![](media/image1.png){width="0.5834645669291338in"
height="0.75in"}Caves, Canyons, Cactus & Critters

*Middle School Geology*

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height="7.227777777777778in"}

Caves, Canyons, Cactus & Critters

Geology Curriculum

# Oil Munchers Activities exploring the role of anaerobic bacteria in the formation of caves in Carlsbad Caverns National Park. 39

1.  **It's More Than Just Dead Dinosaurs** An activity designed\
    to model oil and gas formation and traps. 40

2.  **Strange Things in Strange Places** An activity to explore\
    bacteria that live in strange places (underground anaerobes,\
    Lechuguilla Cave, thermal springs, Mars) 45

3.  **Stinky Gas and Alabaster** An activity to demonstrate gypsum\
    replacement of limestone in the formation of the caves\
    of the Guadalupes. 48

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**Oil Munchers**

Caves form by many different methods. The caves of the Guadalupe
Mountains, including the caves of Carlsbad Caverns National Park, were
formed by one of the more unusual processes. The formation of the caves
is tied very closely to the hydrocarbon deposits of the Delaware Basin,
found at the base of the Guadalupe Escarpment.

Massive deposits of gypsum have been found in many of the caves of the
Guadalupe Mountains. For many years, geologists attempted to develop
models explaining these deposits, but had little success. It is only in
the past 20-30 years that a model has been proposed that not only
explains the gypsum deposits, but also explains the unique morphology of
the caves. In this model, anaerobic bacteria deep underground in the
Delaware Basin facilitate a reaction between hydrocarbons and calcium
sulfate, or anhydrite. Anhydrite is an anhydrous form of gypsum, which
has water included in its crystalline structure.

According to the model, a byproduct of this reaction, hydrogen sulfide
gas, rose through cracks in the rocks to the top of the water table in
the Guadalupe Mountains. There, oxygen combined with the hydrogen
sulfide gas to produce sulfuric acid. This sulfuric acid reacted with
the limestone rock of the ancient reef and began to dissolve vast
caverns. As the hydrogen sulfide was oxidized deeper and deeper in the
cracks, the deep pits of the caves formed. When groundwater levels
changed, the passages formed at new levels. One byproduct of the
reaction of sulfuric acid and limestone (primarily calcium carbonate)
was calcium sulfate, or gypsum, which was subsequently deposited in the
great voids.

In this unit, students will engage in activities designed to help
introduce various components of Guadalupe Mountain speleogenesis. Very
complex chemical reactions and processes have been simplified in these
activities. If students are interested in learning more, recommend that
they read the book *Stories From Stones: The Geology of the Guadalupe
Mountains.* Also, recommend that they take chemistry as part of their
high school course work.

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**It's More Than Just Dead Dinosaurs!**

***How does oil and gas form and why does it collect in one place
underground?***

**Summary:** Students will describe how oil and gas form and how they
are trapped underground.

**Duration:** Three or four 50-minute class periods

**Setting:** Classroom or lab

**Vocabulary:** hydrocarbons, kerogen, permeable, petroleum, petroleum
trap, porosity

**Standards/Benchmarks Addressed:** SC5-E2, SC6-E1, SC12-E1, SC12-E2,
SC12-E5

**Objectives**

Students will:

-   describe how oil and gas form.

-   describe three types of oil and gas traps.

**Background**

![](media/image4.wmf){width="1.2645833333333334in"
height="1.2451388888888888in"}Life, as we know it, would not be
possible, without fossil fuels. The most important of these fuels is
*petroleum.* Another word commonly used in reference to petroleum is
*hydrocarbons.* Molecules of petroleum consist mainly of the elements
hydrogen and carbon. Most petroleum deposits are found in rocks formed
in marine environments.

