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Caves.

Caves are deep mysterious holes under the ground. Some are huge in size. The insides of caves are damp, dark caverns where sunlight never enters.

It is said that the inside of a cave is so dark, you can almost "hear" the darkness. In the pitch blackness of a cave, many beautiful and strange rock formations are continuously being created. This wonderful world of underground rocks, lakes, and even waterfalls may never be seen, unless someone discovers the cave.

How Caves Form

Caves are formed when underground water fills in a rocky area. Slowly, drip by drip, the rock is dissolved away. When the water level drops, all that is left is a large, empty hole. This natural hole is a cave.

Even after the ground water lowers and a cave dries out, water from the surface above continues to seep down through cracks in the rock. This seeping water picks up carbon dioxide from the air and ground and forms a weak acid. Most caves are formed in rock that dissolves easily, like limestone. Limestone is made of the mineral, calcite.

Fantastic Formations

Many of the unusual rock shapes found in caves are made when small amounts of water, containing dissolved rock, slowly drip down into the cave. Rock formations made from dripping water are called dripstone. Sometimes the dripping water just reaches the roof of a cave and then starts to evaporate. When this happens, all that remains is the dissolved rock attached to the cave ceiling. This is called a stalactite.

Sometimes, water drips down to the cave floor. When the water dries up, it leaves many unusual rock shapes called stalagmites. When a stalactite and stalagmite meet together, they form a column. These dripstone rock formations grow very, very Slowly - only about 1 inch (2.5 cm) every hundred years. It takes thousands and thousands of years for dripstones to form.

There are many other types of rock formations in caves. Flowstone looks like a rock waterfall. It is made when a thin layer of water flows over cave walls and floors, leaving a sheet of minerals. Drapery are thin layers of rock that hang from the cave ceiling and look like curtains. Others are called fried eggs, popcorn, cave pearls, and soda straws, because that's just what they look like!

Background

The dark, wondrous, and mysterious world of caves is a territory few of us ever get the opportunity to explore. By definition, caves are naturally occurring holes in the earth that extend past the point where sunlight can reach. Caves take thousands and thousands of years to form. Some caves consist of only a single chamber, while others are part of a vast interconnecting network of passages and caverns. In this dark wonderland, an incredible treasure trove of unique, and often very unusual, geological formations, waterfalls, and underground lakes can be found. Scientists who study this fascinating underground world, and the organisms that live there, are called speleologists (spee-lee-ahl-ehjests) after the study of caves - speleology. Enthusiasts who enjoy exploring and mapping caves as a hobby are called spelunkers.

How Caves Are Formed

The earth is made up of many different types of rocks. One that is found in great abundance is limestone. Limestone is made primarily of the mineral calcite, which is chemically - calcium carbonate. The formation of limestone occurs in areas that were once covered by water, but have dried out. At the bottom of these areas are layers of the fragmented shells of the many water organisms that once lived there. Numerous layers of soil and sediment eventually covered these layers of tiny broken shells. Over long periods of time, the pressure of the top layers on the shell layers below, formed sedimentary limestone rock.

Caves are usually formed when water seeps down through the soil and cracks in rocks, and finally reaches an area containing deposits of limestone. As rainwater falls to the ground, it picks up small amounts of carbon dioxide from the air and forms a weak acid called carbonic acid. As this water flows down through the earth, it picks up more carbon dioxide from decaying plants and animals in the soil, increasing its acidity. Finally the water reaches the saturated area below the surface of the ground called the water table, where underground rivers flow.

After thousands of years, huge caverns are formed where the acidic water has dissolved away large areas of limestone rock (or other types of rock like dolomite or gypsum). When the water table lowers, all that is left is a hollow open rocky chamber, which we call a cave. Though most of the world's caves are solution caves formed through this process, some caves are formed by wind or wave erosion, or by volcanoes or earthquakes.

Fantastic Formations

Even after the water table drops, many caves remain moist. This is because water from the surface of the earth continues to make its way down through the soil and rocks. Many caves contain underground waterfalls and shimmering lakes. This seeping water from above is also responsible for the many beautiful and unusually shaped rock formations found in caves. These natural geologic "decorations" are called speleothems or dripstones. Dripstones are formed the action of that contains dissolved rock.

After the water evaporates, all that remains is a rock formation, usually in a strange or odd shape. Dripstones that form from the cave ceiling are called stalactites. Dripstones that form on the floor of the cave are called stalagmites. When a stalactite and stalagmite meet together, they form a rock column.

