![](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

# Surf Carlsbad! Activities related to the development of the Delaware Basin and Capitan Reef. 5

1.  **A House Made of Sponge?** Game introducing the\
    various organisms believed to have formed the Capitan Reef. 6

2.  **Old Salts** Activity designed to demonstrate the\
    precipitation and sedimentation of salts in the Delaware Basin. 11

3.  **Is it Limestone, or Did I Get Gyped?** Activity to introduce the\
    main Permian Age rocks found in the Carlsbad Caverns National\
    Park Area and the minerals they are made of; limestone,\
    gypsum, halite, sandstone, shale. (A very basic mineralogy\
    and petrology lab.) 14

4.  **Meet My Pet Fossil, Rocky** Activity in which students make\
    plaster-of-Paris fossils and then study a real fossil; describing
    it,\
    its environment, what and how it ate, etc. 19

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**Surf Carlsbad!**

As hard as it may be to believe, the southeastern corner of New Mexico
was once a shallow inland sea; home to a fascinating barrier reef that
is exposed today in the Guadalupe Mountains where Carlsbad Caverns
National Park is located. The growth of this reef, as well as the
development of thick basin deposits and a series of backreef deposits,
has resulted in a world-class geologic classroom. Geologists from around
the world come to the Carlsbad Caverns National Park to study
backreef-reef-basin sequences, carbonate shelf formation, evaporite
basins, and the fascinating caves that form in these soluble rocks.

This unit will focus on the rocks formed in this ancient reef
environment. In the first activity, students will study the main
reef-forming organisms found in the Capitan Reef. The second activity
will provide students the opportunity to study the development of the
thick salt deposits found in the Delaware Basin. In the third activity,
students will learn to identify the main sedimentary rocks found in
Carlsbad Caverns National Park. The last activity will give students the
opportunity to explore ancient life through fossils.

The background for these activities is closely tied to the book
***Stories From Stones: The Geology of the Guadalupe Mountains***. It is
strongly recommended that you read this book or have a working knowledge
of the geology of the Guadalupe Mountains prior to teaching this unit.

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**A House Made of\... Sponge?**

***What types of organisms would you have seen if you had\
visited the Permian Reef when it was forming?***

**Summary:** Students will discuss organisms that formed the Permian
Reef and will then participate in a game where they are required to
recall the information learned.

**Duration:** 50-minute class period

**Setting:** Classroom

**Vocabulary:** calcareous, reef, extinction, Pangea

**Standards/Benchmarks Addressed:** SC11-E5, SC12-E5

**Objectives**

Students will:

-   name and describe several organisms responsible for forming the
    Permian Reef.

![](media/image4.png){width="1.3020833333333333in"
height="1.3125in"}**Background**

During the late Permian Period (280-225 million years ago) North America
was a part of the super continent *Pangea*. Carlsbad Caverns National
Park was located very close to the equator. A shallow inland ocean
covered southeastern New Mexico and the area known as the "Permian
Basin." The Hovey Channel to the south-southwest connected this ocean to
the larger Permian Ocean. Conditions in the western part of the basin,
an area that is called the "Delaware Basin" today, were favorable to the
development and growth of many of the organisms living in the ancient
ocean. Included in those organisms were a variety of shellfish,
fusilinids, algae, echinoderms, trilobites, corals, and colonial
organisms such as sponges and bryozoans.

Among the shellfish were organisms such as pelecypods and brachiopods.
The shells of these organisms were calcareous, consisting of calcium
carbonate (CaCO~3~). Pelecypods are classified as bivalves and are
identified by their hinged, two-halved shell in which the halves are
usually symmetrical or the same. Scallops would be an example of modern
day bivalves. Brachiopods were similar, but the two-halves of their
shells are not symmetrical. They are sometimes referred to as "flying"
shellfish due to the "wing-like" appearance of their shells. While
brachiopods lived primarily on the reef, pelecypods are believed to have
lived more along the reef/backreef boundary, closer to the lagoon area.
Both fed by filtering food particles suspended in the water.

Another group of shellfish found in the Permian Sea was the gastropods.
Gastropods would be most familiar to us as the common snail. They are
recognized by their coiled shell and the way they move about on a wide,
flat foot. A gastropod's primary source of food was algae.

Though they are thought of as the major reef-builders in modern oceans,
corals were rare in the Permian Sea. Many of those found are solitary
horn corals. Instead, algae were one of the primary reef-building
organisms found in the Permian Sea. Several varieties of *calcareous*
algae were present in the *reef* area and contributed greatly to the
growth of the reef. The other major reef builders were sponges. Sponges
were colony creatures forming a calcareous house in which they would
live and filter food from the water. Several species of sponge have been
found in many shapes and forms.

