Hands-on Activity: Scale Model of the Earth
Contributed by: Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

 SummaryStudents gain an understanding of the layers of the Earth by designing and building clay models.
 Engineering Connection Relating science and/or math concept(s) to engineering Engineers frequently use scale models and computer simulations to test concepts without wasting costly resources. Constructing scale models of the Earth assists engineers in the design of instruments that help predict earthquakes. It also aids in the development of robots that travel deep into the different layers of the Earth. Engineers also use small-scale models of our planet to understand the relative size of the Earth, model space flight orbits around the Earth, and predict how the Earth might change over time.

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 Grade Level: 5 (3-5) Group Size: 2 Time Required: 50 minutes Activity Dependency :None Expendable Cost Per Group Keywords: My Rating: Avg Rating: Not Yet Rated.Teacher Experiences  |  Share your experience!

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Educational Standards :

•   Common Core State Standards for Mathematics: Math
•   International Technology and Engineering Educators Association: Technology
•   Next Generation Science Standards: Science

After this activity, students should be able to:
• Describe the layers of the Earth.
• Make a scale model.
• Compare a model of the Earth with what it represents.
• Explain why engineers need to learn about the Earth's structure.

Each group needs:
• 3 small balls of clay or Play-Doh® in three colors: red, orange and yellow
• ¼ cup fine sand
• 12-inch ruler
• fishing line, 12 inches
• calculator (optional for scaling worksheet)
• samples of various newspaper articles on any topic
• (optional) Earthquakes Journal Page (see attachments)

The Earth is a sphere made of several layers: the inner core, outer core, mantle and crust. (Draw Figure 1 on the classroom board, or show students a suitable diagram or projected image.) The inner core, mantle and crust are solid, and the outer core is molten, or liquid. The crust is the thinnest layer of the Earth and is the layer on which we live. The inner core, outer core and mantle experience extremely high pressures and temperatures.
Most research about the Earth comes from studying the crust. Can you guess why? (Listen to student ideas.) Well, if we tried to travel all the way to the Earth's inner core, we would be crushed into pieces from the very high pressure, and be burned up from the extreme heat! It is not a friendly environment for humans. The solid crust "floats" along in plates very slowly on top of the mantle. The mantle is considered to be a solid. Some scientists describe it as having the consistency of warm wax or warm asphalt, or even silly putty. Even in high-pressure and high-temperature conditions, it can move (deform) only very slowly, perhaps a few centimeters a year. In the crust layer, sometimes the plates collide, or stick together, and when this happens, earthquakes occur.
Who can tell me what a "scale model" is? (Listen to student ideas.) A scale model is a smaller or larger version of an object. It is made to be the same as the original object but at a different size than the real object. You could think of a doll as a smaller scale model of a person. Or a toy car as a smaller scale model of a full-size car. A scale model has the same shape and components and relative proportions as the actual object. It is measured to a "scale" that corresponds to the actual size. For example, perhaps 1 inch corresponds to 1 foot. Engineers sometimes build detailed scale models of objects to observe how parts fit together and/or move. Building scale models of the Earth can help engineers plan the routes and orbits of space flights, or design instruments that help predict earthquakes, or invent robots to travel into the different layers to collect data. In this activity, we will make a model of the Earth's layers. For our purposes, 1 centimeter will equal 1,000 kilometers.

Background Information

A commonly held misconception is that the Earth's mantle is liquid because we refer to the lower portion of it as being "fluid." However, the most widely accepted current scientific understanding is that the mantle is solid.
The mantle consists of two regions. The upper region is part of the lithosphere; it is very rigid and exists as the bottom of our tectonic plates. The lower region is part of the asthenosphere and is referred to as "fluid," which is not in reference to its phase of matter, but rather to the plasticity of the asthenosphere. Because the mantle exists under such extreme heat and pressure (~1,000° Celsius), it is ductile, like warm soft wax or asphalt, or silly putty, and is capable of moving and deforming at really slow rates of a few centimeters per year. The evidence that has convinced scientists that the mantle is solid comes from the study of seismic waves. We know that S waves are capable of moving through solids, but not through liquids. Scientists have recorded S waves moving through the mantle (evidence that it is solid), but not through the outer core (evidence that it is liquid).

Before the Activity

• Make your own clay or Play-Doh model of the Earth to use for demonstration purposes.