The three main factors that influence the speed at which cave formations grow are: a) the amount of dripping water, b) the amount of calcite dissolved in the water, and c) the amount of humidity in the cave. If there are high levels of dripping water and dissolved calcite, the speleothems will form more rapidly. If the cave is very humid, it will slow down their formation, because evaporation will be slower.

As long as water from the surface can reach a cave, it is referred to as a live cave, because new formations can be created. Once water stops reaching a cave, it becomes a dead cave and its formations slowly begin to erode away.

Types of Cave Formations

There are many spectacular forms of speleothems including:

* Flowstone: This looks like a rock waterfall and is formed when a thin film of water flows over cave walls and floors, leaving a sheet of minerals.

* Popcorn: These rock formations look like popcorn and are sometimes called "sea grapes." They form when moist cave air (containing dissolved calcite) evaporates around very rocky areas.

* Drapery: These are thin sheets of rock that hang from the cave ceiling and look like curtains. They form when water drips in an irregular path down an angled surface.

* Fried Eggs: The egg "whites" of these formations are the bottoms of broken stalagmites. The yellow "yolks" are calcite mixed with other minerals.

* Gypsum Flowers: These flower-like formations are strange spiral-shaped crystals that sprout from some porous rocks.

* Cave Pearls: These are underwater calcite deposits that harden around pieces of sand.

* Soda Straws: These very thin stalactites have hollow centers. As water flows down the inside of these formations, it brings more and more dissolved calcite to the ends of the hanging "straws."

* Shelfstone: These unusual rock formations are arranged like an over-lapping series of shelves.

* Helictites: These are some of the most beautiful speleothems. They are strangely twisted crystal structures that can spiral out from cave floors, walls, ceilings, or other formations.

Cave Life

Many different organisms live in caves. Caves are divided into three zones based on the amount of light that reaches them.

* Entrance Zone: The entrance zone houses a large variety of plants and animals. Many animals go into these areas for protection or to hibernate. They leave the caves to search for food. An animal that goes in and out of a cave is called a trogloxene (meaning cave visitor). Bats, bears, wild cats, porcupines, snakes, raccoons, mice, rats, moths, frogs, and birds are all trogloxenes. This area is also home to mosses, mushrooms, and some other plants.

* Twilight Zone: In this zone, the light is much dimmer. Troglophiles (meaning cave lovers) live here. These are animals that like to live inside caves, but can live outside too, like some spiders, cockroaches, crickets, owls, and snails.

* Dark Zone: is home to the troglobites, which are underground creatures that only live in the deepest, darkest parts of caves. They are very small animals. Most are blind or have very tiny eyes. They usually have a white or colorless skin or shell. These include certain types of cave fish, crabs, crayfish, insects, and some salamanders, Only fungi or other plants that do not need sunlight grow here.

Level Pre-A

Main Concepts: Caves are large open areas formed under the ground. Many unusual rock formations can be found in caves.

Picture Activity

Have your students look at the different rock formations pictured in the cave. Explain that caves are made when water washes away parts of rock over many, many years. Caves can have lots of strange and beautiful rock shapes inside them. Introduce the terms stalactite and stalagmite. Say the words out loud together a few times. Stalactites hang down from the top of the cave. Stalagmites are formed on the floor of the cave. (One way to help remember the difference is that stalactite has lots of "t" sounds in it, like the word "top.") Stalactites hang from the "top" of the cave roof.

Vocabulary

First write a large V on the board. Then have everyone say the word cave together, emphasizing the "V" sound. Tell them that we are all going on a cave hunt today with WHY-FLY to look for some hidden letter V's. Tell them to be careful and not to get fooled! They need to find the real V's (with the point facing down). There are other shapes hiding in here, too. Explain that there are many animals that like to live in caves, like bats, bears, snakes, and some insects. (See the Cave Life section in the Background.)

Weekly Lab

You need: (for each child) 1 cup of sand, 1/2 cup of Epsom salts, 1/2 cup of water, a paper towel, a small bowl, a plastic disposable plate, a flashlight. You may need to adjust these amounts, depending on the coarseness of your sand. You will want your mixture to have a fairly thick, oozy consistency. Remind them that stalagmites are formed on the floor of a cave. They build upward. First have them fold their paper towel in half twice and place it on their plastic plate. Make a mixture out of the sand, Epsom salts, and water. Next, have them scoop one handful (at a time) of the mixture and drizzle it from a little above their paper towel. (You may want to demonstrate how to drizzle - letting a little go through their fingers and palms at a time, using a rubbing motion.) With practice, their mixture will build to form and hold a stalagmite shape. Allow their stalagmite sculptures to dry for a while, then have them shine a flashlight on them. The Epsom salt crystals will be visible and "sparkly." Explain that the materials they used are very similar to the ones found in real caves. (This lab can also be done in small groups sharing large bowls of the mixture. Start with approximately 2 lbs. of sand, a 1 lb. container of Epsom salts, and 1 cup of water, adding more water until you achieve the right consistency.)