Bryozoans were another type of colonial organism that lived in the
Permian Sea. Bryozoans formed colonies resembling delicate fans along
the ocean floor. Like many other organisms along the reef, bryozoans
also filtered their food from the water.

Echinoderms were also present. They are easily identified by their five
"ray" or five-part symmetry. An echinoderm frequently found among
fossils in the reef is the crinoid, a flowerlike organism that filtered
food particles suspended in the water.

Many people think of the extinction of the dinosaurs as the greatest
*extinction* of all time. However, it pales in comparison to the mass
extinction that occurred at the end of the Permian Period. By some
estimates, nearly ninety percent of the species on Earth at that time
became extinct.

**Materials**

-   One set of ***Reef Builders*** cards per group of students
    (pre-mounting on cardboard will make the cards more durable)

-   Paper for notes during warm-up

-   Paper for keeping score

**Procedure**

***Warm Up:*** Inform students that the information you are about to
discuss will be very useful later in the lesson. Suggest that they write
down the names and characteristics of the organisms you will be
discussing while you write difficult to spell words on the board.

Discuss reefs, how they are formed from the calcareous remains of living
organisms, how they form in tropical environments along shallow ocean
areas, etc. Use modern-day reefs such as the Great Barrier Reef in
Australia or the reefs of Belize as examples in your discussions.

Describe and discuss the organisms responsible for building reefs today.
Compare and contrast those to the reef-builders of the Permian Period.
Be sure to focus on the environments in which they live, how their
shells are formed, and how they feed.

Ask students to list the characteristics found off the coast of
Australia or Belize that make ideal environments for reef-building
organisms (warm tropical water, shallow water allowing more light, well
oxygenated water, etc.). Ask students if they believe conditions near
Carlsbad, New Mexico, were different during the Permian Period. Ask them
to describe what they think the area near Carlsbad Caverns National Park
would have been like 230 million years ago.

***Activity***

1.  Tell students that they are going to use their knowledge of
    reef-building organisms from the Permian Period in a game. Have
    students form into groups of three or four.

2.  Hand out the Reef Builder cards, face down, to each group of
    students and instruct them to not look at the cards before being
    told to do so.

3.  Explain that each card lists four characteristics of a reef-building
    organism from the Permian Period. They will try to guess what the
    organism is while being given the clues.

4.  The person initially given the cards will read the clues, one at a
    time in order, until someone in the group guesses the organism or
    until all clues are used without a successful guess.

5.  Students begin to read the clues while others in the group attempt
    to guess the name of the organism. Points are given for successful
    answers as shown below. The student who successfully answers will be
    the reader for the next card.

    -   One clue - 4 points

    -   Two clues - 3 points

    -   Three clues - 2 points

    -   Four clues - 1 point

6.  The game continues until all of the cards have been read. For those
    students with the highest score, or who score more than a
    pre-determined number of points, provide a prize or reward.

***Wrap Up:*** Discuss what might happen to the reef if any of the
environmental conditions changed (change in water temperature, sea
level, available oxygen, etc.). Have students theorize about what might
have brought about the eventual end of growth on the Permian Reef.

Discuss current reefs and any conditions that may be threatening their
growth (ocean warming, sea level changes, other organisms that feed on
reef builders, etc.). Have students describe how studying ancient
environments, such as the Permian Reef, can help us better understand
our Earth today.

**Assessment**

Have students:

-   name an organism when given a set of its characteristics.

-   explain what characteristics make an area of the ocean favorable for
    reef growth.

-   describe why the study of fossils can help us make informed
    decisions about our Earth today.

**Extension**

Working in a group of three or four, students select an ecosystem from a
given list (desert, rain forest, mountains, etc.). Have them discuss
within their group the types of organisms, plants and animals, which
would be typical for that ecosystem. They should list the organisms, as
well as characteristics we would use to identify that organism.

They will then move forward into the future 230 million years and
describe what a person studying fossils from their ecosystem might find.
They should also try to predict any misconceptions a future
paleontologist might have from misinterpreting the fossils.

**Resources**

Doyle, Peter. 1996. *Understanding Fossils: An Introduction to
Invertebrate Paleontology.* New York, NY: John Wiley & Sons, Inc.

