Edible Tectonics
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Edible Tectonics

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Edible Tectonics Document Transcript

  • 1. Edible Tectonics Problem: How do the lithospheric plates move about on the earth’s surface, and what geologic features form as a result of that movement? Background: To understand plate tectonics, remember that the lithosphere is broken up into a number of plates. Some of these plates are large, while others are small. Although the plates touch, they move independently and are not connected to each other Geologists think the asthenosphere, a dense plastic-like layer of the upper mantle, is made of solid rock. The extreme heat and pressure cause the solid rock to move and flow. This flow causes convection currents as hot material rises and cooler material sinks. Rock in the asthenosphere flows about 2-3 cm every year. Because the lithosphere rides on top of the asthenosphere, flowing rock causes the plates to move. Plate tectonics is a unifying theory that explains many of Earth’s geological processes and physical features we see as we travel on Earth’s crust. In areas where the lithospheric plates move apart, for example, rift valleys along the crests of mid-ocean ridges can form. These types of boundaries are referred to as divergent boundaries and this is where magma forms new crust. Convergent boundaries are where two plates crash into each other. When two plates are approximately the same density, mountains form (e.g. the Himalayans). In areas where a more dense plate slides beneath another less dense plate, called a subduction zone, ocean trenches and volcanoes can form. In this case the plate that is being subducted is pushed back into the mantle to melt and go through the cycle again. A third type of plate boundary is known as a transform boundary. In this case the plates slide along each other parallel to each other. Edible Tectonics Problem: How do the lithospheric plates move about on the earth’s surface, and what geologic features form as a result of that movement? Background: To understand plate tectonics, remember that the lithosphere is broken up into a number of plates. Some of these plates are large, while others are small. Although the plates touch, they move independently and are not connected to each other Geologists think the asthenosphere, a dense plastic-like layer of the upper mantle, is made of solid rock. The extreme heat and pressure cause the solid rock to move and flow. This flow causes convection currents as hot material rises and cooler material sinks. Rock in the asthenosphere flows about 2-3 cm every year. Because the lithosphere rides on top of the asthenosphere, flowing rock causes the plates to move. Plate tectonics is a unifying theory that explains many of Earth’s geological processes and physical features we see as we travel on Earth’s crust. In areas where the lithospheric plates move apart, for example, rift valleys along the crests of mid-ocean ridges can form. These types of boundaries are referred to as divergent boundaries and this is where magma forms new crust. Convergent boundaries are where two plates crash into each other. When two plates are approximately the same density, mountains form (e.g. the Himalayans). In areas where a more dense plate slides beneath another less dense plate, called a subduction zone, ocean trenches and volcanoes can form. In this case the plate that is being subducted is pushed back into the mantle to melt and go through the cycle again. A third type of plate Boundary is known as a transform boundary. In this case the plates slide along each other parallel; to each other.
  • 2. .Procedures: A. Carefully unwrap the candy bar and use your fingernail or plastic fork to make a few cracks across the middle portion of its top. The cracked chocolate models the plates of the earth. 1. What layer of the earth does the chocolate represent? B. Hold the candy bar top facing up, with your left thumb and forefinger holding the sides of one end and your right thumb and forefinger holding the sides of the other. C. Slowly stretch the candy bar, pulling it apart a few millimeters at most. The chocolate should separate exposing the caramel. The exposed caramel represented new material that can rise to the earth’s surface. 2. What type of plate boundary is represented here? 3. What does the caramel represent (don’t say “new material that can rise…”)? D. Slowly push the stretched candy bar back together again. The brittle chocolate may crumble. On the other hand, “mountain ranges” may form when the pieces of the chocolate “plates” collide. Also, one chocolate “plate” may slide beneath another. 4. What type of plate boundary is represented here? 5. Be prepared to explain what you saw happen. E. Continue to slowly pull the candy bar apart and push it back together again. Do this until you have a good sense of how plates can be moved about by the motion of the caramel underneath. When the plates are pulled apart, material from beneath can move to the surface. When plates are pushed together they can collide, or one can slide beneath another. F. Once you have finished, pull the candy bar completely apart. Look at its exposed interior and think of the candy bar as a model of Earth’s layers. 6. Sketch the candy bar and label each layer of the bar with the corresponding layer of the earth. G. After answering the questions below, dispose of your model. If you have any reason you cannot eat the candy, please throw away your lab material. Otherwise you may eat your lab material. Conclusions in complete sentences: (Be sure you have completed the first six questions before continuing) 7. What geologic feature would you expect to see at a point where two plates are diverging?
