of observable physical properties.
speleothems, fossils, geology, cave, formations, crystals, sedimentary, limestone, dogtooth spar, igneous, metamorphic, cave popcorn, boxwork, dissolve, rocks


The lessons included in this short unit help student learn about caves, the formations found within them, and the rocks associated with them.  These are hands on activities which include the making of crystals, fossils, and rock layers. 


Upon completion of the 5th lesson entitled The Formations Wind Cave students 4th through 5th grade will be able to define the word speleothem (cave formations) and describe one of the speleothems of Wind Cave and discuss how it forms.


Water is the critical ingredient in making a cave and the formations found in them. Over the years, Wind Cave has undergone many geological changes. Almost all of these changes have been caused by water. Water created the sedimentary rock in which the cave formed – limestone. Water that seeped through the rock into the cracks formed by the uplift of the Black Hills was able to dissolve the limestone creating the passageways of the cave. The different features that decorate a cave are called cave formations or speleothems; they too were formed by water. The speloeothem Wind Cave is famous for is called boxwork. Geologists believe that boxwork is older than the cave and formed when water dissolved the limestone exposing the boxwork that had been embedded in small cracks in the rock. Today, water continues to seep into the cave. As it does, it leaves behind formations such as popcorn and frostwork and stalactites and stalagmites which are rare in Wind Cave.


Lesson: The Formations of Wind Cave

Goal: To provide students with an understanding of how Wind Cave and some of the speleothems (cave formations) in it were formed.

EE Learner Guidelines:

Strand 1: Questioning and Analysis Skills

Collecting information -- Locate and collect information about the environment and environmental topics

Organizing information -- Describe data and organize information to search for relationships and patterns concerning the environment and environmental topics

Working with models and simulations-- Understand that relationships, patterns, and processes can be represented by models

Strand 2: Knowledge of Environmental Processes and Systems

2.1 The Earth as a Physical System

Processes that shape the Earth -- Identify and explain changes and differences in the physical environment.
Changes in matter -- Identify and describe basic characteristics of and changes in matter.

Targeted learner objectives:

Upon completion of the 5th lesson entitled The Formations Wind Cave students 4th through 5th grade will be able to define the word speleothem and describe one of the speleothems of Wind Cave and discuss how it forms.

State or National Content Standards addressed:

4.P.1.1 Students are able to describe observable physical changes and properties in matter.

5.P.1.1 Students are able to define matter on the basis of observable physical properties.

Lesson description: Through a series of activities students will understand the formation of Wind Cave and some of its decorations.


Lesson Day One – Dripping Crystals


Students will:

·         investigate deposition, the process that allows growth of different secondary cave formations,

·         recognize that different chemical compounds produce different speleothem types,

·         identify several speleothems.



·         2 pieces of cotton yarn or string

·         4 jars or cups of the same size

·         2 saucers

·         Epsom salts

·         baking soda (sodium bicarbonate) or washing soda (sodium carbonate)

·         very warm water

·         spoon or coffee stirrer

·         several books and internet sites about caves and speleothems


On the lesson plan of day 1, two experiments: Rock Candy Crystal and Forming Cave Popcorn will be set up.  Observations will be made by the class each day on the progress of these experiments.

Dripping Crystals


1. Tell the students that they will be conducting an experiment that will demonstrate how water can deposit minerals to create cave formations, or "speleothems" (secondary mineral deposits formed in caves).

2. Ask the students if they have ever seen stalactites or stalagmites. Do they know which is which? Stalactites hang tight to the ceiling and stalagmites come up from the ground and might reach the ceiling someday. How do they form? Discuss how water can carry calcite in solution then deposit the calcite in crystalline form in a cave. If you would like use sugar, salt, Jell-O, or Kool-Aid as examples of minerals dissolving into solution.

3. Explain that the process would take millions of years in a cave. The students will speed up the process in the classroom by using a concentrated solution and sunlight (to aid evaporation).

4. Students may create the set-up, help with it, or watch as you complete the steps. If the students create the set up have them work in small groups.


·      Dissolve as much Epsom salt (or washing soda) as you can in two jars or cups half full of very warm water.

·      Soak a piece of string (yarn) in the solution. Lay the yarn on the jars so that both ends are well inside the solution in each jar and the middle is over the saucer with a dip in the middle.  The closer the dip is to the saucer the great chance you have of creating a column. (Epsom salt creates better popcorn type crystals, washing soda is harder to find, but makes better stalactites.)

·      Put just a touch of dry Epsom salt or washing soda on the saucer. Leave the jars for several days.