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

**Reef Builder Cards**

**A House Made of Sponge?**

+-----------------------------------------------------------------------+
| -   I filter my food from the water around me.                        |
|                                                                       |
| -   I lived along the boundary between the reef and lagoon.           |
|                                                                       |
| -   My home is formed from two nearly identical shell halves.         |
|                                                                       |
| -   I am similar to modern day scallops.                              |
|                                                                       |
| ***Answer: pelecypod***                                               |
+-----------------------------------------------------------------------+

+-----------------------------------------------------------------------+
| -   I feed on algae growing on the ocean bottom.                      |
|                                                                       |
| -   My home is a coiled shell made of calcium carbonate.              |
|                                                                       |
| -   I move around on a wide, flat foot.                               |
|                                                                       |
| -   Today, you would refer to me as a common snail.                   |
|                                                                       |
| ***Answer: gastropod***                                               |
+-----------------------------------------------------------------------+

+-----------------------------------------------------------------------+
| -   I filter my food from the water around me.                        |
|                                                                       |
| -   I wasn't very common in the Permian Sea.                          |
|                                                                       |
| -   During the Permian Period, I was often found in the shape of a    |
|     horn.                                                             |
|                                                                       |
| -   I form many of the reefs found in the world today.                |
|                                                                       |
| > ***Answer: coral***                                                 |
+-----------------------------------------------------------------------+

+-----------------------------------------------------------------------+
| -   I filter my food from the water around me.                        |
|                                                                       |
| -   I lived along the top of the reef mound.                          |
|                                                                       |
| -   My home is formed from two shell halves that are not the same     |
|     size or shape.                                                    |
|                                                                       |
| -   My shell sometimes looks like it has wings.                       |
|                                                                       |
| ***Answer: brachiopod***                                              |
+-----------------------------------------------------------------------+

+-----------------------------------------------------------------------+
| -   I filter my food from the water around me.                        |
|                                                                       |
| -   I live in a colony with hundreds of other creatures just like me. |
|                                                                       |
| -   We were one of the main reef builders in the Permian Sea.         |
|                                                                       |
| -   Today, the remains of my home are often used as an absorbent      |
|     cleaning device.                                                  |
|                                                                       |
| ***Answer: sponge***                                                  |
+-----------------------------------------------------------------------+

+-----------------------------------------------------------------------+
| -   I filter my food from the water around me.                        |
|                                                                       |
| -   I live in a colony with hundreds of other creatures just like me. |
|                                                                       |
| -   Our home was often a pretty fan shaped structure attached to the  |
|     ocean floor.                                                      |
|                                                                       |
| -   My skeletal remains often look like little broken twigs.          |
|                                                                       |
| ***Answer: bryozoan***                                                |
+-----------------------------------------------------------------------+

+-----------------------------------------------------------------------+
| -   I filtered my food from the water around me.                      |
|                                                                       |
| ```{=html}                                                            |
| <!-- -->                                                              |
| ```                                                                   |
| -   I lived along the top and front of the reef, firmly attached to   |
|     the sea bottom.                                                   |
|                                                                       |
| -   One of my varieties looked like a beautiful water flower, but was |
|     really an animal.                                                 |
|                                                                       |
| -   My body is identified by its five-part symmetry.                  |
|                                                                       |
| ***Answer: Echinoderm or crinoid***                                   |
+-----------------------------------------------------------------------+

+-----------------------------------------------------------------------+
| -   I am a very important photosynthesizer in the ocean.              |
|                                                                       |
| -   I am one of the oldest organisms on Earth.                        |
|                                                                       |
| -   I helped form the reef by growing in great mounds that left large |
|     calcium carbonate deposits behind.                                |
|                                                                       |
| -   Gastropods feed on me.                                            |
|                                                                       |
| ***Answer: Algae***                                                   |
+-----------------------------------------------------------------------+

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**Old Salts**

***How did the massive salts beds near Carlsbad Caverns form?***

**Summary:** Students will build their own miniature "evaporite basin"
and record observations as salts begin to precipitate out of the water.

**Duration:** Two or three 50-minute class periods

**Setting:** Classroom or lab

**Vocabulary:** evaporite, precipitation, salinity, saturation

**Standards/Benchmarks Addressed:**SC2-E3, SC5-E2, SC6-E1

**Objectives**

Students will:

-   describe how the massive salt beds near Carlsbad Caverns formed.

-   make evaporite basins.

**Background**

![](media/image5.wmf){width="1.1020833333333333in"
height="1.2243055555555555in"}Guess what? The oceans are salty! Ok, that
should come as no surprise to anybody. However, the oceans contain more
than just sodium chloride, the compound you probably know as table salt.
As rivers flow downhill to some ocean, bay, or gulf they dissolve
minerals from the land they pass across or through. These dissolved
minerals take the form of ions, electrically charged atoms or groups of
atoms. The most common of these ions are sodium (Na^+^), chloride
(Cl^-^), magnesium (Mg^+2^), sulfate (SO~4~^-2^), calcium (Ca^+2^), and
potassium (K^+^). Additionally, carbon dioxide (CO~2~) dissolved in
water can form the carbonate ion (CO~3~^-2^). The combination of
electrically negative and positive ions results in a compound called a
"salt." The most common salt is table salt, or sodium chloride. It is
composed of a base unit of one sodium ion and one chloride ion.