Weekly Problem

Answers: There are 5 stalagmites and 4 stalactites. Go over the pictures and review that stalactites hang down from the roof of a cave. Stalagmites form on the cave floor and build upward. You may want to explain that stalactites and stalagmites are formed when dripping water in a cave dries up. This water contained tiny, tiny bits of rock in it. When the water dried up - all that was left were the bits of rock. If the water was dripping from the ceiling when it dried up, the bits of rock were left hanging to form a stalactite. If some of the water had dripped down to the cave floor, then the bits of rock formed a stalagmite. It takes thousands of years for a stalagmite or stalactite to form.

Storytelling

Have them look at each picture in the key and ask what they think it means. Next, read the words under each picture and have them repeat these several times. Then play a game by calling out the words in random order and having them point to the correct matching picture. Have them try to "read" the pictures on the cave wall. (I eat fish.) Encourage them to make up (and draw) their own stories with these symbols. As an extension, you can also copy these symbols (and others) onto index cards, then have your students arrange them to make new sentences.

Challenge

Explain that many caves are part of big cave systems that are made up of long series of interconnecting tunnels and caverns that run deep underground. Caves can have many different and unusual rock shapes inside of them. (See Types of Cave Formations in the Background.)

Home Base

This activity can be done at home or in class. Have them make their own caves by cutting out and folding the stalactites and stalagmites. Then have them glue these to the inside of a shoe box that has been painted black (or use a black marker). They can also lightly "paint" their rock formations with a solution of Epsom salts and water. When dried, they can shine a flashlight on them to see their rock formations sparkle, like crystal caves.

Level A

Main Concepts and Picture Activity: See TN Level Pre-A.

Vocabulary

Have them find the rhyming words (bat, rat, cat, hat). Ask if they can think of any other words that also rhyme with these. Next, carefully go over where they are to draw each animal. The cat needs to be outside of the cave, since it is running after the rat (which is going into the cave).

Weekly Lab and Weekly Problem

See TN Level Pre-A - WEEKLY LAB and WEEKLY PROBLEM. In addition, help them fill-in the number sentence using the color-coded boxes. (5 + 4 = 9)

Writing For Science

Have them look at each picture in the key and ask what they think it could mean. Read the words under each picture together. Then play a game by calling out the words in random order and having them point to the correct matching picture. Next, have them write out the message they see on the cave wall. (I eat fish.) Encourage them to write (and draw) their own stories using these symbols. As an extension, you can also copy these symbols (and others) onto index cards, then have your students arrange them to make new sentences.

Challenge

Explain that many caves are part of big cave systems that are made up of long series of interconnecting tunnels and caverns that run deep underground. Caves can have many different and unusual rock shapes inside of them. (See Types of Cave Formations in the Background.)

Home Base

See TN Level Pre-A - HOME BASE. In addition, they may want to add some animals to their caves, like a bat or bear. (See the Cave Life section in the Background.)

Level B

Main Concepts: Caves are large dark areas under the ground. Many unusual rock formations can be found in caves. These formations take thousands of years to form.

Vocabulary

Answers: 1) rock 2) cave 3) roof 4) ground Bonus: under.

Weekly Lab

(Disposable plastic plates work well for this activity.) You may need to adjust the amounts listed, depending on the coarseness of your sand. You will want your mixture to have a fairly thick, oozy consistency. (You may want to demonstrate how to drizzle - letting a little go through their fingers and palms at a time, using a rubbing motion.) With practice, their sand mixture will build to form and hold a stalagmite shape. Allow their stalagmite sculptures to dry for a while, then have them shine a flashlight on them. The Epsom salt crystals will be visible and "sparkly." Explain that the materials they used are very similar to the ones found in real caves. (This lab can also be done in small groups sharing large bowls of the mixture. Start with approximately 2 lbs. of sand, a 1 lb. container of Epsom salts, and 1 cup of water, adding more water until you achieve the right consistency.) Explain that stalagmites are formed when water containing dissolved rock drips onto the cave floor. When the water dries up, all that is left is the rock. Stalagmite and stalactites take thousands of years to form.

Weekly Problem

Answers: a) 15 meters b) 19 meters c) 23 meters. The longest stalactite ever measured was 195 feet long (about 59 meters). That's about the size from the ceiling to the floor of the room they are in - stacked on top of each other 24 times! For your students unfamiliar with metric measurement, explain that it is another way of measuring things instead of using feet and inches. The metric system is used throughout most of the world.

