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

*Middle School Geology*

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Caves, Canyons, Cactus & Critters

Geology Curriculum

# Clams Got Wings! An exploration of uplift and mountain building. 31

1.  **You're stressing me out!** Activities designed to demonstrate\
    stresses in the Earth's crust. 32

2.  **Achy Breaky Earth** Students will build cardboard or clay\
    models demonstrating the three major types of faults and\
    the three major types of folds. 34

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**Clams Got Wings!**

When I was ten years old, my family took a trip to the mountains. While
there, we went for a walk in a meadow at an elevation of around 3000
meters. In that field were the first fossils I ever found. There was
something about those fossils that I didn't understand, however. They
were fossils of snails and clams in excess of six inches. I was smart
enough to know that they were from animals that lived in an ocean
environment but I couldn't figure out how they ended up on the top of a
mountain in New Mexico, far from any ocean.

A study of the earth's history reveals a planet whose outer layer
flexes; some areas rise and fall many times as tectonic plates collide
or pull apart. The highest mountain in the world is topped by marine
limestone formed in an ocean between Eurasia and India in the distant
past. The movement of tectonic plates on the earth's surface creates
great stress in the crust. As a result of this stress, the crust is
stretched, folded, and broken in many places.

In this unit, students will be introduced to stresses that shape the
earth's surface. They will have the opportunity to learn how to identify
the various faults and folds geologists study.

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**You're Stressing Me Out!**

***What kinds of stress in the earth cause\
earthquakes, volcanoes, and build up mountains?***

**Summary:** Students demonstrate the various forms of stress found in
the earth's crust.

**Duration:** One 50-minute class period

**Setting:** Classroom

**Vocabulary:** compression, shear, stress, tension

**Standards/Benchmarks Addressed:** SC2-E1, SC4-E1, SC4-E5, SC5-E2,
SC6-E1, SC12-E3

**Objectives**

Students will:

-   describe tension, compression, and shear.

**Background**

![](media/image4.wmf){width="1.84375in" height="0.96875in"}As the
lithospheric plates move around on the surface of the earth, a
significant amount of *stress* builds up along their boundaries. This
stress can be in the form of *compression* where plates are colliding,
*tension* where a plate is being pulled apart, or *shear* where plates
are sliding sideways past each other.

As plates collide, compression forces the rocks at the boundaries to
fold, or, when their elastic limit is reached, to break. These breaks
are known as reverse faults. Earthquakes are common in these areas. The
Andes Mountains of South America are found along the converging boundary
of the South American and Nazca Plates. The mountains and volcanoes of
southern Europe are formed along the converging African and Eurasian
plates.

Tension is the stress created when a plate begins to split or when
plates begin to pull apart. As the rocks along one of these boundaries
reach their elastic limits, they begin to break in normal faults. The
stretching of rocks and the dropping of faulted blocks along this
boundary creates low areas called rift valleys. One of the best-known
divergent boundaries is found along the Mid-Atlantic Ridge, where the
South American and North American plates are moving away from the
African and Eurasian plates. Another example of a rift valley is the Rio
Grande rift that runs north to south through central New Mexico. Results
of this rifting are the north-south mountain chains bordering the Rio
Grande, such as the Sandia Mountains, and much of the historical
volcanic activity of central New Mexico.

Shear occurs when two plates slide sideways past each other with very
little vertical movement. The fault created by this boundary is called a
slip-strike fault. Drag along the boundary, due to friction between the
plates, results in additional stress. This stress creates a series of
other faults that radiate away from the boundary. Periodic earthquakes
serve to relieve this stress. A widely known example of a slip-strike
fault is the San Andreas Fault of California.

In this activity, the focus will be on understanding the various forms
of stress that build in the crust as the lithospheric plates move. The
next lesson, *Achy Breaky Earth,* will explore the faults and folds that
occur as a result of stress.

**Materials**

-   clay -- enough for each student or group to have three 4\"x6\"x1/2\"
    layers

-   wax paper

-   paper to sketch and write notes

**Procedure**

***Warm up:*** Show the students pictures of an area after an
earthquake. Ask the students to describe the destruction they observe.
Ask them "What caused this damage?" Once an earthquake has been
determined to be the cause, ask, "Would you say that energy was released
by this earthquake?" Ask students what they believe the source of that
energy to be.

***Activity***

1.  Have students place the three pieces of clay separately on pieces of
    wax paper.

2.  With their hands, have the students slowly begin to push on opposite
    ends of one of the pieces, causing it to compress. Have them sketch
    what they observe.

3.  Have the students hold the second piece of clay in their hands and
    begin to slowly pull it apart. Again, have the students sketch what
    they observe.

4.  While holding one side of the last piece of clay flat on the wax
    paper, have the students begin slowly pushing the other side
    sideways with their other hand so that one hand slides past the
    other. Again, have the students sketch what they observe.

***Wrap Up:*** Ask students the following questions:

-   What happens to the clay when your hands compress it from opposite
    directions?

-   What happens to the clay when you stretch it?

-   What happens to the clay when you push it so that your hands slide
    past one another?

Discuss the concept of stress in the earth's crust and its possible
sources. Describe tension, compression, and shear and relate them to the
students' clay samples.

**Assessment**

Have students:

-   define stress and describe its causes in the earth's crust.

-   describe tension, compression, and shear and give examples of what
    types of structures develop in the earth's crust as a result of
    each.

**Extensions**

Look at aerial or satellite photos and attempt to find areas on the
earth's surface where stress is found. A tectonic map of the earth's
surface such as those found in most Earth Science textbooks would be
helpful. At each location, have students attempt to determine the type
of stress present.