In the ancient Permian Sea, the salinity of the water would change
periodically. Seasonal variations in temperature and freshwater input
are thought to have resulted in annual salinity cycles. On a longer
scale, the Delaware Basin would periodically be cut off from the Permian
Ocean due to changes in sea level or closure of the Hovey Channel to the
southwest. This would result in increased *salinity* as the water in the
basin began to evaporate. As the water evaporated, the concentration of
the less soluble salts would reach the *saturation* point and these
salts would begin to *precipitate* out of the water and settle to the
bottom, forming the thick deposits of *evaporite* rocks found there
today. If the water continued to evaporate and become more saline, the
more soluble salts would begin to precipitate. Eventually, as the
ancient Permian Sea was isolated from the Permian Ocean for the last
time, the most abundant salt, sodium chloride, began to precipitate and
the thick salt beds of the Salado Formation were formed. It is in this
formation that the WIPP repository is located. At some point during this
deposition, potassium chloride was deposited, forming the mineral
sylvite. The rock containing this mineral is commonly called potash and
is mined near Carlsbad.

Organisms living in the ancient sea used these salts to their advantage.
Many of them would extract the calcium and carbonate ions from the water
and use them to build shells of calcium carbonate, or what is also
referred to as the mineral calcite. This compound is the main component
of the rock limestone. Much of the sand along the reef was formed from
calcium carbonate precipitated out of the water or from the crushed and
ground skeletal remains of organisms. These carbonate sands filled in
voids in the reef and were trapped in the massive algal mats that formed
along the reef.

Over time, erosion has removed the overlying layers and exposed the reef
and the salts deposited in the basin. Calcium carbonate is much less
soluble than the other salts. In fact, in the semi-arid environment near
the Carlsbad Caverns, the limestone formed from this compound is
resistant to weathering and forms the bulk of the Guadalupe Mountains.
In the basin to the southeast of the Carlsbad Caverns, deposits of
gypsum (CaSO^4^) are exposed at the surface. Gypsum has a solubility
that is about ten times that of limestone. As a result, the gypsum in
the basin weathers faster than the limestone in the Guadalupe Mountains.
Groundwater moving through cracks in the gypsum beds has formed hundreds
of shallow caves near the surface. The largest of these, the Parks Ranch
Cave System, is over four miles in length and is located about six miles
south of White's City, within sight of the Carlsbad Caverns visitor
center. Salt beds do exist on the surface in some very arid parts of the
world, such as the region around the Dead Sea in Israel. Near Carlsbad,
annual rainfall and groundwater are sufficient to dissolve these salt
beds underground, before they are exposed at the surface.

**Materials**

-   measuring cup, 1 cup (250 ml)

-   measuring spoon, tablespoon (15 ml)

-   glass bowl, 2qt.

-   table salt

-   Epsom salts

-   scissors

-   hand lens

-   black construction paper

-   lid from large jar or shallow, flat bottomed bowl

**Procedure**

***Warm up:*** Ask the students how many have a parent or other relative
who works at a potash mine or at the Waste Isolation Pilot Plant (WIPP).
Ask in what kind of rocks the potash mines and the WIPP repository are
located. Discuss the thick beds of rock salt found near Carlsbad. Have
the students propose what conditions could have created beds of rock
salt 2000 feet thick. Point out that rock salt (halite) is not the only
evaporite mineral in the basin. Gypsum and limestone are also evaporite
rocks forming part of an evaporite sequence a mile thick.

In several places, such as the gypsum plain south of White's City, New
Mexico, we find some of the gypsum layers exposed on the surface. Ask
the students to brainstorm reasons that we do not find the halite beds
exposed at the surface. What happens to them when erosion causes them to
be near the surface?

***Activity***

> **Halite:**

1.  In a bowl, dissolve 4 tablespoons (60 ml) table salt in one cup
    (250 ml) water.

2.  Allow the bowl to sit undisturbed until the water evaporates (may
    take several weeks). If time will not allow for this, expose the
    bowl to moderate heat, such as an incandescent bulb to speed
    evaporation.

3.  Have the students study the crystals that form in the bottom of the
    bowl with a hand lens and draw what they observe. Have them compare
    the crystals in the bottom of the bowl with any they find along the
    sides of the bowl.