The formation of petroleum begins in marine basins where microscopic
organisms and algae live suspended in the water. As they die, they sink
to the bottom where they become mixed in with the mud at the bottom of
the basin. The low oxygen environment in the bottom water keeps the
organisms from oxidizing, or decaying. As the sediments continue to
accumulate, the layer bearing the remains of the microscopic organisms
is buried deeper and deeper. Eventually, heat and pressure build to the
point that the remains of the organisms begin to undergo chemical
changes. First, the remains are converted into a waxy hydrocarbon called
*kerogen.* Further heat and pressure causes the kerogen to convert to
the various forms of petroleum with which you are familiar: methane or
natural gas, oil, gasoline, kerosene, and diesel oil. The rocks these
hydrocarbons come from are called source rocks*.*

Within the petroleum reservoir, the various hydrocarbons begin to sort
themselves based on density and to migrate through rocks with pathways
formed by cracks, spaces between grains, or pores in the rocks. These
openings are referred to as *porosity*. If the areas of porosity are
connected and fluid can move through them, the rocks are said to be
permeable. The hydrocarbons will migrate along a bed with *permeability*
until they reach the surface, or reach some geologic structure that
traps them in place. The permeable rock in which the petroleum is
eventually stored is referred to as a reservoir rock*.* Within the
reservoir, the gaseous hydrocarbons, being less dense, move to the top.
Typically, there is water associated with hydrocarbon reservoirs. Since
the water is denser, it is found on the bottom. The liquid hydrocarbons,
or oil, are found in the middle.

The structures, or *petroleum traps,* that stop or slow hydrocarbon
migration can take several forms. Four of the more common traps are
structural traps, stratigraphic traps, salt domes, and reefs. In the
case of a structural trap, features such as faults or folds trap the oil
and gas against an impermeable layer. In stratigraphic traps, reservoirs
are created by differences in the sedimentary layers. Often a permeable
sandstone layer will be "trapped" between two impermeable shale layers.
If these layers are tilted, the hydrocarbons will rise through the
sandstone layer. If this layer thins and eventually pinches out, it will
trap the hydrocarbons, producing a petroleum reservoir. In the case of a
salt dome, a bed of salt "blisters" and shifts upward through the more
dense layers that overlie it. In doing this, it raises part of the
overlying layers, including potential reservoir rocks. Salt is
impermeable, so any hydrocarbons moving along a permeable layer will
become trapped in the reservoir. Due to the nature of the organisms that
form it, a *reef* becomes a very porous and permeable bed of limestone.
If the reef lies near source rocks and is capped by an impermeable
layer, it becomes an excellent reservoir rock.

In the Delaware Basin, the hydrocarbons are thought to be of marine
origin, resulting from the remains of microscopic organisms that lived
in the ancient seas. Within the basin today, most of the petroleum that
is found is located in stratigraphic traps. The Capitan Reef certainly
meets the requirement of being porous. The caves of the Carlsbad Caverns
National Park are just an example of the great porosity to be found in
the ancient reef. But current research seems to indicate that no
hydrocarbons ever migrated into, or through, the great reef. There is,
however, evidence of hydrocarbon migration under the reef from the basin
to the southeast, to the backreef, northwest of the park. Why the
hydrocarbons did not enter the reef is still a source of speculation and
research for geologists from around the world.

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**Materials**

-   graduated 250 ml beakers -- 3

-   100 ml beakers -- 3

-   several 2 or 3-liter soda bottles

-   oil (can be cooking oil or motor oil)

-   sand (several colors, if possible)

-   gravel (several colors, if possible)

-   scoria (holy lava rock, batman!)

-   clay

**Procedure**

***Warm up:*** Ask students how oil and gas form. Most students will
respond that it forms from dead dinosaurs. Discuss with the students the
need for a low oxygen environment if oil and gas are to form from an
organism and how most dinosaurs were not in a position to be preserved.

Ask students if much lives in the oceans. Guide the discussion to the
topic of microscopic organisms, such as algae, diatoms, and plankton.
Ask the students what happens to those organisms when they die. Discuss
and describe how these microscopic organisms, small as they are, "pile
up" on the ocean floor where the low oxygen environment allows them to
be buried and slowly converted into hydrocarbons. If any student doubts
that this is possible, you might want to review with the class the diet
of the world's largest mammal, the blue whale, which feeds on these very
microscopic organisms.

Discuss and describe with the students how these microorganisms are,
with time, pressure, and heat converted into hydrocarbons.