With the Students

1. Draw an Earth layers diagram on the board, or show Figure 1 as an overhead transparency.
 Figure 1. Layers of the Earthcopyright
1. Introduce the concept of a scale model. (A scale model is a copy of something that has been reduced or increased by a certain factor.)
2. Show students the clay model of the Earth that serves as an example of what they are going to create.
3. As a class, and if time permits, have groups convert the layers' thickness from miles to kilometers, feet, or meters (see answers below). Write the answers on the board.
Inner core = 800 mi = 1,287 km = 1,287,000 meters = 4,224,000 ft
Outer core = 1400 mi = 2,253 km = 2,253,000 meters = 7,392,000 ft
Mantle = 1800 miles = 2,897 km = 2,897,000 meters = 9,504,000 ft
Continental plate = 15 miles = 24 km = 24,000 meters = 79,200 ft
Explain to students that for each layer of their models, one centimeter represents 1,000 kilometers. Have them round up or down the kilometers to convert the thickness dimensions to centimeters.
1. Have students form the inner core using the red clay. (The ball of clay representing the inner core should have a diameter of about 1 centimeter.)
2. The second layer of the model is the outer core. Use the orange clay to add ~2 cm layer over the red ball of clay (their inner core). The outer core layer, when added, brings the diameter of the ball to about 3 centimeters.
3. The third and final model layer is the mantle. Use the yellow clay to add ~3 cm layer over the orange layer. Adding the mantle layer brings the ball up to a diameter of 6 centimeters.
4. Since it is difficult to make a sheet of clay less than one millimeter thick, use a thin layer of sand to represent the crust of the Earth. Ask student to carefully spread the sand, as evenly as possible, on a piece of paper on their desks. Then roll the ball in the sand.
5. Instruct groups to cut the ball in half using the fishing line. Opened up, students can visually understand the different layers and compare their thicknesses.

Students should not eat or put clay or Play-Doh® in their mouths.

Remind students how to read rulers before starting this activity.
It may be difficult for students to make the models small enough. Encourage them to measure each layer, before adding another. The following is a suggested method:
Although different people have different clay/Play-Doh® skills, they can achieve the same results. Create the outer core 3 cm in diameter using orange clay. Then, subtract clay from the outer core until you peel away enough clay the same size as the inner core (1 cm). Using the laws of addition, the red inner core plus the orange outer core that remains should equal 3 cm. Spread the remaining orange clay outer core out into a flat pancake. Wrap this around the inner core and roll the clay into a ball. Use the same idea to make the third and final layer.

Pre-Activity Assessment

Journal: On the attached Earthquakes Journal Page, have students write the four new vocabulary terms for the activity, inner core, outer core, mantle, and crust, into the "vocabulary" section. Ask students if they know what the terms mean. If they do not, define the terms together.
Discussion Question: Solicit, integrate and summarize student responses.
By building a scale model of the Earth, an engineer can design instruments that help predict earthquakes or think about how to invent robots to travel into the different layers. Why else might you want to create a scale model of the Earth? (Possible answers: To understand the size of the Earth in relation to other planets, to model space flight orbits involving the Earth, to search for locations to access natural gas, oil and geothermal energy, to predict how the Earth might change over time.)

Activity Embedded Assessment

Journal: Have students record their observations of the activity. Tell them all engineers record their observations and that an observation is anything that stands out as important. Ask students to write in anything they have learned or questions that they come up with throughout the model scaling activity.

Post-Activity Assessment

Journal: Have students complete the Earthquakes Journal Page for their binder.
Journey to the Center of the Earth: Show students various newspaper articles. Point out the typical newspaper article format and components, such as catchy headlines, short with relevant information only, most important information first. Tell students that they are engineers who have just invented a machine to take them to the core of the Earth. Their task is to write newspaper articles describing their discoveries as they travel through the layers of the Earth. Remind them to use descriptive words so the reader can visualize each layer of the Earth.
Homework: Assign students the Scale Model Homework Worksheet for homework.

Math Extension (for advanced math students):
1. Print out the attached Scaling Down the Earth – Math Extension Worksheet.
2. Pass out calculators.
3. Read the worksheet instructions aloud to the class.
4. Help students by going over the "Inner Core" as a class. Have them finish the rest of the worksheet independently.
5. Have students complete the table by calculating the actual diameters of the Earth's layers.
Have students research one or more of the following Earth layers subtopics:
• What are the minerals found in each layer of the Earth? How do these minerals relate to the state of matter of that layer?
• What are the temperatures of each layer of the Earth?
• Do any other planets have similar layers? If so, do they exhibit any earthquake or volcanic activity?

What do we know about the interior of the Earth? Last modified September 27, 2012. CoreFacts (audio), USGS Multimedia Gallery, US Geological Survey, US Department of the Interior. Accessed December 3, 2012. http://gallery.usgs.gov/audios/207#.ULywU2f543g

Robertson, Eugene C. The Interior of the Earth. Last modified January 14, 2011. US Geological Survey, US Department of the Interior. Accessed December 3, 2012. (A diagram of seismic waves and how they travel through the Earth's interior in this article [Figure 2] is a great graphic to support the information about S waves and how they travel through different layers.) http://pubs.usgs.gov/gip/interior/

Contributors

Jessica Todd, Melissa Straten, Malinda Schaefer Zarske, Janet Yowell, Jennifer Greever