Snacking on Plate Tectonics Author: Alicia Newton Overview: Students will use common snacks to understand plate boundaries and motion. Suggested grade level(s): 6 – 8 grades Concepts covered: Convergent and divergent plate boundaries, structure of the earth, differences between oceanic and continental plates Standards: S.C. Eighth Grade Sciences: III. 3 B. 1 c, d, e, and f 4. a and b Length of lesson: 30 minutes Materials required: 2 graham cracker squares ½ fruit roll-up 1- 1 foot square of wax paper large spoonful of frosting piece of popsicle stick or coffee stirrer cup of water (may be shared) Sheet of loose-leaf paper (per student) For 110 students you will need 5 boxes of graham crackers, 6 (10-count) boxes of fruit roll-ups, one roll of wax paper, and 11 cans of frosting. You might want to put these items on your beginning of the year “wish list” you send home to parents. Alternatively you could ask each student to bring two graham crackers and a fruit roll-up to class on the day of the activity and provide the frosting. Lesson Format Phase I. Engage Pass out The Earth Through Time worksheets. Have students follow the progress of North America (Laurentia) from 650 million years ago through the present and then follow its expected path in the future. How are the plates moving? Why are new mountain ranges occurring where some continents meet? Page 1 of 6 This lesson plan is part of the 2006 GK-12 Institute Phase II. Explore Have students recreate various plate boundaries using the materials: Fruit roll-up – oceanic crust Graham cracker – continental crust Frosting – asthenosphere To start each activity the students should spread their frosting into an approximately index card sized rectangle (1/4 to 1/2 inch thick) on their pieces of wax paper using the stirrer or popsicle stick. The students will need to carefully unroll their graham cracker halves and cut them in half again to form two approximately square pieces. FIGURE KEY Frosting Fruit roll-up Graham Cracker Damp Graham Cracker I. Divergent Plate Boundary Students will need two pieces of “oceanic crust.” They should place the two pieces of crust on the frosting with the edges touching. Explain that these two plates are being pulled apart. Have the students pull the pieces apart. Page 2 of 6 This lesson plan is part of the 2006 GK-12 Institute **Students should draw the results of the plate motion on their loose-leaf sheets. For this activity a profile view would be best. Student Question 1. What happens to the molten rock as the two pieces of crust move away from each other? The frosting, or molten rock, should rise up in between the plates as the move apart. Explain that this is how new oceanic crust is formed. Explain that two continental plates can also move away from each other, but it is less common. Student Question 2. If new crust is being created at these divergent boundaries, why isn’t the Earth expanding? This should lead students think about subduction zones and the recycling of crust. II. Transform Boundary Students will need the two pieces of continental crust. Place them side by side on the frosting. Push one plate up and the other down. **Students should draw the results of this activity in plan (bird’s-eye) view. Student Question 3. What happened to the edges of the graham crackers as they moved? The graham crackers crumbled slightly due to the friction of the two plates. Rocks at these boundaries can be crushed and broken. Because of the large amount of friction and pressure involved, energy can build up over time and be released in the form of earthquakes. Page 3 of 6 This lesson plan is part of the 2006 GK-12 Institute III. Convergent Plate Boundary (Oceanic – Continental) Students will need a piece of oceanic crust and a piece of continental crust (a fruit roll-up and a graham cracker). Line up the oceanic and continental crust on the frosting, making sure the oceanic crust is pressed firmly into the frosting and the continental is only lightly sitting on it. Gently push the pieces together. (The oceanic crust should slide underneath the continental). **Students should draw the result of this activity in profile. Student Question 4. What happened to the oceanic crust? Because the oceanic crust is more dense than the continental crust it subducted, or sank, beneath the continental crust. Student Question 5. Did the process happen smoothly? There was friction and some resistance on the part of the oceanic crust. Although they are often too deep to be felt by the people living on the Earth’s surface above them, earthquakes are common at modern subduction zones. However, the crust usually doesn’t wrinkle or ripple like the fruit roll-up did. Page 4 of 6 This lesson plan is part of the 2006 GK-12 Institute IV. Convergent Boundary (Continental – Continental) The students need two pieces of continental crust. They should soften one edge of each graham cracker by quickly dipping it in the water. Place the continental crust pieces on the frosting with the softened edges touching. Push the two pieces of crust together. (Mountain ranges should build along the margins. Some thrust faulting may also occur.) **Students should draw the results of this activity in profile. Student Question 6. What happened along the margins of the continental crust? Explain that as the continents collide, heat is generated. This heat softens the rock, which we mimicked by softening the graham crackers in water. At this point the students can eat their experiments. Page 5 of 6 This lesson plan is part of the 2006 GK-12 Institute Phase III. Explain The Earth is made up of a number of plates that move in the ways the students saw in the experiment. Use a map similar to this one from the USGS to identify real-world subduction and collision zones and transform boundaries. Students should recognize that these areas are associated with volcanoes and earthquakes. Phase IV. Elaborate Use this activity to introduce the structure of the Earth. Explain that the Earth has layers. The students should be able to relate the fruit roll-ups and graham crackers to the lithosphere and the frosting to the asthenosphere. Phase V. Evaluate A sample rubric is shown Category Questions Figures 4 All questions are answered thoughtfully, correctly, and in complete sentences Figures are neat and fully labeled. 3 Questions are answered correctly and in complete sentences 2 Answers are mostly correct 1 Answers are incorrect or not provided Figures are partially labeled Figures are drawn but not labeled No or only poor figures are provided Page 6 of 6 This lesson plan is part of the 2006 GK-12 Institute