5. The solution in the jars will drip onto the saucer, creating a stalactite and stalagmite, and eventually a "column" (when they grow together). Hopefully this will occur… it doesn't happen every time.

6. Set up the second set of jars at the same time, using baking soda instead of Epsom salt. Within 48 hours, the students will notice that the crystals look very different in comparison. The baking soda will form delicate "popcorn" formations along the string.

7. As the students check their experiment each day, discuss the differences between the baking soda and Epsom salt deposits. Why are they different?

10. Discuss what happens when carbonic acid degasses, as it drips or seeps out of a cave wall. Degassing is the process where the acid can no longer hold anything in solution and must deposit it. Why does this cause deposition of calcite?

11. Do you notice crystals in other places than at the dip in the string? Where and why?

12. What property of water allows the string to stay wet and drip water? (Osmosis)

13. Give the students time during class to look at the included reference materials. Have them familiarize themselves with the following formations: stalactite, stalagmite, soda straw, column, popcorn, frostwork, boxwork, and flowstone.

14. Watch the water level in the glasses and discuss formations (speleothems), water levels, groundwater, and recharge. Notice the water level goes down and does not get refilled. Much of the water is being pulled into the yarn. Would this happen in a cave situation? (Yes, the water would drip and go further into the ground.) If there is no recharge, what will eventually happen? What would this mean to the cave system?


Be careful with the Epsom salts. The crystals are very delicate. You will need to add quite a lot Epsom salts and make sure they are dissolved in solution. It will be several days before they crystallize on the string, but they should. If the formation gets heavy, it will break off. Watch the crystallization below the drip it can be rather interesting.

Prerequisite: A basic understanding of dissolved substances and evaporation.

Making Rock Candy


  • 1 cup water
  • 3 cups sugar
  • clean glass jar
  • cotton string
  • pencil or knife
  • food coloring (optional)
  • 1/2 tsp to 1 tsp flavoring oil or extract (optional)
  • Lifesaver candy (optional)
  • pan
  • stove or microwave


1.     Pour the sugar and water into the pan.

2.     Heat the mixture to a boil, stirring constantly. You want the sugar solution to hit boiling, but not get hotter or cook too long. If you overheat the sugar solution you'll make hard candy, which is nice, but not what we're going for here.

3.     Stir the solution until all the sugar has dissolved. The liquid will be clear or straw-colored, without any sparkly sugar. If you can get even more sugar to dissolve, that's good, too.

4.      If desired, you can add food coloring and flavoring to the solution. Mint, cinnamon, or lemon extract are good flavorings to try. The juice from a lemon, orange, or lime is a way to give the crystals natural flavor, but the acid and other sugars in the juice may slow the crystal formation.

  1. While your solution cools, prepare your string. Use cotton string because it is rough and non-toxic. Tie the string to a pencil, knife, or other object that can rest across the top of the jar. You want the string to hang into the jar, but not touch the sides or bottom. You will want to weight your string so it hangs into the container so tie a Lifesaver to the bottom of the string. (Don't use anything toxic.)
  2. You want to 'seed' the string with crystals so that the rock candy will form on the string rather than on the sides and bottom of the jar. To do this, dampen the string with a little of the syrup (dissolved sugar water) you just made then dip the string in sugar.
  3. Once your solution has cooled, pour it into the clean jar. Suspend the seeded string in the liquid. Set the jar somewhere quiet. Cover the jar with a paper towel or coffee filter to keep the solution clean.
  4. Check on your crystals, but don't disturb them. 
  5. You can help your crystals grow by removing (and eating) any sugar 'crust' that forms on top of the liquid. If you notice a lot of crystals forming on the sides and bottom of the container and not on your string, remove your string and set it aside. Pour the crystallized solution into a saucepan and boil/cool it (just like when you make the solution). Add it to a clean jar and suspend your growing rock candy crystals. You can watch a video about making rock candy if you would like to see what to expect at: http://video.about.com/chemistry/How-to-Make-Rock-Candy.htm
  6. When you are satisfied with the size of your rock candy, remove it from the container and then (after examining the crystals) eat it! Ideally you want to allow the crystals to grow for 3-7 days

Lesson Day 2: Learning about Rocks


Different samples of igneous, metamorphic and sedimentary rocks

Almond bark

Candy molds (or aluminum foil made into small containers to hold melted almond bark)

Peanut butter (be careful of allergies) or Jelly

Graham crackers (2 for each student)

Colored taffy (3 pieces for each student)

Waxed paper

Blindfolded rock pass

Instructional procedure: Have students sit in a large circle blindfolded. Pass around various types of rocks such as sandstone, limestone, granite, quarts, and have them feel them. These rocks are going to have a different feel to them. Sandstone will be the roughest and mica the smoothest. Tell the students that the rocks feel different because they were formed differently. Have the students notice the difference in weight and structure of the rocks. Sandstone and limestone are made up of many tiny different particles. These rocks are more easily eroded or carved than the smooth granite  and quartz rocks. Review the difference between igneous, metamorphic, and sedimentary rocks. Sandstone and limestone are sedimentary rocks. Quartz and granite are igneous. Marble is metamorphic.

