Materials Included In Kit

Additional Materials Required

Prelab Preparation

Cut polystyrene trays in half
Using scissors, cut the 5 included trays in half. Each student group gets two tray halves.  

Safety Precautions

Food dye coloring will stain skin and clothing. Follow all laboratory safety guidelines. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. All materials may be disposed of according to Flinn Suggested Disposal Method #26a.

Teacher Tips

• Enough materials are included in the kit for five student groups.
• Have students repeat steps 6–10 if needed to obtain more reliable observations and results.
• Large demonstration trays (Flinn Cat. No. AP5429) or cafeteria trays may be used to contain any sand that may escape the Fault Formation Trays. Alternatively, spread newspapers out on the benchtop to contain any spills and make cleanup easier.
• As an extension, have students investigate strike-slip faults using different substrates (e.g., soil, gravel) in the fault formation model. The effect of strike-slip faults on multiple layers of different substrates may also be studied.

Answers to Prelab Questions

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. Reverse fault—Occur when one portion of rock is pressed upwards relative to another portion of rock.
   3. Strike-slip fault—Occur where two portions of rock slide past one another without much upward or downward movement.
   4. Tension—Stretching forces that pull rocks apart at divergent plate boundaries.
   5. Compression—Squeezing forces that compress rocks together at convergent plate boundaries.

Sample Data

Part I. Creating a Strike-Slip Fault

Observations and Sketches

Part II. Strike-Slip Fault Types and Shearing

Observations and Sketches

Type of Strike-Slip Fault ___Left-lateral___

The “fence-row” across the fault line appeared to move to the left when the model was viewed from the perspective sketched below.

The rocks came in contact during this activity and started to grind, twist and turn as the right half of the fault formation model was moved.

Answers to Questions

1. Describe the first signs or types of deformation observed in step 6?

   Several small lines or cracks appeared the middle of the sand began to appear (see Figure A in Sample Data).

2. Explain what happened to these deformations as the strike-slip fault extended in steps 7 and 8.

   During step 7, the lines became longer and the space between the cracks became larger (see Figure B in Sample Data).

   During step 8, the cracks became very large and elongated. The ends of the cracks on the left half of the tray formed small “tails” that pointed toward the direction from which the right plate was moved. Some pileup of sand was noticed along the surface of the main fault line (see Figure C in Sample Data).

3. How did the faults formed in step 10 vary from the faults created steps 6–8?

   The faults formed in step 10 were much deeper, wider and more dramatic than the faults from steps 6–8. Since the sand was piled up in the center of the plate and was more centralized, more sand was being displaced as the model tray was moved (see Figure D in Sample Data).

4. What factors contributed to the wet sand in the model breaking along a single line (fault plane)?

   The center of the sand (parallel to the direction of the moving force) became a point of weakness in the model. Additional faults formed in an aligned cascading manner from where the main split (original point of weakness) in the sand occurred. The additional faults most likely formed and grew larger from additional weakness or “holes” in the sand as the right half of the tray was moved.

5. What event may occur when a strike-slip 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 form 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. Scientists “listen” to the Earth by continually monitoring vibrations. As vibrations intensity increases, an earthquake may occur.

Part II. Strike-Slip Fault Types and Shearing

7. What force(s) acted on the large rocks in this activity? What effect did this force have on the rocks?

   Shearing occurred when the rocks came in contact with each other. The force caused the rocks to grind, twist and turn upon contact when the fault moved the below them.

8. Describe how a river, road, and a building foundation might be affected by a strike-slip faults. Explain.

   Rivers—A river’s path could be altered and flow in a different path direction.
   Roads—Roads could shift and eventually break.
   Houses—House foundations could be twisted and warped.

9. Using online resources or a textbook, give actual examples of a left-lateral and right lateral strike-strip fault, respectively.

   The San Andreas Fault is an example of a right-lateral strike-slip fault. The Dead Sea area and the whole eastern border of Israel are example of left-lateral strike-slip faults.