***Activity***

1.  Prepare bottles to demonstrate porosity and permeability as follows:

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a.  Cut the bottom 3 or 4 inches from three 3-liter bottles and turn
    them over.

b.  Glue a single layer of cloth into the bottom of each to keep the
    sand and gravel from coming out.

c.  Fill the bottles as shown

    2.  Turn all three bottles upside-down with a graduated 250 ml
        beaker under each. Ask the students, "If I pour 100 ml of water
        into each of these at the same time, which will it travel
        through fastest?" Be open to all suggestions. Have the students
        justify their guesses. Have students assist you and pour 100 ml
        into each bottle at the same time. Monitor the 250 ml beakers to
        see which bottle the water passes through fastest. Discuss the
        results with the class. Solicit their hypotheses regarding the
        different rates of infiltration through the bottles.

    3.  Define porosity for the students. Show students a piece of
        scoria (lava rock with holes in it), a piece of sandstone, and a
        piece of conglomerate or a handful of gravel. Ask which of the
        samples exhibit porosity. Students should answer "all three" Ask
        which would form a rock through which fluids would move the
        easiest. Some students may select the scoria, due to the size of
        the pores. Point out to students that even though all three
        samples have porosity, the holes are not connected in the
        scoria, so fluid would not move through it as easily. The pores
        in the gravel are bigger than the pores in the sand or
        sandstone, so fluid would move through the gravel easier.
        Discuss the differences in porosity and permeability. Expand
        discussion to point out that water is not the only fluid that
        moves through the ground, oil and gas also migrate.

    4.  Ask the students what happens when you mix oil and water. Mix
        100 ml water with 10 ml oil and have students observe and
        describe the results. Ask them why the oil rests on the top of
        the water. If necessary, review the concept of *density* and why
        some objects float on others. Ask the students what would happen
        in a permeable layer of rock if water, oil, and natural gas were
        mixed. Discussion should lead to the idea that they would
        separate with the gas on top and the water on the bottom.

    5.  Ask the students, "If the hydrocarbons are moving through the
        ground in a permeable layer of rock, what could stop them?"
        Entertain all suggestions. Describe the concept of *petroleum
        traps* to the students. Using overhead or board drawings,
        demonstrate and discuss stratigraphic, structural, salt dome,
        and reef traps.

    6.  Cut the bottom off empty 3 liter soda bottles approximately 5
        inches from the bottom. Leaving the cap tightly secured, turn
        empty 3-liter soda bottles over and place the top into the
        bottom, using the bottom as a stand. In the bottle, have each
        group use sand, gravel, clay, or other materials you have
        provided to construct a model of one of the petroleum traps you
        have assigned them. With several colors of materials, you can
        have the students be very creative in their models.

***Wrap Up:*** Display the models in view of all students. Using the
models in your discussion, briefly review the concepts of porosity,
permeability, and the various types of petroleum traps. Ask the students
to critique the strong and weak points of using the 3-liter bottle
models to discuss these concepts.

**Assessment**

Have students:

-   List three things this lesson taught them that they didn't already
    know or that they learned more about as a result of the lesson.

-   Describe how oil and gas are formed.

-   Define and describe permeability and porosity.

-   Describe three types of petroleum traps.

**Extensions**

Have a guest speaker involved in the oil and gas industry speak on oil
and gas exploration and how wells are drilled.

Have students research society's dependence on petroleum. Have them
include alternative energy sources in their research.

**Resources**

Chernicoff, S., Fos, H.A., and Venkatakrishnan, R. 1997. *Essentials of
Geology.* New York, NY: Worth Publishers.

Hill, Carol. 1996. *Geology of the Delaware Basin, Guadalupe, Apache,
and Glass Mountains, New Mexico and West Texas:* Permian Basin Section
SEPM, Publication No. 96-39.

Murck, B.W., Skinner, B.J., and Porter, S.C. 1996. *Environmental
Geology.* New York, NY: John Wiley & Sons, Inc.

Shew, R.D. 1998. *Geology of the Guadalupe Mountains.* Guidebook
prepared for field seminar/workshop conducted by Guadalupe Mountains
National Park and New Mexico State University-Carlsbad.

Shew, R.D., and Shew, D.M. 2000. *Geology and Natural History of
McKittrick Canyon.* Guidebook prepared for workshop conducted by
Guadalupe Mountains National Park and New Mexico State
University-Carlsbad.

