# Modeling Faults

## Student Activity Kit

### Materials Included In Kit

Foam sheets, 5½" x 8½", 50
Rubber bands, 45

(for each lab group)
Marker
Ruler
Scissors

### Prelab Preparation

1. Using sharp scissors or a paper cutter, cut each foam sheet into 1¾" x 8½" strips. Three of these strips should be obtained from each foam sheet (see Figure 9).
{12689_Preparation_Figure_9_View from top of foam sheet}
2. Sort the foam strips so that each student group receives two strips each of three different colors (total of 6 strips).

### Safety Precautions

Remind students to wash their hands thoroughly with soap and water before leaving the laboratory.

### Teacher Tips

• Enough materials are provided in this kit for 30 students working in pairs, or for 15 groups of students. This laboratory activity can reasonably be completed in one 50-minute class period.
• The 1¾" x 8½" strips may be cut by the students before class if time allows.
• Foam glue may be purchased from a local craft store to create permanent fault models if desired.
• Have students perform further research on earthquakes and the Richter scale. Flinn Scientific, Inc. sells a Find the Epicenter of an Earthquake Kit (Flinn Catalog No. AP7266) that is a great companion to this activity.
• This activity is a great way to introduce plate tectonics as well—see the Pangaea Activity Kit available from Flinn Scientific (Catalog No. AP7170) for a laboratory simulation of plate tectonics.

### Science & Engineering Practices

Developing and using models

### Disciplinary Core Ideas

MS-ESS2.B: Plate Tectonics and Large-Scale System Interactions
HS-ESS2.B: Plate Tectonics and Large-Scale System Interactions

### Crosscutting Concepts

Cause and effect
Systems and system models
Stability and change

### Performance Expectations

HS-LS2-2: Use mathematical representations to support and revise explanations based on evidence about factors affecting biodiversity and populations in ecosystems of different scales.
HS-LS2-7: Design, evaluate, and refine a solution for reducing the impacts of human activities on the environment and biodiversity.
HS-LS4-6: Create or revise a simulation to test a solution to mitigate adverse impacts of human activity on biodiversity.
MS-LS1-5: Construct a scientific explanation based on evidence for how environmental and genetic factors influence the growth of organisms.
MS-LS2-4: Construct an argument supported by empirical evidence that changes to physical or biological components of an ecosystem affect populations.

### Sample Data

Normal Fault Sketch

{12689_Data_Figure_10}
Normal Fault Observations

The right portion of land/rock dropped downward compared to the left portion of land/rock. The green layers of the right portion of land/rock is now even with the yellow layers of the left portion of land/rock.

Reverse Fault Sketch
{12689_Data_Figure_11}
Reverse Fault Observations

The right portion of land/rock moved upward compared to the left portion of land/rock. The blue layers of the right portion of land/rock are now even with the yellow layers of the left portion of land/rock.

Strike-Slip Fault Sketch
{12689_Data_Figure_12}
Strike-Slip Fault Observations

Two strike-slip faults were simulated causing the river to “break” or become jagged in two separate locations.

1. Define the following terms and explain the conditions under which they normally occur.
1. Fault—a fracture in rocks where rocks not only crack but move alongside each other.
2. Tension—stretching forces that pull rocks apart at divergent plate boundaries.
3. Compression—squeezing forces that compress rocks together at convergent plate boundaries.
4. Shearing—forces that push on rocks from various directions causing them to twist and break.
2. Complete the following table.
3. What type(s) of strike-slip faults were formed in step 13? Label these types of faults on the strike-slip diagram you sketched.

Answers will vary. Both left-lateral and right-lateral strike-slip faults should be formed. See sample strike-slip diagram in the Sample Data.

4. What happened to the river as the land sections underwent strike-slip faults? How would this affect the course of the river?

The river’s path was altered when the strike-slip movement occurred at the fault. Eventually the river may wander and run a new course.

5. What event may occur when a fault forms? Describe this process.

An earthquake may occur. When a fault is created, the rocks slide past or rub against each other in different directions. The energy created and released may cause an earthquake. Most earthquakes occur along tectonic plate boundaries.

6. Why is it easier to predict where an earthquake will occur rather than when it will occur?

Most earthquakes happen near plate boundaries where earthquakes have previously occurred. The actual time an earthquake will occur is much more difficult to predict.

7. Using online resources, perform further research and give actual examples of a normal fault, reverse fault, and strike-slip fault.

The Sierra Nevada Mountains are examples of normal faults. The Himalaya Mountains were formed mainly by reverse faults. The San Andreas fault in California is the most famous example of a strike-slip fault.