> **Epsomite:**

1.  Cut a circle from black construction paper that fits inside a large
    jar lid or in a flat-bottomed bowl.

2.  Dissolve four tablespoons (60 ml) Epsom Salts Mix in one cup
    (250 ml) water.

3.  Pour a thin layer of this solution over the black paper.

4.  Allow to stand overnight or longer, if necessary.

5.  Have the students study the crystals that form in the bottom of the
    bowl with a hand lens and draw what they observe.

Have the students compare and contrast the halite and the epsomite
crystals.

***Wrap Up:*** Discuss what happens to the salt dissolved in ocean water
if the ocean begins to evaporate. Ask which dissolves faster in a glass
of cool water, salt, or sugar? Using the students' knowledge that salt
dissolves easier, discuss the concept of solubility and the fact that
some substances dissolve easier than others. Ask the students if that
would mean that some substances would precipitate out, or form crystals,
easier than others. Discuss the three main salts found in the Delaware
Basin and how they formed at different times as the Permian Sea was cut
off from the Permian Ocean and began to evaporate.

**Assessment**

Have students:

-   name the three principal evaporite rocks found in the Delaware
    Basin.

-   explain why the rocks formed in separate layers, even though they
    all formed from the same evaporating body of water.

**Extensions**

Given a particular set of objectives or questions, have students design
and perform their own experiment related to solubility and salt. Some
suggested objectives are:

-   Using several salts, find out which one is the most soluble and
    which will precipitate out of the water first.

-   Does mixing two or more salts affect their solubility?

-   How does the temperature of water affect solubility?

**Resources**

Feather, Ralph, et al. 1999. *Glencoe Earth Science.* Westerville, OH:
Glencoe/McGraw-Hill.

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.

Van Cleave, Janice. 1991. *Earth Science For Every Kid.* New York, NY:
John Wiley & Sons, Inc.

![](media/image3.png){width="0.6in" height="0.8346456692913385in"}

**Is it Limestone, or did I get "Gyped?"**

***What types of rocks would have formed in the ancient Permian Sea?***

**Summary:** Students identify the primary rock types found in the area
around Carlsbad Caverns using properties such as color, grain size,
mineral content, and reactivity with acid.

**Duration:** Two 50-minute class periods

**Setting:** Classroom or lab

**Vocabulary:** sediment, sedimentary, texture

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

**Objectives**

Students will:

-   identify samples of limestone, gypsum, halite, sandstone, and shale
    using various chemical and physical properties.

**Background**

![](media/image6.wmf){width="1.4479166666666667in" height="1.875in"}The
principal rock types found near the Carlsbad Caverns National Park are
limestone, gypsum, halite, sandstone, and shale. All of these rocks are
sedimentary. They are formed from *sediments* deposited on or near the
Capitan Reef during the Permian Period, approximately 230 million years
ago. *Sedimentary* rocks fall under three classifications: clastic or
detrital, chemical, and organic.

Clastic, or detrital, sedimentary rocks are formed from the broken
remnants of other rocks. These broken remains, or sediments, can vary in
size from a fraction of a millimeter to several meters. They can be well
sorted, with only a narrow size range found within a rock, or they can
be a mix of sizes. Chemical cements deposited by groundwater moving
through the rock usually hold the sediments together. Sandstone,
siltstone, and shale are common clastic sedimentary rocks found in
Carlsbad Caverns National Park.

Chemical sedimentary rocks are rocks formed by chemicals precipitating
out of water. Most of the chemical sedimentary rocks near Carlsbad
precipitated out of the ancient Permian Sea. Gypsum, halite (rock salt),
and chemical limestone are examples of chemical sedimentary rocks found
in Carlsbad Caverns National Park. Many of the formations seen in the
caves of Carlsbad Caverns National Park also formed from minerals left
by evaporating water. For more information on the formation of chemical
sedimentary rocks, see the activity entitled "Old Salts."

Organic sedimentary rocks are rocks formed from or by living organisms.
Fossils are commonly found in organic sedimentary rocks. Organic
limestone and coquina limestone are two organic sedimentary rocks found
in Carlsbad Caverns National Park.

Identifying sedimentary rocks begins with determining whether the rock
is clastic, chemical, or organic. Then the actual rock type is
determined by studying the texture of the rock. Rocks made from larger
pieces or crystals are said to have a coarse *texture*. Rocks made from
smaller pieces or crystals are said to have a fine texture. Other
properties used to identify rocks are their color, taste, and reactivity
with certain acids. The table provided in the procedure will guide you
through the steps needed to identify the sedimentary rocks of Carlsbad
Caverns National Park. You will need to provide close assistance to
students in the early part of the activity.