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**Strange Things in Strange Places**

***Just how extreme an environment can some things live in?***

**Summary:** Students will use information learned in class discussion
to play a game in which they describe several environments in which
bacteria are found.

**Duration:** One or two 50-minute class periods

**Setting:** Classroom

**Vocabulary:** anaerobic bacteria, corrosion residues, extremophile,
moonmilk, pool fingers

**Standards/Benchmarks Addressed:** SC1-E2, SC12-E7

**Objectives**

Students will:

-   describe three "hostile" environments in which bacteria are found.

**Background**

![](media/image10.wmf){width="0.9895833333333334in"
height="1.2916666666666667in"}When we think of the environments in which
organisms live, we tend to think of our own comfort zone. When asked to
think of organisms that live in extreme environments, most people will
think of polar bears, camels, or birds. Cold weather, hot and dry, or
high above the earth are as extreme an environment as most people can
imagine for living organisms. However, research has shown that some
microorganisms can live in environments far more extreme than was once
thought possible.

Microorganisms have been found living in some very hostile environments.
Among these are the cold of the Arctic and Antarctic, volcanic vents,
hot vents on the ocean floor, in very dry locations, in rocks deep in
the earth, in severe chemical environments, in hot springs, and in
high-radiation environments. These *extremophiles* were not really
recognized until the 1970s, but after their discovery were found to be
located in the harshest environments on earth.

Throughout the course of their evolution, these organisms developed
traits that enabled them to live in their particular, peculiar
environments. Those living in freezing temperatures have, as part of
their cellular composition, anti-freeze compounds, such as salts,
sugars, and amino acids. Thermophiles, those organisms that thrive in
excessive heat, are found in the hot springs of Yellowstone National
Park and deep in the middle of the Atlantic Ocean, near black smokers,
vents that spew superheated water. Those living in extreme chemical
environments have developed body processes that enable them to deal with
excessively acidic, alkaline, or salty environments.

Extremophiles have also been found deep underground. Some of these
extremophiles actually live in the rock. They are anaerobic and do not
require oxygen to respire. Some of these feed off hydrogen gas released
when groundwater reacts with the rocks through which it is passing. In
the Delaware Basin, anaerobic bacteria obtained the energy to live by
facilitating the redox reactions of sulfur contained in gypsum and
carbon contained in methane. At the boundary of the Castile Formation
(impermeable gypsum) and the underlying Delaware Mountain Group
(permeable oil and gas bearing beds), bacteria facilitated the following
reaction:

Ca^2+^+2SO~4~^-2^+2CH~4~+2H^+^=2H~2~S+CaCO~3~+3H~2~O+CO~2~

In this reaction, the sulfur in anhydrite (CaSO~4~) was reduced and
combined with the acidic hydrogen (H^+^) to produce hydrogen sulfide
(H~2~S). The carbon contained in methane (CH~4~) was oxidized to produce
a carbonate ion (CO~3~^-2^) that combined with the available calcium ion
(Ca^2^) to produce limestone (CaCO~3~). This limestone often carries the
structures and bedding seen in gypsum next to it, so it is believed that
this alteration from gypsum to limestone occurred in-situ. The hydrogen
sulfide then moved through cracks into the reef where, near the water
table, it was oxidized to form sulfuric acid (H~2~SO~4~). This acid
dissolved the great voids that became the caves of the Guadalupe
Mountains. A byproduct of this reaction occurred when the sulfate ion
(SO~4~^-2^) combined with calcium ions (Ca^+2^) released in the reaction
and water to form gypsum (CaSO~4~ 2H~2~O).

In the caves of Carlsbad Caverns National Park, an abundance of evidence
has been obtained that indicates microbes are responsible for many of
the more unusual features seen. Among those unusual features are
*corrosion residues*, a material composed mostly of insoluble residues.
Research has indicated that these residues are the offal of the bacteria
that have eaten the bedrock. In the areas where this residue is found,
it coats the floors and walls of the cave. *Pool fingers* are slender
calcite fingers, up to 30 cm long and around 2 to 6 mm in diameter.
These fingers formed below the water level in pools and contained what
have been interpreted to be bacterial filaments. *Moonmilk* is a pasty
material consisting of calcite, hydromagnesite, gypsum, or other
materials. It occurs in limited deposits in the caves of the Guadalupe
Mountains. When studied at high magnification, it appears to contain
filaments or fibers that may be bacterial in origin. Much of this
research has been conducted in Lechuguilla Cave.