# Modeling Faults

### Introduction

Explore the three main types of geological faults and how they form using this hands-on modeling activity.

### Concepts

• Normal faults
• Strike-slip faults
• Reverse faults
• Earthquakes

### Background

As molten rock material moves through the Earth a great deal of pressure is created. The pressure builds up in the rocks until the rocks reach a breaking point and can no longer bend or stretch. As the rocks break, they move along surfaces or cracks called faults. When a fault is created, the rocks slide past or rub against each other in different directions. The energy created and released by this phenomenon creates vibrations in the Earth called earthquakes. Most earthquakes occur along tectonic plate boundaries.

At divergent plate boundaries, or areas where plates are spreading apart, rocks are subjected to stretching forces known as tension. Tension can pull apart rocks and create normal faults. A normal fault occurs when a portion of rock drops downward relative to another portion of rock (see Figure 1). Normal faults are the result of the expansion of the Earth’s crust.

{12689_Background_Figure_1_Normal fault}
Reverse faults occur when one portion of rock is pressed upwards relative to another portion of rock (see Figure 2). Compression forces at convergent plates (areas where plates are being pushed together) are responsible for reverse faults. The compression pushes on rocks causing them to bend and break and move along a reverse fault surface.
{12689_Background_Figure_2_Reverse fault}
A transform or strike-slip fault occurs where two portions of rock slide past one another without much upward or downward movement (see Figure 3). Rocks exposed to strike-slip faults are subject to shearing. Shearing forces push on rocks from different directions. As the rocks move past each other, their surfaces rub upon each other and cause a large amount of strain or twisting. Irregular surfaces of rock are created that hinder the movement of the plates. In these areas a large amount of stress is created and as the rocks reach their elastic limit, they break and earthquakes result. If an object such as a road or riverbed has been moved to the left of its original position due to a strike-slip fault, the fault is known as a left-lateral strike-slip fault. Conversely, if an object has been move to the right, the fault is known as a right-lateral strike-slip fault.
{12689_Background_Figure_3_Strike-slip fault}

### Experiment Overview

A model landform section consisting of multiple layers will be created to compare and contrast the three main types of faults—normal, reverse and strike-slip faults. The movements of each type of fault will be simulated, sketched and their impact will be explored.

### Materials

Foam strips, 1¾" x 8½", 6 (2 strips each of 3 different colors)
Marker
Rubber bands, 3
Ruler
Scissors

### Safety Precautions

Wash hands thoroughly with soap and water before leaving the laboratory. Follow all laboratory safety guidelines.

### Procedure

1. Obtain six strips of foam (two strips each of three different colors). Each strip is 1¾" wide by 8½" long.
2. Stack the foam strips on top of one another. The two strips of each color should be next to each other (see Figure 4). The stacked strips represent a layered cross section of land, with each color representing a different rock layer.
{12689_Procedure_Figure_4_Side view}
3. Using a marker, draw two lines down the center of the top strip as shown in Figure 5. These lines represent a river.
{12689_Procedure_Figure_5_View from top}
4. Using a ruler, measure 2½" inches from one side of the top of the stacked strips. Use a marker to place a small mark on the top foam strip at this location (see Figure 6).
{12689_Procedure_Figure_6}
5. Repeat step 4 on the other side of the strip.
6. Using scissors, make a diagonal cut starting at the 2½" mark on one side as shown in Figure 7. For best results, cut each strip individually.
{12689_Procedure_Figure_7_View from top}
7. Repeat step 6 on the other side of the strips as shown in Figure 7.
8. The cuts that were made in steps 6 and 7 represent faults in the land. Sketch the cross section of land and the faults on the Modeling Faults Worksheet.
9. Rubber band each of the three land sections as shown in Figure 8.
{12689_Procedure_Figure_8_View from top}
10. Hold on to two of the land sections that are touching one another. Simulate a normal fault. Observe the locations of different layers of rock relative to one another. Sketch and record all observations, including the overall movement of rock land masses, on the Modeling Faults Worksheet. Label the foam layer colors as well.
11. Using the same two land sections, simulate a reverse fault. Observe the locations of different layers of rock relative to one another. Sketch and record all observations on the Modeling Faults Worksheet. Label the foam layer colors as well.
12. Return all three land sections to their original positions.
13. Simulate two strike-slip faults using all three of the pieces.
14. Sketch and record all observations on the Modeling Faults Worksheet. Be sure to pay close attention to the river drawn on the top foam layer.