Posts filed under ‘NGSS’

Model the Formation and Structure of the Earth. In one easy lab.

I used to think that geology was basically memorizing the layers of the Earth, and boring collections of rocks. Like most middle school science teachers, I’m a biologist by training and now I have to teach it with the integrated NGSS courses mandated in California. I’m getting more and more excited about the subject matter as I learn more, and hopefully passing that on to my classes.

I dreamed up this lab to help teach the underlying big-picture concepts for both layers of the Earth and an intro to plate tectonics. It went really well. Kids seemed lit up by the concepts and of course, stirring stuff and poking warm wax. I’m excited to share it with you. Not so excited about cleaning up the wax all over almost everything. But worth it. Really 🙂

So welcome to the sawdust, wax, sand and water jam-jar model of the Earth’s formation.

THE SET UP: Grate candles. Get sawdust (or beans will do) and sand. Have a couple of kettles. Boil ahead of time so the water is hot but not boiling. Have some non-slip oven hits. Have a box of ice. A quarter cup measure is handy for the sand and sawdust, a tablespoon of wax is enough. Mason jars or other heat-safe glass jars, one per table. Have a tub for students to wash out jars at the end so that wax and sand does not clog your sinks. Wash out the jars between each class.

SET THE CHALLENGE:

How did the Earth Form? – brief pair-share discussion to expose prior knowledge.

How does the Jam Jar Model relate to how the Earth formed and to the layers of the Earth? – The title they wrote in their journals.

THE DIRECTIONS:

Demonstrate: Put a scoop of grated candle wax, a scoop of sand and of saw dust in a Mason jar. Show how to use the hot water safely but don’t do that step or you’ll give it away. Have students wear eye protection when shaking or swirling the mixture.

Have one student from each group get the materials cafeteria style, Swirl it up. Add very hot water. Swirl some more. Let it settle and cool in the middle of the table. (Don’t do it for them, stop short of showing what happens.) I had students complete a poster of the layers of the Earth if they didn’t have enough to do – this is really a one-kid demo.

Show a video clip like this one from National Geographic “Birth of the Earth”, first 11 minutes.

Have students figure out how the settling and cooling ingredients relate to the real events that geologists think led to the formation of earth and the tectonic plates.

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Whiteboard lesson plan

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Students guessed the stages of earth’s formation on whiteboards

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As they waited for settling and cooling, they worked on earth layer posters

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Cafeteria-style collection of materials

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Comparing the model to the Earth layers.

 

SAFETY: Demonstrate how to use the hot water from the kettle – pour when the jar is on a counter or sink. Swirl, rather than shake up. Use eye protection and an oven glove during this process.

WRAP UP: Ask/discuss/write answers to these questions:

Why did the layers form? Use words like floating, sinking, density and buoyancy. The denser sand sinks to the bottom, then the sawdust, then the water and the least-dense wax floats on top. 

Compare the layers in the jam jar model to the layers of the Earth in a ‘t’ chart and/or as a diagram. See the illustration above. The densest minerals ‘sink’ to the center of gravity in the center of the Earth. The crust is the least dense – basalt and granite ‘float’ on top of the slowly convecting mantle minerals. 

How does this model relate to plate tectonics? The wax layer is thin and will break if there are currents swirling beneath, like the tectonic plates over the much more slowly convecting plastic mantle. 

How is this model NOT an accurate representation of the formation of the earth and it’s layers? The shape – it’s not spherical. The water is much more liquid than the mantle which is more plastic and convects very slowly. The sand is not radioactive and made mainly of iron and nickel etc. 

 

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January 7, 2019 at 5:43 PM Leave a comment


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