Primary/Intermediate Science Resources - Classroom Activities

Activity: Earth Layers
(from Martin, Sexton, and Gerlovich, Science for All Children: Lessons for Constructing Understanding, 1999, p. 170-174.)

Concept to be invented
Main idea--The planet earth is made up of three layers: the core, mantle, and crust.

Concepts are important to expansion
Large land masses found on the crust of the earth are called continents. Large bodies of water are called oceans.

Materials needed
For exploration (one per student):
2-inch diameter ball of red, yellow and gray clay; plastic knife; white construction paper; three crayons of red, yellow, and gray.

For exploration (for entire class):
Green and blue clay, green crayon, globe of the earth, tennis ball, soccer ball. Maps of the ocean floors are useful but optional.

Safety precautions:
Remind students to be careful not to poke themselves or others with the plastic knife. Be sure to wash hands after using the clay. Remind them not to eat the clay.

1. Exploration: Which process skills will be used?

Observing, manipulating materials, predicting

What will the students do?
Clay Earth Layers
Guide the students through this portion of the lesson by first asking them to pick up the red clay and work it into a ball. Ask them to then flatten out the yellow clay and wrap it around the red ball of clay. Finally, ask them to flatten out the gray clay and then wrap it around the yellow-covered ball of clay. Ask the students to used their plastic knives carefully to cut the clay ball in half. Ask them to draw on their construction paper what the sliced-open ball of clay looks like.

2. Explanation/Concept Invention: What is the main idea? How will the main idea be constructed?

Concept: The planet earth is made up of three layers: the core, mantle, and crust.

Help the students invent the concept by asking them such questions as: What do you think this ball of clay with the different colored layers represents? Accept as many suggestions as possible and provide appropriate responses, all the while steering students toward thinking about the earth. If this suggestion is never given, then tell the students you'd like them to think of the clay ball as a representation of the earth and its layers. Since the students are most familiar with things found on the surface of the earth, ask them to give you suggestions of things they might find there. If possible, draw pictures of their suggestions, or write the names on the board. Ask if anyone has an idea for another name to call the earth's surface. You may make an analogy to a pie that has a different material on the inside than outside. What do you call the outer covering of the pie? Crust---this same name is given to the outer surface of the earth. As the students to label the gray layer on their diagram the crust.

Ask the students what they think the yellow layer may be like on the earth and if they have any ideas as to its name. The yellow clay represents the mantle. This layer of the earth is in a slightly liquid form. It is under enough pressure to heat the rock and melt it. Ask the sudents to label the yellow layer on their diagram the mantle.

Continue with questions to get the children to think about what the very middle of something is usually referred to. Get the students to think about what they call the center of an apple. The core is represented by the red ball. Because the core is under such great pressure it is very hot, but also in a solid state. Ask the students to label the red layer on their diagram the core.

3. Expansion of the Idea: Which process skills will be used?
Manipulating materials, observing, hypothesizing, inferring

How will the idea be expanded?

Clay Continents: Hold up the tennis ball. Ask the students how they think the tennis ball is like the earth. Encourage them to use the terms crust, mantle and core. Hold up a soccer ball. Ask the students how the soccer ball is like the earth. Hold up the globe. Tell them that this represents what the earth would look like if they were up in the sky looking down. Ask the students to observe the globe carefully. After they look at the globe, ask the students if they think the soccer ball or the tennis ball is more like the earth's surface. Engage the students in a conversation about how the soccer ball is not one solid piece, but many pieces sewn together. The crust of the earth does not look like one solid piece, but like many pieces separated by water. The pieces appear to fit together. Ask students for suggested names for the land masses and bodies of water. If none are given, tell the students that the land masses are called continents and the bodies of water are called oceans. If maps of the ocean floor are available, share them with the students. Be sure to point out that the crust still exists below the ocean water.

Provide the students with some green and blue clay. Ask them to put their two halves of clay back together again, gently sealing the gray clay so that they have one ball of clay again. Ask the students to use the green clay to place some masses or continents on their earth. Ask them to add blue clay between the continents to represent the oceans. Then ask them to use their green and blue crayons to draw the continents and oceans on their drawings and label them.

Science in Personal and Social Perspectives

• It has been found that the movement of the semi-liquid material in the mantle of the earth causes the crust to move. When the crust moves, earthquakes occur. Have earthquakes ever occurred where you live? What should be done to protect people during earthquakes?
• What continent do you live on?

Science and Technology

• How has knowledge about continent movement changed the way we construct buildings?
• Can earth quakes be detected? How?
• Do you think if technology could come up with a way to drain the oceans that would be better for life on earth? Why or why not?

Science as Inquiry

• Which layer of the earth is very hot yet still in a solid state?
• The land masses on the surface of the earth appear to fit together, yet many are far apart. Do you think they were once together? If so, why?
• Is there crust under the oceans? How do we know this?

History and Nature of Science

• A seismologist would need to understand that the earth is in layers. Why do you think this is true? What do you think a seismologist does?
• Should oceanographers be concerned about the earth's layers?
• Many oil companies get their oil out of the North Sea. Do you think these companies used their knowledge of the earth's layers to find their drilling sites? Why or why not?

4. Evaluation: How will the students show what they have learned?

• draw a diagram of a cross-section of the earth and label the continents, oceans, crust, mantle and core;
• identify from a diagram the different layers of the earth;
• explain how the earth can be compared to a soccer ball;
• point out continents and oceans on the globe.