Sequence | Background | Objectives | Materials | Activity | Extensions | Evaluations

TOPIC-TITLE Plate Tectonics - There'll Be a Hot Time in the Old Core Tonight! AUTHOR Diane M. Smith GRADE SUITABILITY Middle School SCOPE Geosciences

Sequence You can use this lesson as a middle school unit on plate tectonics after the students have learned the size, shape, and position of land, and oceans can change as plates collide, slide, and move apart. The next logical step is for the students to learn how and why continental and oceanic plates change. < < go top

Background Summary The positions of the continental and oceanic plates change over time. These position changes are the result of heat exchanges or convection currents between the Earth's core and mantle. A convection current is an exchange of heat either in a liquid or a gas that results in the rise of magma through the mantle and into the crust, thereby forming an oceanic ridge (Greene, 1998). < < go top Objectives Students will be able to do the following: Create a model demonstrating the moving plates in the lithosphere. Draw diagrams explaining plate movements and changes. < < go top Materials (Per group of four students) Beaker, 400 ml Hotplate (or Bunsen burner, ring stand with "O" ring and clamp, and wire gauze square) Approximately one handful of small paper circles from a hole-punch Water A copy of Master 3.1a, The Inner Earth from Jason VI: Island Earth, Hawaii Expedition Curriculum < < go top Activity Note: The teacher will very carefully (wearing safety goggles and using appropriate gloves) demonstrate the activity to the students prior to the students performing the activity. Note: Students will also wear safety goggles and use appropriate heat-resistant gloves. Students will fill beakers with 200 ml of water. They will place the hole-punch circles into the water. Students will then place the beakers on hotplate or on the gauze squares held in the "O" ring clamps attached to their ring stands. If using Bunsen burners, students will light them and bring the water to near-boiling. Students should extinguish the flames (turn the gas off). Students will then observe the behavior of the hole-punch circles. Students will draw diagrams to use in their explanations of how the hole-punch circles moved. < < go top Possible Extension Using Styrofoam® balls, student groups could construct models of the layers of the Earth by cutting away one quarter of the ball, researching the thickness of each layer, and painting in each layer down to the core. The layers could then be keyed and labeled. Student groups could create charts to accompany the Styrofoam® models in extension. They should research the physical layer, the chemical layer, the depth below the surface, and the temperature and phase of each layer in a manner consistent with the chart given on page 118 of Jason VI: Island Earth, Hawaii, Expedition Curriculum. An appropriate extension of this lesson would be the "Hot Spots" lesson that follows the earlier lesson on convection currents. It is described on pages 126-127 of the Jason VI Curriculum and involves passing out Master 3.1b, Hot Spots, to each group of students. They are to align the arrows and tape the two pages together as indicated on the master and then cut the three windows. To show the action of the hot spot, they are to place the page with windows on top of the left-hand side of the second sheet. Students should align the submerged volcano so it can be seen clearly in the lower window and then carefully move the window sheet to the right. Stress the hot spot is an area in the Earth's mantle where rock from deep in the mantle is brought to the asthenosphere. Here, it melts, creating magma that rises through the lithosphere, reaching the surface and generating a volcanic eruption. When the plate moves, the hot spot may produce a new volcanic eruption and begin to form a new island. < < go top Teacher Evaluation Ask these questions: When the water is near-boiling, what happens to the hole-punch circles? (They move in a circular pattern.) Why does this happen? (As the water is heated, it rises. As it gets farther from the heat source, it cools and then sinks. The heat again causes the water to rise, and the cycle continues. This movement of heat in currents is called convection. The hole-punch circles simply move along with the convection currents as the solid rock does in the mantle.) How does this activity explain what happens within the mantle of the Earth? (This activity shows how heat can create and maintain a convection current.) Have students draw diagrams and make models using index cards to illustrate how the Pacific plate moves. They are to include convection currents and the hot spot under Hawaii. < < go top