Writing for Science

Have them look at the pictures in the key. Ask what other symbols they could draw for the words: sleep, hunt, hurt, etc. Have them draw these on the board. Next have them write out the message they see on the cave wall. (I eat fish.) Then ask them to write some other "cave picture sentences" of their own and exchange them. Can their friends understand what their picture is meant to say? (Encourage them to invent more symbols of their own for other words.) As an extension, have them write a story about what it would be like to live in a cave.

Challenge

See TN Level A - CHALLENGE.

Home Base

This activity can be done at home or in class. Have them make their own caves by cutting out and folding the stalactites and stalagmites. Then have them glue these to the inside of a shoe box that has been painted black (or use a black marker). They can also lightly "paint" their rock formations with a solution of Epsom salts and water. When dried, they can shine a flashlight on them to see their rock formations sparkle, like crystal caves. They may want to add some animals to their caves, like a bat or bear. (See Cave Life in the Background.)

Level C

Main Concepts: Caves are usually formed in limestone rock, flax, which dissolves easily in flowing water. It takes thousands of years for the many unusual rock shapes in a cave to form.

Vocabulary

Answers: 1) rock 2) cave 3) roof 4) ground 5) form Bonus: under.

Weekly Lab

(Wool yarn or thick cotton string are best for this activity. Acrylic yarns will not work well.) Disposable plastic plates are needed, because paper plates will not hold the dripping liquid. Make sure that the ends of their yam are completely in the liquid of each jar. The yam needs to dip in the center, so it can direct the solution downward. Once the water begins to evaporate, they will see a stalactite and stalagmite forming. If nothing has begun to form after 2-3 days, dip the entire piece of yam into the solution in one of the jars, and try the experiment again.

Weekly Problem

Answers: Tell them to work from left to right. 1) 195 feet (about 60 meters) 2) 200 feet (about 62 meters) 3) 350 miles (about 567 kilometers). Bonus: Tums[R] anti-acid tablets and limestone are made of the same chemical - calcium carbonate. Most caves form in limestone, which dissolves easily in water. Over thousands of years, the water can eat away enough limestone rock to leave a huge hole - a cave.

Writing for Science

Have them really think about all of the things they would need to safely explore a dark, damp cave, including exploring equipment, food, personal items, etc. They can also do this activity in small groups or with partners. Have them compare their lists and explain why they chose particular items. As an extension, have them write about what it was like exploring their cave and what they found.

Challenge

They will be making their own caves by cutting out and folding these stalactites and stalagmites and gluing them inside a shoe box. First have them paint the inside of the shoe box black (or use a black marker). They can also lightly "paint" their rock formations with a solution of Epsom salts and water. When dried, they can shine a flashlight on them to see their rock formations sparkle, like crystal caves. They may want to add some animals to their caves, like a bat or bear. (See the Cave Life section in the Background.)

Level D

Main Concepts: See TN Level C.

Vocabulary

Answer: The temperature in the deepest part of a cave remains the same throughout the year. Each set of arrows points to a box that contains a letter and one that is blank. Explain that when the arrows point to two blank boxes, one of the blank boxes is also part of another set of arrows. One of these boxes must be filled-in first, before they can discover the other one. Some boxes are set-up in a connecting chain.

Weekly Lab

See TN Level C - WEEKLY LAB.

Weekly Problem

Answers: Tell them to work from left to right. 1) 195 feet (about 60 meters) 2) 200 feet (about 62 meters) 3) 350 miles (about 567 kilometers) 4) 5287 feet (about 1602 meters). Tell them to watch out for the (-) sign in Problem 4.

Writing for Science

See TN Level C -- WRITING FOR SCIENCE.

Challenge

Tums[R] anti-acid tablets and limestone are made from the same Chemical -- calcium carbonate. Explain that water picks up carbon dioxide from the air. It also picks up more carbon dioxide from the ground, as it flows down through the earth. When this happens, the water becomes slightly acidic (like the vinegar). The more acidic the water becomes, the more rapidly it will eat away at the limestone. Over thousands of years, the water can eat away enough limestone rock to leave a huge hole - a cave!

Puzzle

See TN Level C - PUZZLE.

Level E

Main Concepts: Caves are usually formed in limestone, when water dissolves large underground areas. Once a cave is formed, water that continues to drip down can form strange and unusual rock formations. These formations take thousands of years to form.

