Earth Lesson

Developing a Model of the Earth’s Inner Structure PROCESS/SKILLS: •

Observing

Creating

Describing

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Analyzing

Calculating

Recognizing patterns

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Estimating

Cooperating

Developing spatial sense

MATERIALS REQUIRED: •

A variety of fruits and vegetables (peach or nectarine, avocado, potato, orange, apple, grape, tomato)

•

Paper

•

Drawing compasses

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Calculators

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Clay (three different colors)

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Balances

OVERVIEW: How much do your students know about the Earth's interior? This learning cycle activity will provide them with a hands-on experience, as well as with appropriate terms and concepts. Students discover what makes a good model as they first choose a fruit or vegetable model and then create both a two-dimensional and three-dimensional model of the Earth's interior. The use proportion and estimation to build their three-dimensional models will also compare their various models for accuracy and overall utility. The learning cycle format includes three phases: space exploration (in which student exploration with concrete materials and problems allows them to make new connections with past experience), conceptual innovation (in which meaningful terms and concepts related to the exploration and experience are introduced), and conceptual expansion (in which students use the experience and concepts to progress in their understanding of the subject).

ACTIVITY OBJECTIVES: In the following activity, students will: •

Choose a good fruit or vegetable model of the earth and explain their reasoning.

•

Construct an accurate clay model of the earth, calculating or estimating the amount of cleaning it for each layer.

•

Effectively compare and analyze their various models of the Earth's inner structure.

BACKGROUND INFORMATION About the Earth's Inner Structure The earth is composed of three layers print on do (see figure 1). The core has an inner solid portion surrounded by liquid portion. The mantle is mostly solid rock, but also contains magma, or molten rock. The rocks of the cross create the continents and the ocean floors. The earth’s materials have been distributed based on their density with the heavier materials found near the planet’s center (the core being composed mostly of nickel and iron) and the lighter materials in the crust. The deepest that humans have bored into the Earth is at a geological test site in Siberia (more than 10 km deep). Most of what we know about the composition of the inner earth is based on studies of seismic waves (i.e., earthquake waves moving through rocks and monitored by laboratory instruments as they travel through the various layers of the planet). The deeper you go into the earth, the warmer the temperature becomes. The heat comes from the original heat that was generated when the planet was formed in from radioactivity. Plate tectonics refers to the movement of the plates in the crust, driven by convection of the mantle (the plates are pushed about by the hot, shuffling mantle underneath). The cross plates are constantly, but very slowly (because the plates usually move only a few centimeters each year), being created and destroyed. Where plates diverge, new crust is treated as magma rises from the mantle or plates converge, the leading edge of the crustal plate is pushed down and lost into the boundaries of tectonic plates, as they slide against one another. Figure 1. Earth’s inner structure

Main activity, step-by-step

1. Begin with a simple question: "What do you know about the inner structure of the earth?

That is, what is the Earth like on the inside?" Create a KWL (Know-Want to KnowLearned) chart by listing their response in the “Know” column of the chart. Fill in the next column of the chart by asking what they want to know about the Earth's inner structure and recording their responses. Keep this chart up throughout the activity and refer to it, clarifying knowledge, adjusting factual misconceptions, and pointing out connections to the students' areas of interest. 2. The exploration phase of the learning cycle is as follows: offer student groups a variety

of types of groups and vegetables (peach or nectarine, avocado, potato, space or edge, apple, grape, tomato, etc.) and ask them to choose the one that they think best represents the structure of the earth, especially considering what the plan is like on the inside. Be sure that they know they will be responsible for explaining their reasoning. Provide students with enough time to complete the task. 3. Now, to begin the conceptual invention phase of the learning cycle, asked each student

group to present its vegetable or fruit choice and rationale. Because the explanations will be based on very limited knowledge, ask what they need to know about the Earth to really pick the best piece of produce as an Earth model. List their responses on the board. They should want to know more about what the inside of the earth is like. Recall that the purpose of the conceptual invention phase is to build on the thoughts and findings from the exploration phase. Therefore, during and after their fruit/vegetable model presentations, explain the basics about the internal composition of our planet. Include the basic cross-section of core, mantle, and crust. 4. Proceed on to the conceptual expansion phase of the learning cycle by asking students

again which produce item is the best model of the earth, based on a new understanding of the facts. Ask each group to explain their answers in light of information about the Earth's inner structure. Did they choose a different produce item this time? Why or why not? Have each student draw a cross-section of the earth, labeling the core, mantle, and crust. Point out that this cross-sectional model is done in two dimensions (height and width). Also explain that they should base their drawings on the approximate diameters of each layer, which are as follows: Core = 3400 km; Mantle = 2900 km; Crust = 50 km Ask, "If you are going to make a three-dimensional, cross-sectional model of the earth, made from three different colors of clay (core = blue, mantle = red, crust = green), how much of each color would you need? That is, would you need more blue, red, or green, and can decide just how much you would need to make your ‘model earth’ in the cross-section?" Be sure each group can explain its rationale. As the student groups complete the calculations/estimates, offer clay and balances so they might weigh out the proper amount of each color and build their models. Groups can then compare and analyze their models for accuracy. Finally, ask students to determine and explain which is a better model of the earth's structure: the clay cross-

section or the piece of produce? Consider the sort of information each model offers, which model is most accurate, whether the model is practical (too small, too big, etc.) and any other considerations that come to mind. 5. Conclude with the "learned" column of the KWL chart: Ask what students learned during

this lesson and document their responses on the chart. What else do they want to know about the earth's interior?

Questions for discussion 1. Which fruit or vegetable was most like the earth? Which was least like the earth?

How do you know? 2. How did your group determine the amount of each color of clay needed for your

three-dimensional model of the earth? 3. How is your clay model like the earth? How is it different? 4. What makes something a good model of something else? What are some things to

consider when making a model of something?