Microbiologists continue to study the life in the caves of Carlsbad
Caverns National Park. While the entrance area of Lechuguilla Cave was
mined for many years, the first know entry of humans into the depths did
not occur 1986. That year, a group of cave explorers from Colorado,
following air blowing through a pile of rock and dirt on the floor dug
into a passage leading to the depths of the cave. As soon as the park
realized what a unique resource the cave was, restrictions were placed
on exploration and research in the cave to help preserve its unique
environment. Numerous new bacteria have been found in the cave. Dr. L.M.
Mallory and others have been very active in studying these bacteria and
their possible help in creating a cure for cancer and other illnesses.
NASA has shown a great interest in the microbes of Lechuguilla Cave.
Exobiologists theorize that any life found on other planets in our solar
system will be microbial, similar to that in Lechuguilla Cave. They hope
that studying those organisms will show them the "fingerprint" of any
potential aliens.

**Materials**

-   markers or crayons

-   large (2\' x 3\') sheets of paper

**Procedure**

***Warm up:*** Ask the students "What criteria are essential for
something to live?"

Have the students name the most extreme environments they can think of
where something could still live.

Discuss with the class the various hostile environments on earth in
which microbes live. Remind them that a form of *e. coli* bacteria lives
in their gastrointestinal tract.

Discuss the role bacteria have played in the development of the caves of
Carlsbad Caverns National Park.

***Activity***

1.  Give the students one large (2\' x 3\') of paper and crayons or
    markers.

2.  Tell the students that they are going to design an organism that can
    live in an extreme environment. Give them several examples of
    extreme environments to choose from. Tell them that they must
    explain how their organism adapts to the particular challenges of
    its environment.

3.  Have each group present their work to the class and open the floor
    for questions for each group.

***Wrap Up:*** Ask the students what this lesson has to do with space
travel.

Lead in a discussion about how the environments of other bodies in the
solar system, such as Mars, Io, Ganymede and Europa, may harbor the same
environment in which one of these organisms could live.

**Assessment**

Have students:

-   describe three ways that microbes have adapted to hostile
    environments.

-   briefly, describe the role microbes have played in the development
    of the caves of the Guadalupe Mountains.

-   explain why NASA is interested in the microbes found in Carlsbad
    Caverns National Park caves.

**Extensions**

Using the internet, have students locate NASA related websites
describing the search for extraterrestrial life. Have students study and
report on a potential trip to Jupiter's moon, Europa, or on the search
for life beneath the surface of Mars.

**Resources**

DuChene, H.R., and Hill, C.A. 2000. *The Caves of the Guadalupe
Mountains Research Symposium*. In Hose, L.D. (ed.) *Journal of Cave and
Karst Studies* 62(2).

Hill, C.A. 1987. *Geology of Carlsbad Cavern and Other Caves in the
Guadalupe Mountains, New Mexico and Texas*. Socorro, NM: New Mexico
Bureau of Mines and Mineral Resources, Bulletin 117.

Hill, Carol. 1996. *Geology of the Delaware Basin, Guadalupe, Apache,
and Glass Mountains, New Mexico and West Texas:* Permian Basin Section
SEPM, Publication No. 96-39.

Jagnow, David and Jagnow, Rebecca. 1992. *Stories from Stones: The
Geology of the Guadalupe Mountains.* Carlsbad, NM: Carlsbad Caverns
Guadalupe Mountains Association.

Sasowsky, I.D. and Palmer, M.V. 1994. *Breakthroughs in Karst
Geomicrobiology and Redox Geochemistry.* Karst Waters Institute, Special
Publication 1.

Smith, R.B. and Siegel, L.J. 2000. *Windows Into the Earth.* New York,
NY: Oxford University Press.

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**Stinky Gas and Alabaster**

***How did all that gypsum get into the caves of Carlsbad Caverns
National Park?***

**Summary:** After class discussion, students will engage in a card game
designed to demonstrate the processes leading to the alteration of
limestone to gypsum in the caves of Carlsbad Caverns National Park.

