LAB 14

TEACHER’S PREPARATORY GUIDE /

Cracks in the Hard-Boiled Earth

Purpose

Students model some basic interactions of crustal plates—divergent boundaries, convergent boundaries, and transform boundaries—using the relative movement of shell fragments on a hard-boiled egg.

Time Required

One 45-minute class period

Lab Ratings

TEACHER PREP

STUDENT SET-UP

CONCEPT LEVEL

CLEAN UP

Advance Preparation

Prepare one hard-boiled egg per student. Cover eggs with water in a large saucepan or stockpot, and bring the water to a boil on a range top or Bunsen burner. Adjust the burner so that the water does not boil too rapidly (violent boiling may crack eggshells), and continue to boil for 15 minutes. Drain the water carefully, and rinse the eggs in cold tap water. If the hard-boiled eggs are stored overnight, they should be refrigerated.

You may wish to provide additional hard-boiled eggs for students to enjoy when they have completed the lab. If so, also consider having available salt or various spices, such as paprika, for students to sprinkle on their eggs before eating them.

If food coloring and paintbrushes are not available, you can substitute water-based markers. However, please note the safety concern below.

Safety Information

You may wish to use water-based markers instead of paintbrushes and food coloring. If so, be sure that students do not eat the eggs they use for this activity.

Teaching Strategies

You may wish to review the differences among the three types of plate boundaries before beginning this activity. Step 4, on page 67, may require some practice. Make sure that students do not squeeze the egg so hard it is destroyed.

Evaluation Strategies

For help evaluating this lab, see the Rubric for Performance Assessment in the Assessment Checklists & Rubrics

This rubric is also available in the One-Stop Planner CD-ROM.


Name ______Date ______Class ______

LAB 14

STUDENT WORKSHEET /

Cracks in the Hard-Boiled Earth

The Earth’s crust is made up of large plates that are in constant motion. As two adjacent plates move in two different directions, one of three types of plate boundaries is formed: divergent, convergent, or transform boundaries. Identifying these plate boundaries helps scientists better understand the processes occurring in the Earth. It can also serve a practical purpose, such as predicting earthquakes.

In this lab, you will use a hard-boiled egg to model the motion of crustal plates on the Earth’s surface.

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Ask a Question

What effects does the movement of crustal plates have on the Earth’s surface?

MATERIALS

·  hard-boiled egg

·  paper towels

·  thin paintbrush

·  small bottle of food coloring

·  magnifying glass

Conduct an Experiment

1.  Place the egg on the paper towel, and lightly tap the egg in different places to produce cracks of various lengths and sizes. Be careful not to tap too hard.

2.  Dip the paintbrush in the food coloring, and trace a number of the large cracks to make them more visible.

3.  Sketch both the front and rear views of the egg in the space provided on page 68, and show where the cracks are located. (See the illustration above.)

USEFUL TERMS

convergent boundary the boundary between two tectonic plates that push directly into one another

divergent boundary the boundary between two tectonic plates that move away from one another

transform boundary the boundary between two tectonic plates that slide past each other

4.  Gently squeeze the egg until slight movement occurs between the pieces of the shell. Use the magnifying glass to help you see the motion. You should be able to distinguish at least three types of motion between the pieces of the shell. Squeeze the egg in different ways to create these types of motion. Indicate on your sketch the motion of the eggshell pieces.

Analyze the Results

5.  What do the egg and the pieces of shell represent?


Name ______Date ______Class ______

Cracks in the Hard-Boiled Earth, continued

Egg Sketches

Front view of egg / Rear view of egg

6.  What do the cracks in the shell represent?

7.  Describe the patterns created by the cracks in the shell.


Name ______Date ______Class ______

Cracks in the Hard-Boiled Earth, continued

8.  Describe the three types of motion and their effects on the pattern of cracks.

9.  Relate these three types of motions to the three types of plate boundaries mentioned on page 67.

Draw Conclusions

10.  Look up the definitions for the following landforms:

·  caldera

·  volcano

·  mountain range

·  aquifer

·  rift valley

·  delta

·  strike-slip fault

·  cirque

Which of these landforms can be associated with the three types of plate boundaries? Identify the type(s) of motion.


Name ______Date ______Class ______

Cracks in the Hard-Boiled Earth, continued

11.  What are two weaknesses of using a hard-boiled egg to model the motion of the Earth’s crustal plates?

Going Further

You can also use a hard-boiled egg to model the interior structure of the Earth. Using a knife, slice the egg from this activity in two (including the shell), and identify which parts of the Earth the shell, the egg white, and the egg yolk represent. Note at least one strength and one weakness in this model.

Underlying content Copyright by Holt, Rinehart and Winston. Additions and changes to the underlying content are the responsibility of the instructor.

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