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

TOPIC-TITLE Plate Tectonics - Seafloor Spreading AUTHOR Russell C. Read GRADE SUITABILITY Upper Elementary Middle School SCOPE Science

Sequence You can use these activities to introduce select principles concerning the Earth's internal processes. You should introduce plate tectonics before this activity. < < go top

Background Summary At the Earth's center is the inner core. Surrounding this is the outer core, the mantle, and the crust. The Earth's crust is divided into seven major and approximately twelve minor plates, including the Pacific, Nazca, North American, South American, Antarctic, African, Eurasian, and Indian. These plates float on top of the Earth's molten interior layer, and the continents "ride" on top of the plates (Greene, 1998). According to Greene (1998), a current is the transfer of heat in either a liquid or a gas that causes magma to rise through the mantle and into the crust and form oceanic ridges. Convection currents are believed to be the result of significant temperature differences between the upper and lower mantles. As magma moves under oceanic ridges, the oceanic plates move apart in a process called seafloor spreading (Greene, 1998). < < go top Objectives Students will be able to do the following: Observe the close fit of continental margins by cutting and piecing them together. Model the phenomenon of polar reversal with magnets and a compass. Relate the idea of convection currents as the driving force behind plate tectonics. < < go top Materials Tracing paper Pencils and pencil shavings Small world map Paper Bar magnets Compass Felt pens Shallow metal pans Hot plate Scissors < < go top Activity In cooperative learning groups: Students will use a sheet of tracing paper to trace the outline of the continents on a world map. Then, they will carefully cut the traced continents and diligently fit them together into one land mass. Compare results with the other student groups. Which continents seem to fit together best? Students should push two desks or two tables together and pull two sheets of paper in opposite directions through the tables that have been pushed together. Place the (N) poles of two magnets at the top of both papers where they exit the desk. Place a compass on the paper just below the magnets and draw an arrow on each sheet of paper in the direction of the compass needle. Pull the papers through the desktop or tables an inch on each side and reverse the magnets; again draw the direction of the arrows. Repeat this process three or four times. Students should discuss their results. As a demonstration performed very carefully by the teacher wearing goggles and using protective gloves, place a pan of water on a hot plate. Turn on the hot plate; heat the water a few minutes, and then sprinkle pencil shavings in the middle of the pan. Wearing goggles, students should observe the pattern of the shavings as they move out and away from the center of the pan. This is believed to be a result of convection currents. The teachers will add food coloring to the water with a pipette to better observe the movement of the water. Students should record all observations in a journal with a diagram depicting the results of both experiments. < < go top Possible Extension Fossil evidence or geologic formations could be integrated into this activity and could then be plotted on maps. The relationship between the rock cycle and plate tectonics could be discussed. Then, draw a plate tectonics diagram. < < go top Teacher Evaluation Journal can be graded for content and accuracy. Evaluate class discussion and comprehension of the topic. < < go top