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

TOPIC-TITLE Plate Tectonics - Why Does the Earth's Surface Move? AUTHOR George Linzee GRADE SUITABILITY Middle School SCOPE Earth Science

Sequence This activity is designed to follow a series of lessons that first present the geological features of the Earth's oceans and continents and then teach the theory of plate tectonics. By presenting a problem or aspect of a scientific theory scientists are still researching, this activity should stimulate and challenge students who are creative problem solvers. The teaching strategy includes presenting the problem and allowing students in cooperative learning groups to develop hypotheses. Then, student groups can conduct a demonstration that presents various hypotheses. Finally, the teacher can challenge the student groups to determine if they can design an experiment that may provide additional evidence for plate movement. < < go top

Background Summary he emergence of the plate tectonics theory has accounted for a broad range of geological features and events. While the concepts of plate movement and various boundary types have explained the formation of volcanoes, earthquakes, the construction of ocean mountains, island arc formations, ocean trenches, continental drift, and the rock cycle, the actual cause of the plate movement has not been firmly established. This lesson involves student cooperative learning groups in the consideration of internal convection cells as the driving force behind plate movement while also further substantiating the need for plate tectonics research. < < go top Objectives Students will be able to present and consider possible hypotheses that account for the movements of lithospheric plates in the Earth's crust. < < go top Materials One hot plate Graduated cylinder, 1,000 ml One tray of ice cubes Beakers, 1 and 2 liters Water source < < go top Activity Overview: review plate tectonics, describing all the features of the theory and using visual aids, such as maps of the Earth's surface and internal features. Hypothesis Generation: Present the questions, "Why do the plates move?" "What force causes the plates to move?" Give the student groups time to write their own ideas about probable causes. Then, allow each group to interact for 5 minutes. Each group should develop one hypothesis. Then, discuss each hypothesis (note: if convection has not been discussed, ask some leading questions that will allow convection discussion). Consideration of Convection Hypothesis: List, with student input, all the conditions necessary for convection to occur: heat source, fluid medium, and boundary conditions. Identify these elements in the structure of the Earth. Modeling Demonstration: Very carefully - using safety goggles and appropriate hand protection - pour 500 ml of water into the liter beakers and place them on a hot plate. Place six ice cubes in the middle of each beaker. Allow the convection cell to develop and spread the ice cubes in a manner similar to a divergent plate boundary. Stress that the ice is less dense than liquid water and corresponds to the rigid lithospheric plates floating over the fluid (glass-like) mantle. The hot plate corresponds to the Earth's internal sources of heat such as radioactive decay, pressure, and friction. Then, have students discuss what factors about the model do not account for the Earth's situation, such as it is too fast, does not rotate, wobble, or orbit like the Earth does. Further, this model does not have the gravitational effects of the moon or sun affecting it, nor is it receiving heat from the sun. Lastly, this model does not account for any magnetic field. < < go top Possible Extension Prepare a grant proposal: Each student can combine his/her final hypothesis and finalize experimental designs and/or research directions into a research grant proposal. The teacher should provide guidelines for grant proposals and be available for individual help. < < go top Teacher Evaluation Evaluate each student on his/her participation in class discussions. Questions: Are scientists confident that convection drives plate tectonics? Explain your answer. What internal layer of the Earth's structure has the fluid characteristics that would make convection possible? Why is it important to learn what makes the Earth's surface move? < < go top