**Materials**

-   several samples each of limestone, gypsum, halite, sandstone and
    shale

-   hand lenses

-   small sample of dilute HCl for teacher's demonstration

-   white vinegar

-   copies of data sheets and identification chart

**Procedure**

***Warm up:*** Divide class into groups of three or four students. Give
each group a rock from the materials list. Do not identify the rocks at
this time.

As the students to brainstorm a list of as many properties as they can
that could be used to describe their rock. Have the students share some
of their observations with the class. Write the observations on the
board and discuss similarities and differences in their observations.

Display the identification chart on a board or overhead projector.

Describe how the various types of sedimentary rocks are formed. Tell
students that they will be using this chart to identify rocks they are
given. Have students copy the identification chart.

***Activity***

1.  Give each group one sedimentary rock sample at a time. Do not give a
    new rock until the students have determined the name of the first
    one they were given.

2.  Have students classify the rock as clastic, chemical, or organic.
    Most will need assistance on the first rock.

3.  Have students determine the texture of the rock (sediment or crystal
    size, fossils)

4.  Have students list any fossils or minerals they see.

5.  Have students write any other observations they make. If they
    believe that they have limestone, they should request your
    assistance in placing a drop of vinegar on the sample and watching
    for it to fizz. Dilute HCl can be used, but only under strict
    supervision with goggles. After, rinse the sample thoroughly.

6.  Using the identification table, students determine the name of the
    rock and show you their data table and rock sample. If they are
    correct, they continue with another rock until they have tested six
    rocks.

***Wrap Up:*** On the back of their data table, as a class, or both,
have the students answer the following:

-   What properties best helped you identify clastic rocks? chemical?
    organic?

-   Describe one environment where sandstone might form.

-   If the mineral halite forms by evaporation, would it be clastic,
    chemical, or organic?

**Assessment**

Have students:

-   submit completed data sheets and answers to questions.

**Extensions**

Provide students with a cross section drawing of the Capitan Reef
similar to that on pages 8-9 in *Stories From Stones.* As a class or in
groups, discuss and attempt to determine where the sediments that formed
each of the rock samples used in the activity would have been deposited.

**Resources**

Feather, Ralph, et al. 1999. *Glencoe Earth Science.* Westerville, OH:
Glencoe/McGraw-Hill.

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

**Sedimentary Rock Identification Chart**

**Is it Limestone, or did I get "Gyped?"**

+------------------+---------------------------------------------------+
| > **Clastic or   |                                                   |
| > Detrital       |                                                   |
| > Rocks** (made  |                                                   |
| > from broken    |                                                   |
| > pieces of      |                                                   |
| > other rocks)   |                                                   |
+------------------+---------------------------------------------------+
| > **Name**       | > **Texture/Composition**                         |
+------------------+---------------------------------------------------+
| > Conglomerate   | > Rounded mix of sizes larger than 2mm in         |
|                  | > diameter - gravel                               |
+------------------+---------------------------------------------------+
| > Breccia        | > Angular mix of sizes larger than 2mm in         |
|                  | > diameter - gravel                               |
+------------------+---------------------------------------------------+
| > Sandstone      | > Made from cemented sand (0.06-2mm diameter) -   |
|                  | > sand                                            |
+------------------+---------------------------------------------------+
| > Siltstone      | > Made from powdered sediments, smaller than sand |
|                  | > in size - silt                                  |
+------------------+---------------------------------------------------+
| > Shale          | > Made from microscopic particles of other        |
|                  | > rocks - clay                                    |
+------------------+---------------------------------------------------+
| > **Chemical     |                                                   |
| > Rocks**        |                                                   |
| > (appear to be  |                                                   |
| > made of        |                                                   |
| > crystals)\*    |                                                   |
+------------------+---------------------------------------------------+
| > **Name**       | > **Identifying Properties**                      |
+------------------+---------------------------------------------------+
| > Limestone      | > gray/tan/light brown, fizzes in dilute HCl or   |
|                  | > Acetic Acid (vinegar)                           |
+------------------+---------------------------------------------------+
| > Rock Salt      | > colorless/white/blue, tastes like salt,         |
|                  | > dissolves easily in water                       |
+------------------+---------------------------------------------------+
| > Gypsum         | > white, forms long, slender crystals, or looks   |
|                  | > like crushed sugar                              |
+------------------+---------------------------------------------------+
| > \*Of the       |                                                   |
| > sedimentary    |                                                   |
| > rocks,         |                                                   |
| > limestone is   |                                                   |
| > hardest and    |                                                   |
| > gypsum is      |                                                   |
| > softest.       |                                                   |
+------------------+---------------------------------------------------+
| > **Organic      |                                                   |
| > Rocks**        |                                                   |
| > (identified by |                                                   |
| > fossils in     |                                                   |
| > them)          |                                                   |
+------------------+---------------------------------------------------+
| > **Name**       | > **Identifying Properties**                      |
+------------------+---------------------------------------------------+
| > Limestone      | > brown to gray crystalline rock with fossils     |
+------------------+---------------------------------------------------+
| > Coquina        | > large shell fragments, looks like Rice Krispy   |
|                  | > Treat                                           |
+------------------+---------------------------------------------------+

