Demonstration: Model of Convection Currents

Objectives: in this demonstration you will see how convection currents may explain the driving forces behind plate tectonics.  Each student should record the prelab, data table and the analysis observations in their notebook.

Prelab:  Draw both of the diagrams side by side on the same page

1. Draw a diagram of a mid-oceanic ridge that includes how convection currents might move lithospheric plates.
2. Diagram the convection current demo and label the parts used.

Data Table:

	Thermometer A temp.	Thermometer B temp.	Thermometer C temp.
Minute zero
Minute five
Minute______w/sticks
Minute______

Analysis Observations:

1. What was the motion of the food color at minute zero?

2. Describe any differences in the food colors movement just after the candles have been lit.

3. Describe the motion of the food coloring after the candles have been lit for five minutes

4. What is the relationship between the motion of the sticks and the motion of the water?

5. Describe how the temperature of the water relates to the movement of the sticks/current.

6. In relation to the Earth’s interior what do the candles, water and sticks each represent?

7. Explain how the demonstration exemplifies the Earth’s interior convection currents.

Procedures:

1. Set up the experiment as shown.  Note:  The candles should be positioned about 2 cm away from the bottom of the metal pan.
2. Carefully fill the pan with cold water to a depth of at least 4 cm.
3. Imagine a line that divides the pan into half and carefully drop a single drop of food coloring over the location of the un-burning candles.  Use thermometer to Record data and observations #1
4. have the teacher lit your candles and leave the demo undisturbed for five minutes, then add a single drop of food coloring over each candle.  Use thermometer to Record data and observations #2
5. When tiny bubbles appear at the location over the candles (or after the candle has been burning for about 10 minutes total) carefully add a single drop of food coloring to the locations over the candles.  Use thermometer to Record data and observations #3
6. After a minute place the sticks about 3 cm to the side of the imaginary center line. 
7. As soon as the sticks begin to move add a single drop of food coloring to locations over the candles.  Use thermometer to Record data and observations.  #4
8. Clean up as instructed.

Candles/lamp

~2-3 cm from flame to the pan bottom

Water should be at 4-5 cm deep

Stand and ring clamp

A A

B

C

Locations for thermometers

Side View