Vocabulary

Answer: The temperature in the deepest part of a cave remains the same throughout the year. Each set of arrows points to a box that contains a letter and one that is blank. Explain that when the arrows point to two blank boxes, one of the blank boxes is also part of another set of arrows. One of these boxes must be filled-in first, before they can discover the other one. Some boxes are set-up in a connecting chain.

Weekly Lab

(Wool yarn or thick cotton string are best. Acrylic yams will not work well for this lab.) Disposable plastic plates are needed, because paper plates will not hold the dripping liquid. Make sure that the ends of their yam are completely in the liquid of each jar. The yam needs to dip in the center, so it can direct the solution downward. Once the water begins to evaporate, they will see a stalactite and stalagmite forming. If nothing has begun to form after 2-3 days, dip the entire piece of yarn into the solution in one of the jars, and try the experiment again.

Weekly Problem

Answers: Tell them to work from left to right. 1) 195 feet (about 60 meters) 2) 200 feet (about 62 meters) 3) 350 miles (about 567 kilometers) 4) 5287 feet (tell them to look carefully at the process signs in this problem) 5) about 1602 meters.

Writing for Science

Have them really think about all of the things they would need to safely explore a dark, damp cave, including exploring equipment, food, personal items, etc. They can also do this activity in small groups or with partners. Have them compare their lists and explain why they chose particular items. As an extension, have them write about what it was like exploring their cave and what they found.

Challenge

See TN Level D - CHALLENGE.

Puzzle

Answers: Dan) 7 - 3 Van) 6 - 5 - 3 Nan) 5 - 2 - 2 - 7 - 3 Fran) 5 - 2 - 7 - 5 - 3. You may want to do a few of these together, or have them work with a partner. Other combinations are possible.

Level F

Main Concepts: See TN Level E.

Weekly Lab

Lab A: See TN Level E - WEEKLY LAB. Lab B: Tums[R] anti-acid tablets and limestone are made from the same chemical - calcium carbonate. Explain that water picks up carbon dioxide from the air. It also picks up more carbon dioxide from the ground, as it flows down through the earth. When this happens, the water becomes slightly acidic (like the vinegar). The more acidic the water becomes, the more rapidly it will eat away at the limestone. Over thousands of years, the water can eat away enough limestone rock to leave a huge hole - a cave!

Weekly Problem

Answers: Tell them to work from left to right. 1) 195 feet (about 60 meters) 2) 200 feet (about 62 meters) 3) 350 miles (about 567 kilometers) 4) 1799 5) 5287 feet (tell them to look carefully at the process signs in this problem) 6) about 1602 meters.

Writing for Science

See TN Level E - WRITING FOR SCIENCE

Challenge

Answer: The temperature in the deepest part of a cave remains the same throughout the year. Each set of arrows points to a box that contains a letter and one that is blank. Explain that when the arrows point to two blank boxes, one of the blank boxes is also part of another set of arrows. One of these boxes must be filled-in first, before they can discover the other one. Some boxes are set-up in a connecting chain.

Puzzle

There are many correct answers to this puzzle. Tell them to watch carefully for the minus signs. They can also do this activity with partners or have a high score competition.

Recommended Resources

* Bendick, Jeanne. Caves! Underground Worlds. New York: Henry Holt and Co., 1995

* Parker, Steve. Science Project Book of the Earth. New York: Marshall Cavendish Corporation, 1993

* Schultz, Ron. Looking Inside Caves and Caverns. Santa Fe, NM: John Muir Publications, 1993

* Silver, Donald M. One Small Square: Cave. New York: W.H. Freeman and Company, 1993

The National Speleological Society, Cave Avenue, Huntsville, AL 35801 (205) 852-1300

Gurnee Guide to American Caves (NCA Books, Route 9, Box 106, McMinnville, TN 37110) lists U.S. caves open to the public.

Materials Needed for Issue 5 - Chemistry

PA, A, B - clear plastic cups, white vinegar, water, baking soda, masking tape, cornstarch, teaspoons, small bowls, plastic plates or pie tins

C - same as above, plus coffee filters, cotton balls (or eye droppers), black water-based markers

D - same as above, plus club soda (optional - different colored water-based markers)

E, F - red cabbage leaves, warm water, zip-type plastic bags, white styrofoam egg cartons (or white plastic ice cubes trays or white disposable cups), white vinegar, baking soda, lemon juice, saltwater, anti-acid tablets, masking tape, clear plastic cups, cornstarch, teaspoons, small bowls, plastic plates or pie tins, club soda, eye droppers
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Copyright 1997 Gale, Cengage Learning. All rights reserved.

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Date:Oct 16, 1997
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