**Data and Observations**

**Is it Limestone, or did I get "Gyped?"**

+-----------+-----------+-----------+-----------+-----------+-----------+
| > *       | **Obser   | *         | **        | **        | **Rock    |
| *Sample** | vations** | *Minerals | Texture** | Detrital, | Name**    |
|           |           | or        |           | Chemical, |           |
|           |           | Fossils   |           | or        |           |
|           |           | Present** |           | Organic** |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
| **A**     |           |           |           |           |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
| **B**     |           |           |           |           |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
| **C**     |           |           |           |           |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
| **D**     |           |           |           |           |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
| **E**     |           |           |           |           |           |
+-----------+-----------+-----------+-----------+-----------+-----------+
| **F**     |           |           |           |           |           |
+-----------+-----------+-----------+-----------+-----------+-----------+

![](media/image3.png){width="0.6in" height="0.8346456692913385in"}

**Meet my Pet Fossil, Rocky**

***What are fossils and how do they form?***

**Summary:** Students will describe the various ways in which fossils
form, make a Plaster-of-Paris fossil, and attempt to describe an
organism and the environment in which it lived by studying its fossil.

**Duration:** Two or three 50-minute class periods

**Setting:** Classroom or lab

**Vocabulary:** cast, fossil, mold, paleontologist, petrified, trace
fossil

**Standards/Benchmarks Addressed:** SC2-E3, SC3-E1, SC5-E2, SC6-E1,
SC12-E5

**Objectives**

Students will:

-   describe the processes by which fossils form.

-   prepare a plaster-of-Paris cast/mold fossil.

-   study a fossil and attempt to describe the organism that left it and
    the environment in which it lived.

**Background**

![](media/image7.wmf){width="1.9791666666666667in"
height="0.9375in"}Dinosaurs\... Sixty-foot-long sharks\... Dragonflies
the size of a man\... Armadillos the size of a Volkswagen beetle\...

What do they have in common? They certainly don't exist today. However,
all of them did exist at one time and the way we know this is that we
have found and studied their remains. The remains, imprints, or traces
of living organisms left in rock are called *fossils*. From fossils, we
can tell not only what lived and where it lived, but how it lived, what
it ate, if it had a social structure, and many other valuable facts.

Most organisms do not create fossils. In fact, certain conditions are
necessary if organisms are to have a better chance of being preserved as
a fossil. First, a dead organism must be protected from scavengers or
decay caused by microorganisms. Organisms that are buried rapidly have a
much better chance of being preserved. In fact, many of the best fossils
found were deposited in or near swampy areas, where there was a greater
chance of rapid burial in non-oxygenated muds.

Jellyfish fossils are hard to find. This isn't due to a lack of
jellyfish, but rather it is due to a lack of hard parts in the
jellyfish. Hard parts such as bones, shells, or teeth make better
fossils. Sharks have been in the Earth's oceans since the Paleozoic Era,
but the most common shark fossils we find are teeth. The cartilage
skeleton of sharks rarely survives the fossilization process.

Fossils occur in many forms: petrified remains, carbonaceous films,
molds and casts, original remains, and trace fossils. *Petrified*
remains are turned to stone. As groundwater containing dissolved
minerals soaks into and through the buried organism, the minerals
replace the original tissues. With the deposition of these minerals, the
organism literally "turns to stone."

Carbonaceous films are fossils that can preserve evidence of softer
tissues. All organisms are composed of tissues that contain carbon. As
the organism is buried, heat and pressure change the structure of the
tissue, forcing gases and liquids from the body and leaving behind a
carbonaceous film. The resulting fossil shows the outline of the
original organism and sometimes details of the body structure as well as
the skeletal structure.

*Molds* and *casts* are formed when a fossil decays, erodes, or
dissolves away. The void left behind is called a mold. This void is then
filled with sediments washed in through cracks or by minerals that
precipitate out of groundwater. This new "replacement" fossil is called
a cast. Mold and cast fossils are quite common in the rocks of Carlsbad
Caverns National Park. In the activity associated with this lesson,
students will make mold and cast fossils.

