~Observing Convection Currents~
Background Information
Many scientists think that there are convection currents of hot rock within the mantle of the Earth. They think that the hot rock rises and flows out along the ridges. As this process goes on along the ridges, new ocean floor is created that pushes older ocean floor toward the continents. These scientists think that the continents are gradually moving because of these convection currents. In this investigation you will construct a working model of a convection current and study its action.
Problem
How can a model of a convection current be prepared and used to illustrate ocean-floor spreading?
Materials
1. Fill the beaker about three-fourths full with water.
2. Place the beaker into the beaker clamp and attach the clamp to the ring stand.
3. Light and adjust the flame on the burner.
4. Adjust the beaker on the ring stand so that the flame of the burner is directly heating only one side of the beaker.
5. When the water just begins to boil, add a few drops of food coloring. Draw a diagram of the beaker to show the path of the food coloring (convection current).
6. Turn off the burner and allow the water in the beaker to cool a little. Carefully sprinkle a fine layer of sawdust over the surface of the water.
7. Re-light your burner and adjust the flame. Heat one side of the beaker as you did in step 4.
8. Observe what happens to the sawdust as you look from above.
9. Turn off your burner. Allow your apparatus to cool completely before dismantling it.
What Happened and Why?
1. Explain the pattern formed by the food coloring.
2. Where was "new" water constantly being brought to the surface?
3. Describe and explain the motion of the sawdust.
4. How does the model you prepared compare to convection currents in the Earth's interior?
5. If two moving continents collided as a result of the convection currents that occurred beneath them, what changes might occur on the surface of the continents?
6. Why is it important for scientists to know where plate boundaries are located?
7. Make a large diagram of how a convection current might work deep under the ocean floor. Use posterboard, crayons, markers, or paint.
Link
Source: Prentice Hall Science Laboratory Manual for The Dynamic Earth; Copyright 1993. Adapted by: A. Miles and S. Vance; Rice Model Science Laboratory, Houston, TX.
