Modeling Convection Currents
BACKGROUND INFORMATION:
The movement of heat from a warmer object or area to a cooler object or area is called heat transfer. Convection is heat transfer that takes place as the result of currents. Convection takes place within a fluid. Large amounts of heat are transferred through Earth via convection currents. Some of these currents are in Earth’s liquid outer core. Other convection currents are present in the mantle.
Convection currents in the mantle form and transfer heat as rock slowly rises toward the top of the mantle. The rock is still hard, but it flows very slowly like a fluid. As the rock rises, it cools and sinks back down into the mantle. As with all convection currents, convection in Earth’s mantle is the result of three things: heating and cooling of rock material, changes in the rock’s density, and the force of gravity.
Because it is not possible to directly observe the mantle, scientists sometimes make models to study how this part of Earth moves. Based on their findings, they make inferences and draw conclusions.
PROBLEM:
How might convection in the Earth’s mantle affect tectonic plates?
MATERIALS:
· Large glass beaker
· Small glass beaker
· Small pieces of paper
· Hot and cold tap water
· Aluminum foil
· Food coloring
· Rubber band
· Pencil with a sharp point
PROCEDURE:
1) Fill the large beaker about half full with cold tap water.
2) Fill the small beaker about ¾ full with hot tap water and stir in 5 drops of food coloring. Carefully add enough hot water to fill the small beaker to the brim.
3) Cover the top of the small beaker with aluminum foil and secure with a rubber band.
4) Carefully lower the small beaker into the large beaker of cold water.
5) Place the pieces of paper on the surface of the cold water.
6) Without disturbing the water, use the tip of the pencil to make two small holes about 2 mm in diameter in the aluminum foil covering the jar.
7) Observe the contents of the beaker and the paper pieces on the surface of the water.
8) After answering the questions below, throw away the pieces of paper, pour the water down the BACK sinks, and clean the dishes.
9) Make sure to clean your desk area!
OBSERVATIONS/ RESULTS:
1) Describe what happened to the colored water and to the pieces of paper after the holes were punched in the material covering the beaker.
2) What part of your model represented tectonic plates? What part represented the asthenosphere in the mantle?
3) What happened to the model tectonic plates? Did they all move together or apart? Did some move together and some move apart? How do explain these movements?
CONCLUSION:
How well do you think this lab modeled the movement of Earth’s plates? What similarities exist between this model and actual plate movement? What factors were you not able to model in this lab?