Introduction

In this activity, the forces and processes involved in the faulting of the Earth’s crust will investigated. The main focus of this activity will be strike-slip faults. A hands-on model will be used to simulate the formation of strike-slip faults to study how they affect their surroundings.

Concepts

• Faults
• Shearing
• Strike-slip
• 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.

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. Models for strike-slip faults will be created and studied in this activity. Strike-slip or transform faults occur 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 moved to the right, the fault is known as a right-lateral strike-slip fault.

Experiment Overview

A sand landform model will be created and used to investigate strike-slip faults. The movements of strike-slip faults and their effects will be simulated, sketched and explored.

Materials

Prelab Questions

1. Define the following terms and explain the conditions under which they normally occur.
   a. Fault—
   
   b. Reverse fault—
   
   c. Strike-slip fault—
   
   d. Tension—
   
   e. Compression—

Safety Precautions

Wash hands thoroughly with soap and water before leaving the laboratory. Use caution with food dye solution as it will stain skin and clothing. Follow all laboratory safety guidelines.

Procedure

Part I. Creating a Strike-Slip Fault

1. Weigh out 250 g of sand and place it in a bowl or similar container.
2. Measure out 25 mL of water and add it to the sand in the bowl. Use a plastic spoon to thoroughly mix the water and sand.
3. Place the two halves of the Fault Formation Tray over a large tray or waterproof surface to contain any spills (spread out newspaper may be used). Make sure the inner surfaces of the two halves of the tray are completely flush with one another (see Figure 4).
   {12006_Procedure_Figure_4}
4. Holding the two halves of the tray together, place the wet sand into the Fault Formation Tray.
5. Assemble the tamper square by placing two washers over the shaft of the weld nut and placing the square plate over the weld nut shaft. Screw the handle into the weld nut. Use the tamper square to make the surface of the sand in the tray level and compact (see Figure 5).
   {12006_Procedure_Figure_5}
6. Holding both halves of the tray, gently push down on the right half of the tray and slide it forward slightly. Slide it just enough to see a subtle change on the surface of the sand (approximately 1 cm) (see Figure 6). Observe any changes in the sand and record and sketch all observations on the worksheet. Label the sketch Figure A. Continue to label all sketches on the worksheet during this activity.
   {12006_Procedure_Figure_6}
7. Continue exerting slow and steady pressure and slide the same half of the tray forward an additional 1 cm. Record and sketch all observations on the worksheet.
8. Slide the same half of the tray forward an additional 2 cm. Record and sketch all observations on the worksheet.
9. Place the two halves of the tray back together and arrange the sand so it forms a small hill that runs down the middle of the entire length of the tray (see Figure 7).
   {12006_Procedure_Figure_7}
10. Repeat steps 6–8 and observe any changes in the sand surface. Record and sketch all observations on the worksheet.
11. Answer the questions for Part I on the worksheet.

Part II. Strike-Slip Fault Types and Shearing

12. Return the Fault Formation Tray to its original flush position and repack the sand with the tamper square as was done in step 5.
13. Create a line on top of the sand using approximately 10 drops of food coloring (see Figure 8). The line of food coloring represents a fence line.
    {12006_Procedure_Figure_8}
14. Place two rocks on the surface of the sand as shown in Figure 9.
    {12006_Procedure_Figure_9}
15. Stand facing one of the long sides of the Fault Formation Tray (see Figure 10).
    {12006_Procedure_Figure_10}
16. Slide the right half (bottom) of the tray approximately 2 cm from its original position and the left half (upper) of the tray 2 cm from its original position in the opposite direction.
17. Look at the fence row across the fault line. If the fence line moved to the right of its original position, the fault is known as a right-lateral strike-slip fault. If the fence line moved to the left of its original position the fault is known as a left-lateral strike slip fault. Record the type of strike-slip fault that occurred on the worksheet.
18. Observe what happened to the two rocks on top of the sand and record all observations on the worksheet.
19. Consult your instructor for appropriate disposal procedures.
20. Answer the Questions for Part II on the worksheet

Student Worksheet PDF

12006_Student1.pdf