Edible Rocks Activity:
Tell the class they are going to do an activity showing how the three types of rock are formed. Put the students in groups of four. Give four candy molds sprayed with cooking oil and a plastic spoon to each group. For the first part of the activity, allow the class to gather around the table as you melt the almond bark in a pan on the hot plate. Tell the students that the melted chocolate represents magma. Have them return to their groups, and take the container of "magma" to each group. Allow the students to spoon the melted mixture into their candy molds. While their "igneous rocks" cool, distribute the materials to make sedimentary rocks (peanut butter, crackers, knives), and metamorphic rocks (taffy, waxed paper). The students make cracker and peanut butter stacks to illustrate the layers in their "sedimentary rocks". Each student should then take three pieces of different colored taffy, unwrap them, and stack them on a piece of waxed paper. The student then places the other piece of waxed paper on top of the stack and presses down hard to make "metamorphic rock". To end the activity, call out the name of a rock type and have the students hold up the correct rock model they have made. They can then eat their rock creations.

Instructional method: Hands-on Observation and Discovery

Watch the Making of Limestone

Instructional procedure: Tell students that Wind Cave is formed in limestone and they are going to learn how limestone is made. This 10 minute video is available on Wind Cave National Park website:  http://www.nps.gov/wica/photosmultimedia/cave-video-clips-and-programs.htm  

Instructional method: Film Viewing

Ask the students to write the answers to these questions in their Science notebooks:

  • How can an old rock become a new rock?
  • How is metamorphic rock formed?
  • How are sedimentary rocks formed?
  • How are igneous rocks formed?

Lesson Day 3: How do things dissolve - Disappearing Rocks: Project Underground

Instructional Procedures: Tell students that after the limestone was made some of it was dissolved away to make the rooms and passageways of the cave. Make a pitcher of lemonade for the class to demonstrate how materials can dissolve in water. The limestone of the cave also is dissolved away when it reacts to carbonic acid. Carbonic acid is what is in soda pop that makes it fizz. It is made by mixing carbon dioxide (what we breathe out) and water. Explain that over time the limestone of the cave kept eroding away forming the passageways and rooms we have today.

Give the students different types of rocks, one of them limestone, and a dropper of white vinegar. Have students test the rocks by dropping vinegar on them. The limestone rock will bubble as it is dissolved away, releasing carbon dioxide.

Make a Cave


Students will demonstrate how carbonic acid can slowly dissolve limestone and form caves.


·         A piece of limestone, preferably with an imbedded fossil

·         Water

·         Soda pop, preferably clear


1.      Show the class the example of limestone. Pass it around the room and allow each student to closely examine it. Review how limestone forms.

2.      Ask the students how caves are formed in limestone. (Water dissolves the rock.) Pour water over the limestone. What happens? Do we have a cave? No, we have a wet rock! By itself, water cannot dissolve limestone. What else do we need?

3.      From completing the "Make Carbonic Acid" activity, the students should remember that carbon dioxide in the soil could change the water into carbonic acid. What will happen when carbonic acid seeps through the soil and reaches the underlying bedrock? If this bedrock is limestone (or another carbonate rock), it will slowly dissolve it.

4.      Ask the class where they might find carbonic acid in their every-day lives. Soda pop is acidic because it contains carbonated water, or carbonic acid.

5.      Pour the soda pop over the limestone. Make sure that every student has a chance to see the limestone fizz and slowly dissolve. The soda will fizz on any material, but the acid will dissolve the rock. You could use hydrochloric acid in a demonstration, but if you do make sure the students follow all the safety procedures.

Discuss how carbonic acid can travel through the limestone (via cracks) and create cave passages.

Instructional Method: Hands-on observation and discovery,

Lesson Day 4: Demonstration of boxwork formation.

Instructional Procedure: One of the formations of the cave is boxwork and it was formed very differently from the rest of the cave formations.

