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South Carolina ETV
1101 George Rogers Boulevard
Columbia, SC 29201-4761
Phone: 803-737-3545

Stressed to a Fault! (Grade 8)

Master Teacher

Esther J. Thomas

Time Allotment

One 70-minute class period

Overview

Earth's picturesque landscapes, including majestic mountains, cascading waterfalls, verdant valleys, expansive plains, land-locked lakes and rolling hills, were and are still being sculpted by unseen forces within the crust.

These stress forces are a direct result of lithospheric plate movement and are responsible for the vast array of crustal deformations that define and compose Earth's natural scenery.

Unfortunately, the same stress forces that design the beauty of Earth's surface, can also produce catastrophic events such as earthquakes.

Using video, the Internet and hands-on activities in this lesson, students will learn how Earth's lithosphere is affected by the different types of stress that are produced by tectonic forces.

Subject Matter

Science

Learning Objectives

Students will be able to:

• Describe how stress in the Earth's crust is produced by the movement of the plates;
• Relate the three types of stress to the three types of plate movements;
• Explain how stress causes faulting;
• Describe the types of faults, and how movement along these faults changes the Earth's surface (crustal deformation);
• Construct models to illustrate the creation of faults in the Earth's crust;
• Predict what changes will occur in the surface features of a landscape as a direct result of movement along faults;
• Draw and correctly label diagrams to show: the parts of the fault, the type of fault illustrated, the type of stress that is being applied, and the direction of the stress force (use arrows) being applied.

South Carolina Standards

View SC Science Standards Web site

Grade 8 III B 1-g; 3-c

1. The Solid Earth is layered with a lithosphere, the hot, convecting asthenosphere within the mantle, and dense metallic core.

g. Examine how the lithosphere responds to tectonic forces (faulting and folding).

1. Major geologic events such as earthquakes, volcanic eruptions, and mountain building result from lithospheric plate motions.  Landforms and sea-floor features are the result of a combination of constructive (crustal deformation, volcanic eruptions, deposition of sediment) and destructive (weathering and erosion) processes.

c.  Examine how earthquakes result from forces inside Earth (tension, shearing, and compression).

Media Components

Video

The Earth Revealed, Lesson 8: "Earth's Structures."

Web Site

SAVAGE EARTH Animations:  SAVAGE EARTH Animated Graphics provides animation to illustrate lithospheric movements along 3 major types of faults. (Plug-in needed: Flash. It may be downloaded from this Web site.)

Materials

(Note to Teacher:  These quantities are based on 5 groups of 6 students each.)

• Silly putty or modeling clay (3 different colors per group)
• 6 butter knives (1 per group)
• wax paper
• 6 blue Sharpies ® (1 per group)
• 30 Styrofoam panel pieces (approximately 6½" x 1" sections/6 per group)
• Five 12-inch pieces of 2 x 4 lumber cut in half at a 45º or 135º angle and painted to resemble at least three horizontal rock layers. (1 per group, 1 for teacher) (Note to Teacher: Painting of wood blocks is optional.)
• 30 "Speaking of Stress" Activity Sheets (1 per student)
• Overhead transparencies: Illustration to show the parts of a fault

Equipment

• TV
• VCR
• overhead projector
• computer with Internet access
• AverKey

Prep for Teachers

• Bookmark Web site used in this lesson on each computer in the classroom.
• Cut (optional and paint) lumber sections.
• Divide the silly putty/modeling clay (3 colors/group).
• Pre-cut Styrofoam sections to 6½" x 1".
• Copy Activity Sheets.
• Preview video and cue segments.
• When using media, provide students with a Focus for Media Interaction, a specific task to complete and/or information to identify during, or after viewing of video segments, Web sites or other multimedia elements.

Introductory Activity

Step 1: Ask students what does it mean to be stressed or have stress. (Answers should be associated with experiencing pressure of some kind-mental or physical.)

Step 2: Divide students into groups. Distribute wax paper, 1 color silly putty/modeling clay and 2 Styrofoam strips to pairs of students within each group. Have students compare characteristics of the two substances.