  • 3. 8. What geologic feature would you expect to see at a point where two plates containing continental crust boundaries are converging? 9. What geologic feature would you expect to see where two plates containing oceanic crust boundaries are converging? 10. One limitation of this model is that human effort – your finger pulling and pushing – are not natural geologic processes. Explain the natural processes that cause the motion of the earth’s plates. 11. In your own words explain what the asthenosphere is. 12. A transform boundary was not modeled in this lab. Draw & label a picture and then describe how you could model one of these boundaries using the Milky Way bar. 13. Explain three ways this model is a good model of plate tectonics. 14. Explain three ways this model is not a good model of plate tectonics.
  • 4. Edible Tectonics Problem: How do the lithospheric plates move about on the earth’s surface, and what geologic features form as a result of that movement? Background: To understand plate tectonics, remember that the lithosphere is broken up into a number of plates. Some of these plates are large, while others are small. Although the plates touch, they move independently and are not connected to each other Geologists think the asthenosphere, a dense plastic-like layer of the upper mantle, is made of solid rock. The extreme heat and pressure cause the solid rock to move and flow. This flow causes convection currents as hot material rises and cooler material sinks. Rock in the asthenosphere flows about 2-3 cm every year. Because the lithosphere rides on top of the asthenosphere, flowing rock causes the plates to move. Plate tectonics is a unifying theory that explains many of Earth’s geological processes and physical features we see as we travel on Earth’s crust. In areas where the lithospheric plates move apart, for example, rift valleys along the crests of mid-ocean ridges can form. These types of boundaries are referred to as divergent boundaries and this is where magma forms new crust. Convergent boundaries are where two plates crash into each other. When two plates are approximately the same density, mountains form (e.g. the Himalayans). In areas where a more dense plate slides beneath another less dense plate, called a subduction zone, ocean trenches and volcanoes can form. In this case the plate that is being subducted is pushed back into the mantle to melt and go through the cycle again. A third type of plate boundary is known as a transform boundary. In this case the plates slide along each other parallel to each other. Procedures: H. Carefully unwrap the candy bar and use your fingernail or plastic fork to make a few cracks across the middle portion of its top. The cracked chocolate models the plates of the earth. 1. What layer of the earth does the chocolate represent? I. Hold the candy bar top facing up, with your left thumb and forefinger holding the sides of one end and your right thumb and forefinger holding the sides of the other. J. Slowly stretch the candy bar, pulling it apart a few millimeters at most. The chocolate should separate exposing the caramel. The exposed caramel represented new material that can rise to the earth’s surface. 2. What type of plate boundary is represented here? 3. What does the caramel represent (don’t say “new material that can rise…”)?
  • 5. K. Slowly push the stretched candy bar back together again. The brittle chocolate may crumble. On the other hand, “mountain ranges” may form when the pieces of the chocolate “plates” collide. Also, one chocolate “plate” may slide beneath another. 4. What type of plate boundary is represented here? 5. Be prepared to explain what you saw happen. L. Continue to slowly pull the candy bar apart and push it back together again. Do this until you have a good sense of how plates can be moved about by the motion of the caramel underneath. When the plates are pulled apart, material from beneath can move to the surface. When plates are pushed together they can collide, or one can slide beneath another. M. Once you have finished, pull the candy bar completely apart. Look at its exposed interior and think of the candy bar as a model of Earth’s layers. 6. Sketch the candy bar and label each layer of the bar with the corresponding layer of the earth. N. After answering the questions below, dispose of your model. If you have any reason you cannot eat the candy, please throw away your lab material. Otherwise you may eat your lab material. Conclusions in complete sentences: (Be sure you have completed the first six questions before continuing) 7. What geologic feature would you expect to see at a point where two plates are diverging? 8. What geologic feature would you expect to see at a point where two plates containing continental crust boundaries are converging? 9. What geologic feature would you expect to see where two plates containing oceanic crust boundaries are converging? 10. One limitation of this model is that human effort – your finger pulling and pushing – are not natural geologic processes. Explain the natural processes that cause the motion of the earth’s plates. 11. In your own words explain what the asthenosphere is. 12. A transform boundary was not modeled in this lab. Draw & label a picture and then describe how you could model one of these boundaries using the Milky Way bar. 13. Explain three ways this model is a good model of plate tectonics. 14. Explain three ways this model is not a good model of plate tectonics.