**Resources**

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

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**Achy Breaky Earth**

***What are the different types of breaks and folds in the Earth
called?***

**Summary:** Students describe and prepare models of various faults and
folds.

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

**Setting:** Classroom

**Vocabulary:** anticline, elastic limit, monocline, normal fault,
reverse fault, slip-strike fault, syncline

**Standards/Benchmarks Addressed:** SC2-E1, SC2-E3, SC4-E1, SC4-E5,
SC5-E2, SC6-E1, SC12-E3

**Objectives**

Students will:

-   describe the three primary types of faults (normal, reverse,
    slip-strike).

-   describe the three primary types of folds (syncline, anticline,
    monocline).

-   build clay or cardboard models demonstrating the various faults and
    folds.

![](media/image5.wmf){width="1.6in"
height="1.3833333333333333in"}**Background**

The stresses in the earth that were discussed in the lesson titled
*You're stressing me out!* result in faulting and folding at the
boundaries of the earth's tectonic plates. In this activity, students
will be identifying the various types of faults and folds, as well as
building models to represent them.

As stress is applied to an object, that object will begin to give, to
fold, or bend. Some objects, such as clay, bend easily. Other objects,
such as rocks, required a great deal of heat and pressure before they
bend. The folds that form in mountains are a result of compression. An
upward fold is called an *anticline* and a downward fold is called a
*syncline.* A fold on which there is only a single slope is called a
*monocline*.

![](media/image6.wmf)![](media/image7.wmf)

There is a limit to how far things can bend and stretch. This is called
the *elastic limit*. Once this point is passed, the object will break,
whether it is a rubber band or a rock. If rocks break and movement
happens along the break, it is called a fault. A fault caused by
compression, in which one block slides up and over the other, is called
a *reverse fault*. A fault caused by tension, or stretching, in which
one block sinks relative to the other, is called a *normal fault*. A
fault caused by shear, in which one block slides sideways along another
with very little vertical movement, is called a *slip-strike fault.*

![](media/image8.wmf)

![](media/image9.wmf)

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Faulted mountains are found many places in the world. One of the most
spectacular regions is the Himalayas where the Indo-Australian plate is
colliding into the Eurasian plate. Compression forces have raised
ocean-formed limestone to an elevation of over 8,000 meters in that
area. In the western United States, stretching of the North American
plate has resulted in many north-south trending fault-block mountain
ranges. These mountains form the Basin and Range Province of the
southwest. The abrupt edges of the mountain ranges mark a series of
normal faults with displacements often in excess of one mile. The
Guadalupe Mountains, in which Carlsbad Cavern is located, is an example
of a fault-block range. The most spectacular evidence of this is found
along the western escarpment near Guadalupe Peak and is clearly visible
from Salt Flat, Texas.

On the earth's surface, large scale faulting and folding result in long,
linear features when photographed from space. Planetary geologists look
for these features as evidence of tectonic activity on other planets.
Using these features for clues, they have been able to determine that
other planets in our solar system have also experienced tectonic
activity. On several planets, they have found evidence of geologic
activity that is ongoing. In this lesson, students will be asked to look
at maps and try to find surface features on earth that would provide
evidence of tectonic activity.

**Materials**

-   textbooks showing diagrams of the varieties of faults and folds

-   maps showing surface features such as mountain ranges and river
    valleys

-   wax paper

-   clay

-   cardboard boxes

-   crayons or markers

-   scissors

-   tape, paste, or glue

**Procedure**

***Warm up:*** Have students study the maps and look for features that
have some sort of a regular form or shape (linear, round, or oval,
etc.). Discuss with the students what might cause these shapes to form
on the earth's surface. The discussion should include plate tectonics
and the resulting faults and folding.

Using drawings on overheads or the board, as well as textbook sketches,
describe and discuss the various faults and folds with the students.

***Activity***

> **Faults**

1.  Cut and tape, or paste, cardboard boxes to make two "fault blocks"
    per group, or per student, with one side sloped at about 30^o^ as
    shown below. ![](media/image11.wmf)

2.  Color layers on the boxes that match on both sides. Students can
    even build little towns (Monopoly house size) on the top of the
    blocks if they wish.

3.  When the blocks are finished, students can slide them along the
    fault to model reverse, normal, and slip-strike faults.

> **Folds**

1.  Layer together two colors of modeling clay in a rectangle about
    3\"x6\"x1\". Prepare three blocks in this manner.

2.  Place one block of clay over a gap of about four inches between two
    books. Place a small weight in the middle. Have students sketch what
    happens. The fold formed will be a syncline.

3.  Lay one of the clay blocks on a piece of wax paper. Have the
    students push the ends of the clay together slowly, as shown below.
    The fold formed will be an anticline.

> ![](media/image12.wmf)

4.  Place another block of clay on a book with about one to two inches
    of clay on the book and a weight on the clay over the book to hold
    it in place. Let the remainder hang over the edge. The fold formed
    will be a monocline.

***Wrap Up:*** Discuss the various forms of stress that accounted for
the various faults and folds. Have students sketch and label each one.

**Assessment**

Have students:

-   name each fault and fold correctly when shown a model or drawing.

-   describe the stress or forces in the earth that account for faulting
    and folding.

**Extensions**

Obtain photos of other planets or moons. Have the students study the
photos for evidence of faults or folds. Have the students describe what
this evidence indicates about that planet.

**Resources**

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

Sprinkel, D.A., Chidsey, T.C., and Anderson, P.B., editors. 2000.
*Geology of Utah's Parks and Monuments.* Salt Lake City, UT. Utah
Geological Association, publication 28.

VanCleave, Janice. 1991. *Janice VanCleave's Earth Science For Every
Kid.* New York, NY, John Wiley & Sons, Inc.