**Duration:** One to two 50-minute class periods

**Setting:** Classroom

**Vocabulary:** dissolve, escarpment, joint, lava tube

**Standards/Benchmarks Addressed:** SC2-E1, SC12-E1, SC12-E7

**Objectives**

Students will:

-   describe the relationship of cave openings in limestone and the
    gypsum deposits found in them.

![](media/image11.wmf){width="1.43125in" height="1.025in"}**Background**

Caves form through many different processes. The classic model for the
formation of solution caves states that mildly acidic meteoric water
*dissolves* bedrock as it descends through it. As the bedrock dissolves,
the widened cracks, or joints, become cave passages. Some of these
widened passages may eventually contain large underground rivers, as is
the case in Mammoth Cave National Park in Kentucky. Similar processes
account for cave formation in gypsum. In the Parks Ranch Cave System in
southeastern New Mexico, approximately 10 km southeast of the Carlsbad
Caverns National Park, infrequent cloudbursts can fill gypsum cave
passages to the ceiling. These caves are often called "desert storm
drains."

On shield volcanoes, such as the extinct volcanoes in El Malpais
National Monument, cave passages are found in the old lava flows. During
the last eruption in this area, fast moving lava cooled and solidified
near the surface while the hot, liquid lava continued to flow inside.
Eventually, the lava flowed out of the tube in places, leaving behind an
opening, or a cave.

Near the edge of mountain *escarpments* where faulting has occurred,
tectonic caves are found. These caves are formed as a fault or a *joint*
widens along the edge of an escarpment rather that being formed by
dissolved bedrock. Several of these caves are found along the Algerita
Escarpment, in the Guadalupe Mountains west and northwest of Carlsbad
Caverns National Park. These caves are often deep shafts lined with a
great deal of loose rock.

Glaciers often have caves along their base. As the ice of the glacier
melts, water will work its way to the base of the glacier where it flows
along the ice/bedrock boundary. There, it can melt a passage large
enough for human to traverse. These glacier caves sometimes go several
hundred feet under a glacier.

The caves of Carlsbad Caverns National Park have a different story. They
were formed by acidic groundwater. However, this water did not descend
from above. Rather, the necessary components actually rose from the
nearby Delaware Basin. In the Delaware Basin, the Castile Formation,
composed primarily of anhydrite or gypsum, overlays the sands,
limestone, and shale of the oil and gas producing Delaware Mountain
Group. Methane gas, moving through the rocks of the Delaware, was
stopped on reaching the impermeable Castile. At that point, anaerobic
bacteria living in the rock facilitated the redox reactions in which the
sulfur contained in anhydrite was altered to become hydrogen sulfide gas
and the carbon contained in the methane gas became part of a calcium
carbonate rock, limestone. Hydrogen sulfide gas is easily identified by
its strong, rotten egg odor. The methane gas produced from the Delaware
Basin is, for the most part, considered to be "sour gas" due to the
amount of hydrogen sulfide it contains. The reaction is summarized in
the following formula:

Ca^2+^+2SO~4~^-2^+2CH~4~+2H^+^=2H~2~S+CaCO~3~+3H~2~O+CO~2~

In this reaction, the sulfur in anhydrite (CaSO~4~) was reduced and
combined with the acidic hydrogen (H^+^) to produce hydrogen sulfide
(H~2~S). The carbon contained in methane (CH~4~) was oxidized to produce
a carbonate ion (CO~3~^-2^) that combined with the available calcium ion
(Ca^2^) to produce limestone (CaCO~3~). This limestone often carries the
structures and bedding seen in gypsum next to it, so it is believed that
this alteration from gypsum to limestone occurred in place.

The hydrogen sulfide then moved through cracks, or joints, into the reef
where it began to migrate upward. Near the water table, it encountered
oxygenated water and was oxidized to form sulfuric acid (H~2~SO~4~).
This acid dissolved the great voids that became the caves of the
Guadalupe Mountains. The joints along which the hydrogen sulfide gas
rose were gradually widened until they became the deep pits that
characterize many caves of the Guadalupe Mountains. The Bottomless Pit
in Carlsbad Cavern is an example of such a pit.