Sometimes, *paleontologists*, scientists who study fossils, are
fortunate enough to find the actual remains of an organism. Any fan of
*Jurassic Park* is well aware of the existence of insect remains trapped
in amber. Amber is a rock made from sap. In the case of *Jurassic Park,*
insect's 175 million years ago were trapped and preserved in a drop of
tree sap. This protected the insects' body from decay or petrification
and, in the story line, even preserved DNA in the blood the insect had
ingested. A more realistic recent story centered on Mammoth remains
found frozen in ice. Other actual remains have been found in the La Brea
Tar Pit of California.

*Trace fossils* are evidence that an organism was there without any
remains present. Examples of trace fossils are tracks, drag marks,
wormholes, and burrows. From these fossils, it is possible to determine
such things as an organism's size, lifestyle, hunting behavior, and
diet.

Studying fossils provides clues to ancient environments as well.
Carlsbad Caverns National Park is located in the semi-arid northern
reaches of the Chihuahuan Desert at elevations ranging from around 3000
feet up to around 7500 feet. However, a quick look at the fossils of the
park reveals a time when a sea covered the area. Sponges, algae,
crinoids, mollusks, and brachiopods were common in this ancient sea and
we find their fossils today. Studying these fossils has provided
evidence of a massive barrier type reef that most believe was present
230 million years ago. Ongoing studies of the fossils in the park
continue to provide insights into the geologic history of the area.

**Materials**

-   paper bowls or butter tubs

-   plaster-of-Paris

-   leaf, shell, bone, or other materials to turn into fossils

-   petroleum jelly

-   actual fossils (if none are available, models or photos of fossils
    can be substituted)

-   old vinyl record, any size or artist will do

-   old, weathered bone

**Procedure**

***Warm up:*** Hold up an LP vinyl record for the students to view and
ask for them to describe what it is. Have them speculate how old it is
and what it would take to make it work. Ask them to describe the person
they think first owned it.

Hold up an old, weathered bone. Ask the students to describe the
organism that it came from. Ask them to speculate how old it is and what
part of the animal it came from.

Hold up a fossil for the class to view. Ask students to describe how it
is similar to and different from the two previous items.

Discuss the background material with the class, being sure to focus on
how fossils form, types of fossils, and what we can learn from fossils.

***Activity***

> **Making a Fossil** (Do in groups of three or four):

1.  Prepare plaster-of-Paris to that it is smooth and thick

2.  Fill bowl or tub with plaster to a depth of about one inch.

3.  Coat object to be fossilized (leaf, shell, bone, etc.) with a thin
    layer of petroleum jelly.

4.  Press the object into the plaster, but do not allow the plaster to
    flow over the top of the object.

5.  Allow the plaster to dry at least 24 hours and then remove the
    object.

6.  Coat the top of the plaster with a thin layer of petroleum jelly.

7.  Pour more plaster of Paris on top to a depth of about one inch and
    allow to dry for at least 24 hours.

8.  Separate the two halves. The original half represents a mold fossil
    and the second plaster poured represents a cast fossil.

> **Amateur Paleontologist Lab**

1)  Provide each group of students an actual fossil (models or photos
    can be substituted).

2)  Each group must study the fossil and provide their best answers to
    the following:

    a.  What is the name of the fossil?

    b.  How, and what, did the fossil eat?

    c.  How did the fossil move or how did it attach itself to the
        ground or ocean bottom?

    d.  Find one structure or object on the fossil and explain, in
        detail, what it was used for.

> 3\) Repeat with two or three other fossils.

***Wrap Up:*** Ask the students how easy it was to answer the
paleontologist lab questions. Ask students how they think a professional
paleontologist answers those questions. Lead the discussion to focus on
the present being the key to the past. In other words, the best
information we have to help us learn about the past is what we find on
Earth today.

Ask students to list points for and against the statement "the present
is the key to the past" and discuss as a class.

**Assessment**

Have students:

-   submit mold/cast fossils and Paleontologist Lab work to teacher.

-   Describe the necessary conditions for a fossil to form.

-   Describe five types of fossils.

-   List five important things that we can determine by studying
    fossils.

**Extensions**

Have students hypothesize what fossils would be left behind by today's
society. What would a paleontologist 230 million years from now think
about the organisms that were alive today? What would they think about
our eating habits, social structure, transportation, and entertainment?

**Resources**

Feather, Ralph, et al. 1999. *Glencoe Earth Science.* Westerville, OH:
Glencoe/McGraw-Hill.

Van Cleave, Janice. 1991. *Earth Science For Every Kid.* New York, NY:
John Wiley & Sons, Inc.

Carolina Biological Supply Company -- www.carolina.com

Fisher Scientific -- www1.fishersci.com

Flinn Scientific, Inc. -- www.flinnsci.com

Sargent-Welch -- www.sargentwelch.com