(Silly putty/modeling clay is soft and pliable; Styrofoam is rigid and brittle.)

(Note to Teacher: Students are to work with the silly putty/modeling clay on the wax paper to protect the desk tops.)

Step 3: Instruct students to shape the silly putty/modeling clay into 2 rectangular strips, approximately 2 cm x 6 cm.

Step 4: Instruct students to take 1 putty/clay strip and push the opposite ends together. Repeat this procedure using 1 Styrofoam strip.

Have students take the ends of the other putty/clay strip between the fingers and slowly pull in opposite directions.  Repeat this action with the second Styrofoam strip.  Observe and record the results of each action.

Step 5: Ask: "Was there any difference in the way the silly putty/modeling clay responded when the same forces were applied to them?" "Why?" "What do you think these objects represent?"

(The silly putty/modeling clay folded, whereas the Styrofoam strip snapped when squeezed. When pulled apart, the silly putty/modeling clay stretched until it was thin in the center before separating completely, the Styrofoam snapped completely when pulled apart. The silly putty/modeling clay was softer, more pliable and flexible so it folded or stretched instead of breaking when subjected to force. However, the Styrofoam was rigid, less flexible, and more brittle, therefore it fractured very readily when force was applied. These objects represent the nature of Earth's lithosphere.  Newer crust is warmer, softer and more pliable than older crust which becomes more dense, rigid and brittle as it ages.)

Step 6: Show pictures of: *the aftermath of an earthquake (or different earthquakes); a changed landscape (river with a changed course, or waterfall, misaligned fence or road) as a result of movement along a fault; and/or folded rock layers and mountains. *A video clip of an earthquake in progress may be substituted.

Tell students that these events/surface features resulted from forces acting upon rocks in the Earth's crust in a manner similar to when they applied forces to the silly putty/modeling clay and Styrofoam strip. Rocks will also bend or break when subjected to stress.

Learning Activity

Step 1: Activate prior knowledge of lithospheric plate movements by asking if anyone can name and describe (or model with hand motions), the  types of plate movements at each of the three plate boundaries.

          

Step 2: Initiate discussion by asking students if there were any similarities in motion when comparing plate movements with the Introductory Activity. Have individual students share their explanations with the class.

(Discussion should lead to the fact that the same tectonic forces that trigger plate movement, also exert stress on sections of Earth's crust causing rocks to bend [folding], or break/fracture [faulting], thereby changing the surface of the crust and altering the landscape [crustal deformation].)

Step 3: Distribute Activity Sheet 1: "Speaking of Stress." Introduce vocabulary: compression, shearing, tension, deformation, fault, fault plane, footwall, hanging wall, elastic limit, earthquake, normal fault, reverse fault, strike-slip fault.

Instruct students to write down the definition or description of each term as it is introduced or described during the lesson.

Step 4: Use the overhead transparency of the illustrated parts of a fault and the wooden blocks to explain the parts of the fault. (Note to Teacher: This is a key to distinguishing between reverse and normal faults.)

                                               

Using the wooden blocks as a model, have students identify each part of a fault by correctly labeling the footwall, hanging wall, and fault plane.

Step 5: Tell students that they are going to view a video that illustrates and describes the types of faults. Insert in the VCR The Earth Revealed, Lesson 8: "Earth's Structure."

(tension)

Stress causing rocks to exceed this point will cause rocks to break or fracture. This is called:

(Elastic limit)

Name the stress that causes a mass of crust to slip sideways past another mass of crust.

(Shearing)

Name the type of fault that is created by shear stress.

(Strike-slip, also called lateral)

Name the type of fault that is created by the stress of compression.

(Reverse fault)

Name the type of fault that is created by the stress of tension.

(Normal fault)

Step 10: Provide a Focus for Media Interaction by having students watch and listen for the description and animation of each type of fault, and the stresses that create each. Pause tape as indicated, and pose the suggested questions during the course of viewing.