A byproduct of this reaction occurred when the sulfate ion (SO~4~^-2^)
combined with calcium ions (Ca^+2^) released in the reaction and water
to form gypsum (CaSO~4~ 2H~2~O). In Carlsbad Cavern, some of these
massive gypsum deposits can be found in the Big Room near the Jumping
Off Place, the Talcum Passage, and in the New Mexico room. In some caves
of the Carlsbad Caverns National Park, such as Lechuguilla Cave, sulfur
has been deposited in its native yellow crystalline state.

**Materials**

-   Copies of the cards printed at the end of the lesson (glued to
    cardboard and laminated). You will need one set of cards for each
    group of three to four students. Number of each card per set:
    Methane and gypsum (15); Bacteria (5); H~2~S Gas and calcite
    replacing Anhydrite (10); Oxygen + H~2~S = Sulfuric Acid (15);
    Dissolves limestone and deposits gypsum (10).

**Procedure**

***Warm up:*** Ask the class how caves form. Write all ideas on an
overhead or board. Discuss the various ideas presented.

Describe and discuss with the class the current model of how the caves
of the Guadalupe Mountains formed.

***Activity***

1.  The objective of the game is to be the first to obtain a complete
    set of five cards and lay them down *in order* (Methane and Gypsum,
    Anaerobic Bacteria, H~2~S Gas, Sulfuric Acid, Deposits Gypsum).
    Provide each group of three or four students with a complete set of
    game cards. Tell students to shuffle the cards and leave them face
    down.

2.  Tell the students to deal each person in the group a hand of five
    cards and to look at their own hand, but not to show anyone else.

3.  Tell the dealer to place the remainder of the stack face down on the
    table. This becomes the "draw pile." Tell them to then turn over the
    first card on the deck, placing it on the table next to the draw
    deck. This will start the "discard pile."

4.  The person to the dealer's left will be the first to go. They have a
    choice of picking up the top card on the "draw pile" or the top card
    on the "discard pile." In selecting, they should remember that they
    are trying to be the first to get a complete set of five cards.

5.  After drawing, that player must select a card from their hand to
    discard. He/she places that card, face up, on the discard pile. Play
    then moves to the next person who also chooses between the unknown,
    face down card on the "draw pile" or the known, face up card on the
    "discard pile."

6.  The game continues until one player has a complete set of five
    cards. They MUST lay the cards down in the proper order. It is the
    responsibility of the other group members to see that this is done
    correctly.

7.  Play can continue through one hand or through several, depending on
    what time allows.

***Wrap Up:*** Hold up game cards, one at a time, and have students tell
which step comes next.

Ask the students to again describe the ways in which caves can form. Ask
if they had ever considered that bacteria could be responsible for the
formation of a cave like Carlsbad Cavern.

**Assessment**

Have students:

-   describe three different ways in which caves form.

-   describe the role of bacteria in the formation of Carlsbad Cavern.

-   explain how calcium in the limestone of the Capitan Reef can be
    altered to become part of large gypsum deposits in caves.

**Extensions**

Have students conduct internet and library research on other caves with
unusual stories. Examples of possible caves to study are Cueva de Villa
Luz in Tabasco, Mexico where slimy bacterial formations hang from the
ceiling over acidic water. These slimy formations have been given the
name "snottites." This activity does not need to focus on bacterial
activity in caves. Rather, the students should look for facts that they
find to be interesting and unusual.

**Resources**

DuChene, H.R., and Hill, C.A. 2000. *The Caves of the Guadalupe
Mountains Research Symposium*. In Hose, L.D. (ed.) *Journal of Cave and
Karst Studies* 62(2).

Hill, C.A. 1987. *Geology of Carlsbad Cavern and Other Caves in the
Guadalupe Mountains, New Mexico and Texas*. Socorro, NM: New Mexico
Bureau of Mines and Mineral Resources, Bulletin 117.

Jagnow, David and Jagnow, Rebecca. 1992. *Stories from Stones: The
Geology of the Guadalupe Mountains.* Carlsbad, NM: Carlsbad Caverns
Guadalupe Mountains Association.

**Stinky Gas and Alabaster**

**Materials**

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