Tell the students to use their imagination. Your hand will represent the limestone of the cave. When the limestone was deposited pockets of gypsum were tucked inside. (Put a small amount of soft modeling clay inside your hand so that no one can see) Gypsum is unique and when it gets wet it expands. (Push the modeling clay with your hands so you it pushes out through the cracks your fingers apart to hold it). The gypsum expanded and cracked the limestone, like your fingers are spread apart. Tell students that as the gypsum continued to expand it filled in all the cracks it had made in the limestone. Over time, the gypsum turned into something called calcite. Over more time the limestone, when the cave filled with water, the water eroded the limestone away, (refer to previous activity) and exposed the boxwork. (Remove your fingers from the soft modeling clay and hold it up for the class to see) We are left with the calcite fins we call boxwork today. For a picture of boxwork, visit the park's website at http://www.nps.gov/wica/naturescience/speleothems-boxwork.htm

Instructional Method: Observations and models

Lesson Day 5: Forming Cave Popcorn (continued from day 1)

Instructional Procedures: - Popcorn

Explain to students that as the water evaporates from the string the baking soda is left behind and more water and baking soda is pulled from the jar. As more water evaporates more baking soda is left and the crystals grow larger. Students will finish their observations of the growing speleothems and write a summary of their formation.

Small, knobby growths of calcite on the cave walls are called cave popcorn. Popcorn commonly forms in one of two ways in the cave: where water seeps uniformly out of the limestone wall and precipitates calcite; or, when water drips from the walls or ceilings of the cave and the water splashes on the floor or on ledges along the walls. This splashing action causes loss of carbon dioxide and the subsequent precipitation of calcite. Visit http://www.nps.gov/wica/naturescience/speleothems-cave-popcorn.htm to see an example of cave popcorn.

Instructional Method: Hands-on Observations and Discovery, Primary Data Collection

Instructional procedure: Rock candy and dog tooth spar

Take out the rock candy that the class started the previous week. Explain to the students that the sugar which was dissolved inside the water formed the crystals as the water evaporated. Have students make their last observation. Pass out pieces of the candy to each student to have.

Dogtooth spar is a speleothem found in limestone caves. They are calcite crystals that resemble dogs' teeth (hence the name). In Wind Cave the sharply tooth-shaped crystals are often found in open space including veins, fractures, and geodes.  For an example of dog tooth spar visit: http://www.nps.gov/wica/naturescience/speleothems-dogtooth-spar.htm

Instructional Method: Hands-on Observations and Discovery, Primary Data Collection

Bibliography of sources used:   

Zokaites, Carol. Project Underground: A Natural Resource Education Guide. Richmond Virginia: Richmond Areas Speleological Society,1993.

Wind Cave National Park "How to Make Limestone." http://www.nps.gov/ wica/ National Park Service.

Background information (to see examples of the different types of rocks visit: http://geomaps.wr.usgs.gov/parks/rxmin/rock.html)

Sedimentary rocks form when layers of sediment (clay, sand, gravel, and minerals) settle to the bottom of the ocean and then compact (press together by the weight of additional deposits) and cement together. Examples: limestone, gypsum, rock salt, and sandstone. Fossils are often found in sedimentary rock.

Igneous rocks originate from the cooling and solidification of molten rocks. Igneous rocks are formed underground or above ground. Underground, the molten rock is called magma. As the magma cools underground the magma becomes igneous rocks, often a form of granite. When the magma rises above the earth surface such as when a volcano erupts lava is formed. Examples: quartz, granite, pegmatite, pumice, obsidian, and lava

Metamorphic rocks are rocks that have changed or "morphed" into another kind of rock. They're formed from igneous and sedimentary rocks lying deep below the Earth's surface that are subjected to high temperature or pressure or some type of chemical reaction. This causes the rocks' crystal structure to change.  Examples: Limestone becomes marble, shale becomes slate, and granite becomes gneiss.

Park Connections

Wind Cave National Park is open all year and teachers can bring students for regularly scheduled cave tours any time. Teachers may request a program that supports a particular classroom objective for any of the cave tours.  To make a reservation for a cave tour call the park at least 3 weeks in advance at 605-745-4600.  Check the park's website for tour schedules.  The park also features an environmental education program called Connections in late April and early May.  Reservations for this program may be made early in March - call the park for more information.  


To learn more about the other caves visit the National Park's Cave and Karst Resources Management Website at  http://www.nature.nps.gov/geology/caves/

Additional Resources



speleothems, fossils, geology, cave, formations, crystals, sedimentary, limestone, dogtooth spar, igneous, metamorphic, cave popcorn, boxwork, dissolve