As an alternate activity, you may choose to replay the latter segment minus the sound, and have the students identify each type of stress and the resulting fault as indicated by the directional arrows shown in the video.

Step 11: Have students go to the bookmarked Internet site: SAVAGE EARTH Animations:  SAVAGE EARTH Animated Graphics and click on:

A. Normal Fault Animation

Tell them to:

1.  Identify the hanging wall and footwall.

     Designate each as being either on the left

     (L) or right (R) of the animation.

2.  Describe the movement of the hanging

     wall relative to the footwall.

3.  Draw an example of a normal fault and
     correctly label each part.

(Hanging wall( L ); footwall (R )

Hanging wall moves downward along the fault plane, footwall is above the hanging wall.                   

Tension is the stress.                                

B. Dip-slip Fault Animation (same as reverse fault)

Tell them to:

1.  Identify the hanging wall and foot wall.

     Designate each as being either on the left

     (L) or right (R)  of the animation.

2.  Describe the movement of the hanging

     wall relative to the footwall.

3.  Draw an example of a reverse fault and
     correctly label each part

4.  Draw arrows to show the direction of the
     stress that is being applied and name it

Hanging wall (R); foot wall (L)

Hanging wall moves upward along the fault plane.  Hanging wall is above the foot wall

Compression is the stress.

                                            

C.  Strike-slip Fault Animation

1.  Describe the movement along the fault.

Rock masses move sideways alongside each other.

Culminating Activity

Step 1: Distribute the remaining colors of the silly putty/modeling clay and Sharpies ® to each group. Instruct students to mold each color into three rectangular blocks and stack them on top of each other to simulate layers of rock.

Step 2: Instruct students to use the butter knife to cut the stacked clay blocks at an angle. Keep the severed blocks together. Students should refer to their drawings of the faults to determine which side is the hanging wall and which is the footwall. Use the blue Sharpie ® to label each side.

Step 3: Tell students to draw a line across the surface of their model to show a river (any body of running water). The flow of water should be from the hanging wall to the footwall. Use a directional arrow to indicate the direction of water flow.

Step 4: Ask students to simulate each of the three faults they studied and tell how each would impact the flow of the river. Would any surface features be created or changed as a result of movement along each fault?

(Normal fault: the river will create a lake at the footwall edge of the fault since that end will be at a higher elevation than the hanging wall; reverse fault:  the river will cascade over the hanging wall as a waterfall since it is at a higher elevation than the footwall; strike-slip (lateral) fault:  the river's course will be changed sideways in the direction of fault movement.)

Assessment

The Assessment for this lesson will be based upon the student's ability to:

• Correctly identify and label the types of stress being applied to rocks.
• Associate each type of stress with  a similar type of tectonic plate movement.
• Draw and accurately label illustrations to show each of the three types of faults.
• Evaluate a landscape with a river and predict what surface changes would occur as a result of movement along each type of fault.

Cross-Curricular Extensions

Language Arts: Since South Carolina is a seismically active state, students can research some of the active faults that exist here. They may choose one of their interest, and write an essay or report telling what kind of fault it is, and how movement along this fault has affected/impacted this state, past or present.

Art: Have students illustrate the types of faults by drawing and coloring them; have students use modeling clay or silly putty to create models of each type of fault.

Community Connections

Invite Dr. Pradeep Talwani, a seismologist at USC, Columbia, to speak to the class, or ask a member of USGS to visit the classroom to discuss fault movement in the state of South Carolina.

Student Materials

• Silly putty/modeling clay (3 different colors per group)
• wax paper (to protect working surface)
• Styrofoam panel strips (approximately 6½" x 1" sections, 6 per group)
• 12" section of 2x 4 lumber cut at an acute or obtuse angle. (1 per group)
• 1 sheet per student:  "Terms of Stress" vocabulary sheet. (Activity Sheet 1)

Activity Sheets (PDF)

• Activity Sheet 1

Answer Keys (PDF)

• Activity Sheet 1 Answers